![[Feedback]](/icons/banner/feedbackACT.gif){kind=icon}
![[For Subscribers]](/icons/banner/subscriberACT.gif){kind=icon}
![[Archive]](/icons/banner/archiveACT.gif){kind=icon}
![[Search]](/icons/banner/searchACT.gif){kind=icon}
![[Contents]](/icons/banner/tocACT.gif){kind=icon}
Previous Article | Next Article 
Molecular and Cellular Biology, December 2003, p. 9073-9080, Vol. 23, No. 24
0270-7306/03/$08.00+0 DOI: 10.1128/MCB.23.24.9073-9080.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.
Department of Biochemistry, Hebrew University Hadassah Medical School, Jerusalem 91120, Israel
Received 26 March 2003/ Returned for modification 30 April 2003/ Accepted 27 August 2003
 |
ABSTRACT |
|---|
 Top Abstract IntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
|
INTRODUCTION |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
MITF regulates gene transcription by binding to E-box-type enhancers in the 5' flanking regions of MITF-responsive genes (25). Like many other DNA-binding proteins, the transcription-enhancing activity of MITF is influenced in a complex manner by an array of different intracellular proteins. For example, in vitro studies have indicated that MITF can form heterodimers with the four related family members TFEB, TFEC, TFE3, and USF2 (1, 3, 26, 41).
Other MITF-interacting proteins, PKCI/Hint (31) and PIAS3 (18), were previously identified using the yeast two-hybrid system with the bHLH-Zip domain as bait. These two MITF-associated proteins were shown to be repressors of MITF transcriptional activity (18, 31).
PIAS3 was initially found through its interaction with STAT3, whose transcriptional activity it inhibits (4). In vitro DNA-binding analysis suggested that PIAS3 can block the DNA-binding activity of STAT3 and thus inhibit STAT3-mediated gene activation (4). As mentioned above, the function of PIAS3 as a repressor of MITF-induced transcriptional activity has been demonstrated by inhibiting its DNA-binding activity, and it has been shown that STAT3 does not interfere either in vitro or in vivo with the interaction between PIAS3 and MITF (18). In order to further characterize the interaction between PIAS3 and MITF, we have determined the region within the bHLH-Zip domain that contains the site of interaction.
Phosphorylation-dephosphorylation of proteins is a key step in the regulation of protein-protein interactions. For instance, p300/CBP is an MITF transcriptional coactivator which can associate with MITF only in its MAPK-mediated phosphorylated form (29). Another example is the fact that tyrosine phosphorylation of STAT3 is a prerequisite for its interaction with other STAT proteins that allow the translocation of the STAT dimer into the nucleus, where it activates specific genes (32). Moreover, PIAS3 can heterodimerize with phosphorylated STAT3 only in order to block its DNA-binding activity (4). Therefore, it is likely that MITF participates in the coordinated expression of multiple genes by association-dissociation from proteins as a result of protein kinase-dependent phosphorylation.
Three serine sites for MITF phosphorylation have been reported (8, 35, 40). Phosphorylation of Ser73 (8) and Ser409 (40) occur as a result of Kit ligand stimulation and activation of MAPK and RSK-1, respectively. These serine sites are of interest, since upon their phosphorylation, MITF transcriptional activity is up regulated, and this phosphorylation also serves as a signal for the degradation of MITF by ubiquitin-dependent proteolysis in melanocytes (40). Ser298 is phosphorylated in vitro by GSK3ß, although it has the consensus sequence to be a MAPK phosphorylation site in vivo (35). Ser298 is one of the known mutation sites in Waardenburg syndrome type II (36). This site is located close to the bHLH-Zip domain, and its phosphorylation increases MITF binding activity in vitro (35).
The effect of MITF phosphorylation on its interaction with other proteins was further investigated in the present work. We determined how phosphorylation of three serine sites on MITF, 73, 298, and 409, regulates MITF transcriptional activity via its association with PIAS3. Phosphorylation of Ser409 was found to significantly decrease the association of MITF with PIAS3 and thus reconstituted its transcriptional activity. Moreover, in this work we demonstrate that the Zip domain of MITF contains the site of its interaction with PIAS3.
|
MATERIALS AND METHODS |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
Mice. Mouse colonies were established from transgenic mice (MITFsp/sp and MITFsp/di) kindly provided by Lynne Lamoreux from the College of Veterinary Medicine, Texas A&M University. The MITF encoded by the mutant midi allele lacks the Zip domain (7) due to a C-to-T transition in exon 8 at position 916, which introduces a premature stop codon between the bHLH and the leucine zipper domain.
