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Molecular and Cellular Biology, September 1999, p. 6195-6206, Vol. 19, No. 9
Graduate Institute of Life Science,
Received 16 February 1999/Returned for modification 30 March
1999/Accepted 21 June 1999
mcl-1 is an immediate-early gene activated by the
granulocyte-macrophage colony-stimulating factor (GM-CSF) and
interleukin 3 (IL-3) signaling pathways and plays an important role in
the viability response of these cytokines. In this study, we
demonstrated that cytokine stimulation of mcl-1 mRNA and
protein expression were attenuated by pretreatment of cells with
phosphatidylinositol 3-kinase (PI3-K) inhibitors. Reporter gene assays
further showed that the PI3-K/Akt signaling pathway was involved in
IL-3 activation of mcl-1 gene transcription. Analysis of
the mcl-1 promoter revealed that both promoter elements,
SIE at position
0270-7306/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
The Antiapoptotic Gene mcl-1 Is
Up-Regulated by the Phosphatidylinositol 3-Kinase/Akt Signaling Pathway
through a Transcription Factor Complex Containing CREB
87 and CRE-2 at
70, contribute to IL-3 stimulation
of mcl-1 gene expression. Although either the SIE site or
the CRE-2 site alone was sufficient to confer IL-3 inducibility on a
heterologous promoter, only IL-3 activation of the CRE-2 reporter was
mediated via the PI3-K/Akt pathway. The SIE binding activity was
constitutively high in cells deprived of or stimulated by IL-3. In
contrast, the CRE-2 binding activity was low in cytokine-starved cells
and was strongly induced within 1 h following cytokine treatment
of cells. In addition, cytokine induction of the CRE-2 but not of the
SIE binding activity was dependent on activation of the PI3-K/Akt
signaling pathway. Lastly, we showed that CREB was one component of the
CRE-2 binding complex and played a role in IL-3 activation of the
mcl-1 reporter gene. Taken together, our results suggest
that both PI3-K/Akt-dependent and -independent pathways contribute to
the IL-3 activation of mcl-1 gene expression. Activation of
mcl-1 by the PI3-K/Akt-dependent pathway is through a
transcription factor complex containing CREB.
*
Corresponding author. Mailing address: Institute of
Molecular Biology, Academia Sinica, 128 Yen-Jiou Yuan Rd. Sec. 2, NangKang, Taipei, 11529 Taiwan, R.O.C. Phone: 886-2-2789-9228. Fax:
886-2-2782-6085. E-mail: IMBYY{at}ccvax.sinica.edu.tw.
Molecular and Cellular Biology, September 1999, p. 6195-6206, Vol. 19, No. 9
0270-7306/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
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