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Mol Cell Biol, April 1998, p. 2205-2217, Vol. 18, No. 4
Department of Pharmacology and Cancer
Biology,1
Division of
Nephrology,2
Department of
Medicine,3 and
Department of
Microbiology,5 Duke University Medical Center,
Durham, North Carolina, and
Department of Biochemistry and
Biophysics, Center for Cancer Biology and Nutrition, Albert B. Alkek Institute of Biological Sciences and Technology, Texas A&M
University, Houston, Texas4
Received 17 October 1997/Returned for modification 11 December
1997/Accepted 22 January 1998
Alternative splicing of fibroblast growth factor receptor 2 (FGF-R2) is an example of highly regulated alternative splicing in
which exons IIIb and IIIc are utilized in a mutually exclusive manner
in different cell types. The importance of this splicing choice is
highlighted by studies which indicate that deregulation of the FGF-R2
splicing is associated with progression of prostate cancer. Loss of
expression of a IIIb exon-containing isoform of FGF-R2 [FGF-R2
(IIIb)] accompanies the transition of a well-differentiated, androgen-dependent rat prostate cancer cell line, DT3, to the more
aggressive, androgen-independent AT3 cell line. We have used transfection of rat FGF-R2 minigenes into DT3 and AT3 cancer cell lines
to study the mechanisms that control alternative splicing of rat
FGF-R2. Our results support a model in which an important cis-acting element located in the intron between these
alternative exons mediates activation of splicing using the upstream
IIIb exon and repression of the downstream IIIc exon in DT3 cells. This
element consists of 57 nucleotides (nt) beginning 917 nt downstream of
the IIIb exon. Analysis of mutants further demonstrates that an 18-nt
"core sequence" within this element is most crucial for its
function. Based on our observations, we have termed this sequence
element ISAR (for intronic splicing activator and repressor), and we
suggest that factors which bind this sequence are required for
maintenance of expression of the FGF-R2 (IIIb) isoform.
0270-7306/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
An Intronic Sequence Element Mediates Both
Activation and Repression of Rat Fibroblast Growth Factor Receptor
2 Pre-mRNA Splicing
*
Corresponding author. Mailing address: Department of
Pharmacology and Cancer Biology, Box 3686, Duke University Medical
Center, Durham, NC 27710. Phone: (919) 613-8632. Fax: (919) 613-8646. E-mail: garci001{at}mc.duke.edu.
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