Plasmid construction. Mouse MITF (1,129 bp) was subcloned into the XbaI and HindIII sites of the pcDNA3.1 (-) vector (Invitrogen). This vector was used for the production of all the MITF mutants by site-directed mutagenesis (Invitrogen), in which serine was replaced by aspartate at position 73, 298, or 409 (S73D, S298D, and S409D, respectively). Double mutation at serines 73 and 409 produced the S73/409D mutant. The cDNA encoding the open reading frame of mouse PIAS3 was subcloned into the XbaI and HindIII sites of the pcDNA3.1 (-) vector. Mouse MITF (1,129 bp) was inserted into the pGEX-4T-3 vector (Stratagene). The fidelity of all constructs was verified by direct sequencing. The luciferase reporter plasmid pSP72, containing the MITF binding region of the promoter and the first exon of the mMCP-6 gene (-191 to + 26), as well as a construct with a deleted MITF binding site (-151 to + 26), were generously provided by Y. Kitamura, Osaka, Japan. The pEBB-Mi (S409A) plasmid was kindly provided by David E. Fisher, Boston, Mass. A plasmid containing the constitutively active form of RSK (pk3h.rsk.y707a) was kindly provided by Tom Sturgill, Charlottesville, Va. (28).
Transient cotransfection and luciferase assay. NIH 3T3 cells (5 x 105) were cotransfected with liposomes (Promega) with 0.1 µg of the luciferase reporter, 0.1 µg of pcDNA-MITF, 0.1 µg of pcDNA-PIAS3, or 0.1 µg of pcDNA alone as a nonspecific control. The cells were incubated in 24-well plates for 48 h, lysed, and assayed for luciferase activity. The luciferase activity was normalized to the total protein concentration. The normalized value was then divided by the luciferase activity obtained by cotransfection of the reporter with pcDNA alone. The ratio was expressed as the relative luciferase activity.
Primers. The bacteriophage T7 transcription regulatory element and ribosome binding site were fused with the MITF primers. The pcDNA3.1 mouse MITF was used as a template. The basic-domain primers were as follows: sense, 5'-C TAA TAC GAC TCA CTA TAG GGA AGG AGA TAT ACA T ATG ATG CAG GGC CTG CCA CCG CCA GGC; antisense, 5'-TTA TCT TCT TCT TCG TTC AAT CAA GTT. The HLH domain primers used were as follows: sense, 5'-C TAA TAC GAC TCA CTA TAG GGA AGG AGA TAT ACA T ATG ATG TTT AAC ATA AAC GAC CGC ATT; antisense, 5'-TTA TTC CCG TTG CAA CTT CCG GAT GTA. The primers for the leucine zipper domain were as follows: sense, 5'-C TAA TAC GAC TCA CTA TAG GGA AGG AGA TAT ACA T ATG ATG CAG CAA CGA GCT AAG GAC CTT; antisense, 5'-TTA CAG CTC CTG TAC TCT GAG CAG CAG. The primers for the downstream leucine zipper domain were as follows: sense, 5'-C TAA TAC GAC TCA CTA TAG GGA AGG AGA TAT ACA T ATG ATG GAG ATG CAG GCT AGA GCG CA; antisense, 5'-TTA AAG TTC CTG GCT GCA GTT CTC AAG.
In vitro GST pull-down assay. The glutathionine S-transferase (GST)-PIAS3 fusion protein was expressed in protease-deficient Escherichia coli strain B12 and purified on glutathione-Sepharose beads (Amersham Biosciences) essentially as described before (18). Pull-down assays (6) were performed with the GST-PIAS3 fusion protein (1 to 5 µg) bound to Sepharose beads and preincubated for 1 h at 4°C in 1 ml of binding buffer (phosphate-buffered saline [PBS], 1 mM dithiothreitol, 1 mM EDTA, 5% glycerol, 0.1% NP-40). One to 10 µl of 35S-labeled full-length MITF (wild type or mutant) or its fragments were synthesized using the TNT-coupled rabbit reticulocyte lysate system (Promega) and then added to each preincubation mixture, and the binding reaction was carried out overnight at 4°C. Beads were washed four times in 1 ml PBS- 290 mM NaCl and boiled for 7 min in sample buffer, and aliquots were examined by electrophoresis. The integrity and quantity of GST fusions were confirmed by Blue stain reagent (Pierce), and autoradiography detected the amount of retained full-length MITF and its fragments.
Coimmunoprecipitation. BMMC derived from MITFdi/di and MITFsp/sp mice, BL6-B16 melanocyte cells, and NIH 3T3 cells were used in various coimmunoprecipitation experiments. BL6-B16 cells were cotransfected with MITF and PIAS3. NIH 3T3 cells were cotransfected with constitutively active RSK, PIAS3, and MITF, wild type or mutant. BL6-B16 cells were exposed to either 100 nM tetradecanoyl phorbol acetate (TPA) or 80 µg of c-kit ligand/ml (31) for up to 30 min (40). The cells (5 x 106 to 10 x 106) were lysed by the addition of 300 µl of cold lysis buffer (0.01 M Tris-HCl, pH 7.4, 1% deoxycholate, 1% Triton X-100, 0.1% sodium dodecyl sulfate [SDS], 0.15 M NaCl, and 0.25 µM phenylmethylsulfonyl fluoride) and 15 µl of protease inhibitors (Sigma). The cells were then homogenized, and their supernatants were collected after a 15-min centrifugation in a microcentrifuge at 4°C. The recovered lysates were incubated with either anti-mouse MITF antibody (31), MITF monoclonal antibody C5 (38), or anti-mouse PIAS3 antibody (Santa Cruz), prebound to 15 mg of protein A/G-agarose (Pierce), and incubated with agitation overnight at 4°C. Recovered immune complexes were washed three times with lysis buffer. All buffers contained protease inhibitors.
Gel electrophoresis and Western blotting. Proteins were resolved by SDS-10% polyacrylamide gel electrophoresis (PAGE) under reducing conditions and transferred to 0.45-µm-pore-size nitrocellulose membranes. The blots were probed with either anti-PIAS3, anti-MITF, or anti STAT3 (Santa Cruz) antibody. Visualization of reactive proteins was done by enhanced chemiluminescence (18).
Indirect fluorescent immunocytochemistry. c-kit ligand (50 µg/ml)-activated BL6-B16 cells were transfected with green fluorescent protein (GFP)-PIAS3 alone, whereas NIH 3T3 cells were cotransfected with GFP-PIAS3 and MITF, either wild type or mutant. The cells were grown on glass coverslips in six-well plates. After being extensively washed with PBS, the cells were fixed with 1.5 ml of 3.7% formaldehyde in PBS for 10 min. The fixed cells were then washed with PBS and permeabilized with 1.5 ml of Triton X-100 diluted 1:2 with PBS containing 7.5 mg of bovine serum albumin. After being blocked for 45 min with normal donkey serum, the cells were stained with rabbit anti-MITF (26) followed by the addition of Red-Cy5-conjugated goat anti-rabbit immunoglobulin G (Jackson ImmunoResearch). Fluorescence analysis was performed using the Zeiss LSM 410 confocal laser scanning system connected to a Zeiss Axiovert 135 M microscope. The green fluorescence of GFP-labeled PIAS3 was excited with an argon laser (488-nm excitation line with 515-nm long pass barrier filter). Red-Cy5-conjugated goat anti-rabbit antibody was simultaneously excited with an He-Ne laser (543-nm excitation line with 570-nm long pass barrier filter).
|
RESULTS |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
|
In order to determine the relative amounts of these three proteins in BMMC derived from MITFdi/di mice compared to BMMC derived from MITFsp/sp mice, Western blot analysis was performed. The blots were probed with anti-MITF, anti-PIAS3, or anti-STAT3 antibody. No significant change in the cellular concentrations of these proteins was observed in cells derived from the mutated mice (Fig. 1D).
Thus, the results obtained from the pull-down assay, together with those obtained from cells derived from the MITF-truncated mice, clearly indicate that the MITF Zip domain plays an essential role in the interaction between MITF and PIAS3.
Dynamic association of MITF and PIAS3 in activated cells. The subcellular localization of MITF and PIAS3 in c-kit ligand-activated BL6-B16 cells was determined using confocal laser scanning analysis. The cells were transfected with PIAS3 that was constructed with GFP (GFP-PIAS3) or with GFP alone. Resting and activated cells were fixed and stained with rabbit anti-MITF antibody, which was detected by staining with Red-Cy5-conjugated goat anti-rabbit antibody (Fig. 2A). MITF and PIAS3 were located in both the nuclei and the cytosol of resting (Fig. 2A, I) and activated (Fig. 2A, II and III) cells; however, a clear increase in the nuclear colocalization of these two proteins in the transfected cells was seen after the melanocytes were activated by c-kit ligand for 10 min (Fig. 2A, II). Thirty minutes after activation, a decrease in this colocalization was observed (Fig. 2A, III). Interaction between the two proteins was also observed in the nuclei of the resting cells, but to a much lesser extent. Thus, activation of melanocytes for 10 min induced an increase in the association between PIAS3 and MITF, which was reduced by 30 min of activation.
|
The amounts of PIAS3 bound to the beads were similar at all time points (Fig. 2B). Western blots of the same cell lysates were probed with anti-MITF antibody. Similar amounts of MITF were observed 10 and 30 min after TPA activation (Fig. 2B).
A similar pattern of disassociation was seen after 10 min of activation with c-kit ligand (data not shown).
Involvement of MITF-dependent RSK phosphorylation in its interaction with PIAS3. It was previously reported that MITF is phosphorylated by RSK at serine 409 (23). In order to evaluate the role played by RSK in MITF-PIAS3 interactions, NIH 3T3 cells were cotransfected with a constitutively active RSK plasmid (28), with a luciferase reporter plasmid containing the mMCP-6 promoter, and with either MITF or an S409A MITF mutant which cannot be phosphorylated by RSK. The transcriptional activity of MITF was determined as relative luciferase activity. No significant change in such activity was detected regardless of whether the cells were transfected with MITF or its mutated form with or without RSK (Fig. 3A).
|
Phosphorylation of MITF at S409 interferes with PIAS3 interaction. We chose to evaluate the serine sites in MITF, the biological effects of whose phosphorylation have already been studied in other systems (8, 40, 35). These serine sites are localized at position 73, which is 40 amino acids upstream of the N terminus activation domain; at position 409, which is 40 amino acids downstream of the C terminus activation domain; and at position 298, which is located 9 amino acids after the termination of the Zip domain (33). Site-directed mutagenesis was performed for these three well-characterized MITF phosphorylation sites by replacing the serine with aspartate. Such an amino acid substitution of aspartate for serine can be used to mimic the charge brought by the phosphate group (11, 39).
PIAS3 was expressed in bacteria as a GST fusion protein, immobilized on glutathione-Sepharose beads, and assayed by pull-down assay for its ability to retain in vitro-translated wild-type MITF and its mutants (S73D, S298D, S409D, and S73/409D), which were labeled with [35S]methionine (Fig. 4). More MITF mutant S73D than wild-type MITF or mutant S298D bound to PIAS3. No interaction was observed between PIAS3 and the MITF mutant S409D, whereas double-mutated MITF, S73/409D, showed a slight decrease in binding to PIAS3 compared to S73D. Similar amounts of the in vitro-translated MITF were seen in the various forms of MITF. The GST pull-down alone did not interact with either wild-type MITF or its mutants (data not shown).
|
|
Replacement of S409 in MITF with aspartate significantly reduced its transcriptional inhibition by PIAS3. In order to find out how phosphorylation of MITF regulates the inhibition of its transcriptional activity by PIAS3, we first determined the transcriptional activity of the mutated MITF in which aspartate was substituted for specific serines. NIH 3T3 fibroblasts, which do not abundantly express endogenous MITF, were cotransfected with a luciferase reporter plasmid containing the mMCP-6 promoter and pcDNA constructs of either MITF or MITF mutants. All the mutated MITF forms showed an increase in luciferase activity compared to the cells transfected with wild-type MITF (data not shown).
The role played by MITF phosphorylation in the suppression of its transcriptional activity by PIAS3 was then determined. NIH 3T3 cells were cotransfected with a luciferase reporter plasmid containing the mMCP-6 promoter and 0.1 µg of pcDNA constructs of either MITF or mutated MITF (S73D, S298D, or S409D) and with 0.1 µg of PIAS3 (Fig. 6). The levels of inhibition of transcriptional activity were similar when PIAS3 was cotransfected with either wild-type MITF or its S298D mutant (49% ± 2% and 42% ± 1%, respectively). A slight increase in the transcriptional inhibition of MITF by PIAS3 (69% ± 5%) was observed with the S73D MITF mutant. Almost no inhibition (5% ± 1%) in MITF transcriptional activity was observed when cells were cotransfected with the MITF mutant S409D and PIAS3. All of the results are expressed as the mean ± standard error of three experiments. Double mutation of MITF at S73 and S409 brought the transcriptional inhibition by PIAS3 into the same range as that achieved with the wild-type MITF; however, there was less inhibition by PIAS3 than by the S73D mutant alone.
|
|
DISCUSSION |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
To evaluate the role played by MITF phosphorylation at serines at positions 298, 73, and 409 in its interaction with PIAS3, we constructed MITF mutants in which these serines were replaced by an aspartate, which mimics the charge brought by the phosphate group (11, 39). These constitutively phosphorylated mutants of MITF were cotransfected into NIH 3T3 fibroblasts with a luciferase reporter plasmid containing the mMCP-6 promoter, and the luciferase activity was enhanced in all three of the mutants. Aspartate substitution at serine 73 of MITF resulted in a slight increase in its association with PIAS3, whereas substitution at serine 409 almost totally abolished the capability of MITF to interact with PIAS3. These results strongly indicate that phosphorylation of MITF plays a role as an alternative transcriptional pathway, mediated either by the release of MITF from the PIAS3 inhibitor or by stronger interaction between the two proteins.
We further showed that RSK, which is known to phosphorylate MITF at position 409 (40), caused dissociation between MITF and PIAS3 and therefore a decrease in PIAS3-mediated MITF transcriptional activity. Moreover, when the S409A mutant, a mutant which has been found to be resistant to phosphorylation by RSK (23), was used, no change was observed in the PIAS3-MITF(S409A) association.
It has been reported that in melanocytes, replacement of Ser73 or Ser409 of MITF by alanine caused suppression of Kit ligand-mediated transcriptional activity (40). This suggests that phosphorylation at these serines is sufficient to signal ubiquitin-dependent proteolysis of this transcription factor (40). These results, together with our data, indicate that serine phosphorylation at these positions regulates MITF activity directly via transcriptional activation and MITF degradation and indirectly via its interaction with PIAS3.
MITF has several potential sites for protein-protein interaction in the bHLH-Zip motifs. The bHLH-Zip domain of MITF is essential for the expression of the mMCP-6 gene (27), and the Zip domain of MITF has been found to be important for the development and differentiation of mast cells (24). In the present work, we demonstrated that the MITF Zip region is the domain responsible for direct interaction with PIAS3, which is a zinc finger protein (20). This Zip domain has recently been found to be responsible for the association of MITF with another zinc finger protein, myc-associated zinc finger-related factor (23). This association leads to the enhancement of MITF transcriptional activity (23). Previous work revealed that PIAS3 interacts directly with MITF and suppresses its transcriptional activity (18). The Zip domain of MITF contains several charged residues that upon phosphorylation play critical roles in the process of molecular recognition (33). Furthermore, this domain appears to be essential for interaction and DNA binding (9). Although serine 298 in MITF is located right after the Zip domain, we have focused in this work on the role of serines 73 and 409, which are not located in proximity to this domain, in the MITF-PIAS3 interaction (33). Thus, we assume that the phosphorylation on these two MITF serine residues induces conformational changes in MITF that allow the recruitment of some other proteins to the complex and thereby modulate the strength of the interaction.
The association between Jak-mediated phosphorylated STAT3 and PIAS3 has been thoroughly investigated (17). It is known that activation causes phosphorylation of STAT3, which then binds to PIAS3. We assume that MITF is similarly phosphorylated upon activation. In our colocalization experiments, we did indeed see greater nuclear interaction in cells activated for 10 min than in resting cells or cells activated for 30 min. However, we have also shown the inability of PIAS3 to associate with S409-phosphorylated MITF, which presumably mimics the phosphorylation that occurs upon cell activation. MAPK-mediated phosphorylation, which occurs at serine 73, has been shown to be maximal after 10 min of activation (40). In contrast, Rsk-1-mediated phosphorylation, which occurs at serine 409, was shown to be maximal at 20 min (40). This presumably explains why we observed increased colocalization of PIAS3 and MITF 10 min after activation, when most phosphorylation is occurring at S73 as opposed to S409, whereas 30 min after activation, both colocalization and coimmunoprecipitation of these proteins were reduced.
These results shed new light on the intracellular shuttling of PIAS3 from one cellular component to another. Moreover, we demonstrated a decrease in vivo in the interaction between MITF and PIAS3 in mast cells derived from MITFdi/di mice, which lack the Zip domain in MITF (7). The interaction between the two proteins in cells derived from these mutated mice was not completely abolished, suggesting that there is some other protein(s) involved in this interaction. Furthermore, the slight increase in PIAS3-STAT3 association in cells derived from these MITF-truncated mice indicates that MITF plays a significant role in STAT3-mediated gene expression.
STAT3 is a latent transcription factor and a major molecule in the STAT family, which mediates cytokine- and growth factor-directed transcription. In a variety of hematopoietic derived cells, receptor stimulation leads to phosphorylation of tyrosine residues of STAT, which rapidly triggers DNA binding and STAT-mediated gene transcription (4, 16, 32). Interestingly, the binding of PIAS3 to STAT3 is induced following its phosphorylation, perhaps acting as a feedback mechanism preventing overactivation of this transcription factor (4). It was previously reported that STAT3 does not associate with PIAS3 that is already associated with MITF (18). Thus, while STAT3 phosphorylation leads to PIAS3 binding and inactivation of STAT3, the phosphorylation of MITF on serine 409 leads to the release of PIAS3, which can then potentially bind to STAT3. Thus, phosphorylation is a fine tuning of the regulation of the transcriptional machinery by the same inhibitor in a very different fashion. Further research will focus on whether the same motifs in PIAS3 are responsible for its association with STAT3 and MITF.
The oncogenic properties of constitutively active STAT3 offer an explanation for the ability of MITF to increase its transcriptional activity in melanoma (5). This activated STAT3 might induce the recruitment of PIAS3 into the STAT system and thus indirectly increase the transcriptional activity of MITF. This up regulation of MITF by STAT activation could be considered an indirect pathway for increasing transcriptional activity.
In conclusion, we suggest that the Zip region and phosphorylation of MITF at serine 409 play novel roles in the inhibition of activation of MITF transcriptional activity.
|
ACKNOWLEDGMENTS |
|---|
Carmit Levy and Amir Sonnenblick contributed equally to this work.
|
FOOTNOTES |
|---|
|
REFERENCES |
|---|
|
TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
|---|
2. Bentley, N. J., T. Eisen, and C. R. Goding. 1994. Melanocyte-specific expression of the human tyrosinase promoter: activation by the microphthalmia gene product and role of the initiator. Mol. Cell. Biol. 14:7996-8006.
3. Carr, C. S., and P. A. A. Sharp. 1990. Helix-loop-helix protein related to the immunoglobulin E box-binding proteins. Mol. Cell. Biol. 10:4384-4388.
4. Chung, C. D., J. Liao, B. Liu, X. Rao, P. Jay, P. Berta, et al. 1997. Specific inhibition of Stat3 signal transduction by PIAS3. Science 278:1803-1805.
5. Dorvault, C. C., K. N. Weilbaecher, H. Yee, D. E. Fisher, L. A. Chiriboga, Y. Xu, and D. C. Chhieng. 2001. Microphthalmia transcription factor: a sensitive and specific marker for malignant melanoma in cytologic specimens. Cancer 93:337-343.[CrossRef][Medline]
6. Goldstein, R. E., G. Jimenez, O. Cook, D. Gur, and Z. Paroush. 1999. Huckebein repressor activity in Drosophila terminal patterning is mediated by Groucho. Development 126:3747-3755.[Abstract]
7. Hallsson, J. H., J. Favor, C. Hodgkinson, T. Glaser, M. L. Lamoreux, R. Magnusdottir, et al. 2000. Genomic, transcriptional and mutational analysis of the mouse microphthalmia locus. Genetics 155:291-300.
8. Hemesath, T. J., E. R. Price, C. Takemoto, T. Badalian, and D. E. Fisher. 1998. MAP kinase links the transcription factor Microphthalmia to c-Kit signalling in melanocytes. Nature 391:298-301.[CrossRef][Medline]
9. Hemesath, T. J., E. Steingrimsson, G. McGill, M. J. Hansen, J. Vaught, C. A. Hodgkinson, et al. 1994. Microphthalmia, a critical factor in melanocyte development, defines a discrete transcription factor family. Genes Dev. 8:2770-2780.
10. Hodgkinson, C. A., K. J. Moore, A. Nakayama, E. Steingrimsson, N. G. Copeland, N. A. Jenkins, et al. 1993. Mutations at the mouse microphthalmia locus are associated with defects in a gene encoding a novel basic-helix-loop-helix-zipper protein. Cell 74:395-404.[CrossRef][Medline]
11. Hoeffler, W. K., A. D. Levinson, and E. A. Bauer. 1994. Activation of c-Jun transcription factor by substitution of a charged residue in its N-terminal domain. Nucleic Acids Res. 22:1305-1312.
12. Hughes, M. J., J. B. Lingrel, J. M. Krakowsky, and K. P. A. Anderson. 1993. Helix-loop-helix transcription factor-like gene is located at the mi locus. J. Biol. Chem. 268:20687-20690.
13. Isozaki, K., T. Tsujimura, S. Nomura, E. Morii, U. Koshimizu, Y. Nishimune, and Y. Kitamura. 1994. Cell type-specific deficiency of c-kit gene expression in mutant mice of mi/mi genotype. Am. J. Pathol. 145:827-836.[Abstract]
14. Ito, A., E. Morii, D. K. Kim, T. R. Kataoka, T. Jippo, K. Maeyama, H. Nojima, and Y. Kitamura. 1999. Inhibitory effect of the transcription factor encoded by the mi mutant allele in cultured mast cells of mice. Blood 93:1189-1196.
15. Ito, A., E. Morii, K. Maeyama, T. Jippo, D. K. Kim, Y. M. Lee, H. Ogihara, K. Hashimoto, Y. Kitamura, and H. Nojima. 1998. Systematic method to obtain novel genes that are regulated by mi transcription factor: impaired expression of granzyme B and tryptophan hydroxylase in mi/mi cultured mast cells. Blood 91:3210-3221.
16. Junicho, A., T. Matsuda, T. Yamamoto, H. Kishi, K. Korkmaz, F. Saatcioglu, H. Fuse, and A. Muraguchi. 2000. Protein inhibitor of activated STAT3 regulates androgen receptor signaling in prostate carcinoma cells. Biochem. Biophys. Res. Commun. 278:9-13.[CrossRef][Medline]
17. Kile, B. T., N. A. Nicola, and W. S. Alexander. 2001. Negative regulators of cytokine signaling. Int. J. Hematol. 73:292-298.[Medline]
18. Levy, C., H. Nechushtan, and E. A. Razin. 2002. New role for the STAT3 inhibitor, PIAS3: a repressor of microphthalmia transcription factor. J. Biol. Chem. 277:1962-1966.
19. McGill, G. G., M. Horstmann, H. R. Widlund, J. Du, G. Motyckova, E. K. Nishimura, Y. L. Lin, S. Ramaswamy, W. Avery, H. F. Ding, S. A. Jordan, I. J. Jackson, S. J. Korsmeyer, T. R. Golub, and D. E. Fisher. 2002. Bcl2 regulation by the melanocyte master regulator Mitf modulates lineage survival and melanoma cell viability. Cell 109:707-718.[CrossRef][Medline]
20. Mohr, S. E., and R. E. Boswell. 1999. Zimp encodes a homologue of mouse Miz1 and PIAS3 and is an essential gene in Drosophila melanogaster. Gene 229:109-116.[CrossRef][Medline]
21. Moore, K. J. 1995. Insight into the microphthalmia gene. Trends Genet. 11:442-450.[CrossRef][Medline]
22. Morii, E., T. Jippo, K. Hashimoto, D.-K. Kim, Y.-M. Lee, H. Ogihara, K. Tsujino, and H. M. Kim. 1997. Abnormal expression of mouse mast cell protease 5 gene in cultured mast cells derived from mutant mi/mi mice. Blood 90:3057-3066.
23. Morii, E., K. Oboki, T. R. Kataoka, K. Igarashi, and Y. Kitamura. 2002. Interaction and cooperation of mi transcription factor (MITF) and myc-associated zinc-finger protein-related factor (MAZR) for transcription of mouse mast cell protease 6 gene. J. Biol. Chem. 277:8566-8571.
24. Morii, E., H. Ogihara, K. Oboki, T. R. Kataoka, K. Maeyama, D. E. Fisher, M. L. Lamoureux, and Y. Kitamura. 2001. Effect of a large deletion of the basic domain of mi transcription factor on differentiation of mast cells. Blood 98:2577-2579.
25. Morii, E., T. Tsujimura, T. Jippo, K. Hashimoto, K. Takebayashi, K. Tsujino, S. Nomura, M. Yamamoto, and Y. Kitamura. 1996. Regulation of mouse mast cell protease 6 gene expression by transcription factor encoded by the mi locus. Blood 88:2488-2494.
26. Nechushtan, H., Z. Zhang, and E. Razin. 1997. Microphthalmia (mi) in murine mast cells: regulation of its stimuli-mediated expression on the translational level. Blood 89:2999-3008.
27. Ogihara, H., E. Morii, D. K. Kim, K. Oboki, and Y. Kitamura. 2001. Inhibitory effect of the transcription factor encoded by the mutant mi microphthalmia allele on transactivation of mouse mast cell protease 7 gene. Blood 97:645-651.
28. Poteet-Smith, C. E., J. A. Smith, D. A. Lannigan, T. A. Freed, and T. W. Sturgill. 1999. Generation of constitutively active p90 ribosomal S6 kinase in vivo. Implications for the mitogen-activated protein kinase-activated protein kinase family. J. Biol. Chem. 274:22135-22138.
29. Price, E. R., H. F. Ding, T. Badalian, S. Bhattacharya, C. Takemoto, T. P. Yao, T. J. Hemesath, and D. E. Fisher. 1998. Lineage-specific signaling in melanocytes. C-kit stimulation recruits p300/CBP to microphthalmia. J. Biol. Chem. 273:17983-17986.
30. Razin, E., C. Cordon-Cardo, and R. A. Good. 1981. Growth of a pure population of mouse mast cells in vitro with conditioned medium derived from concanavalin A-stimulated splenocytes. Proc. Natl. Acad. Sci. USA 78:2559-2561.
31. Razin, E., Z. C. Zhang, H. Nechushtan, S. Frenkel, Y. N. Lee, R. Arudchandran, and J. Rivera. 1999. Suppression of microphthalmia transcriptional activity by its association with protein kinase C-interacting protein 1 in mast cells. J. Biol. Chem. 274:34272-34276.
32. Shuai, K. 2000. Modulation of STAT signaling by STAT-interacting proteins. Oncogene 19:2638-2644.[CrossRef][Medline]
33. Tachibana, M. 2000. MITF: a stream flowing for pigment cells. Pigment Cell Res. 13:230-240.[CrossRef][Medline]
34. Tachibana, M., K. Takeda, Y. Nobukuni, K. Urabe, J. E. Long, K. A. Meyers, S. A. Aaronson, and T. Miki. 1996. Ectopic expression of MITF, a gene for Waardenburg syndrome type 2, converts fibroblasts to cells with melanocyte characteristics. Nat. Genet. 14:50-54.[CrossRef][Medline]
35. Takeda, K., C. Takemoto, I. Kobayashi, A. Watanabe, Y. Nobukuni, D. E. Fisher, and M. Tachibana. 2000. Ser298 of MITF, a mutation site in Waardenburg syndrome type 2, is a phosphorylation site with functional significance. Hum. Mol. Genet. 9:125-132.
36. Tassabehji, M., V. Newton, X. Liu, A. Brady, D. Donnai, M. Krajewska-Walasek, et al. 1995. The mutational spectrum in Waardenburg syndrome. Hum. Mol. Genet. 4:2131-2137.
37. Tassabehji, M., V. E. Newton, and A. P. Read. 1994. Waardenburg syndrome type 2 caused by mutations in the human microphthalmia (MITF) gene. Nat. Genet. 8:251-255.[CrossRef][Medline]
38. Weilbaecher, K. N., C. L. Hershey, C. M. Takemoto, M. A. Horstmann, T. J. Hemesath, A. H. Tashjian, and D. E. Fisher. 1998. Age-resolving osteopetrosis: a rat model implicating microphthalmia and the related transcription factor TFE3. J. Exp. Med. 187:775-785.
39. Wittekind, M., J. Reizer, J. Deutscher, M. H. Saier, and R. E. Klevit. 1989. Common structural changes accompany the functional inactivation of HPr by seryl phosphorylation or by serine to aspartate substitution. Biochemistry 28:9908-9912.[CrossRef][Medline]
40. Wu, M., T. J. Hemesath, C. M. Takemoto, M. A. Horstmann, A. G. Wells, E. R. Price, D. Z. Fisher, and D. E. Fisher. 2000. c-Kit triggers dual phosphorylations, which couple activation and degradation of the essential melanocyte factor Mi. Genes Dev. 14:301-312.
41. Zhao, G. Q., Q. Zhao, and X. Zhou. 1993. TFEC, a basic helix-loop-helix protein, forms heterodimers with TFE3 and inhibits TFE3-dependent transcription activation. Mol. Cell. Biol. 13:4505-4512.
This article has been cited by other articles:
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| J. Bacteriol. | J. Virol. | Eukaryot. Cell |
|---|
| Microbiol. Mol. Biol. Rev. | Clin. Vaccine Immunol. | All ASM Journals |
|---|
-PIAS3), and the blot was probed with either anti-MITF or anti-STAT3 antibody, stripped, and reprobed with anti-PIAS3 antibody. One representative of three experiments is shown. (D) Western blot (WB) analysis of BMMC lysates derived from MITFsp/sp or MITFdi/di mice. One representative of two experiments is shown.
