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Molecular and Cellular Biology, February 2009, p. 871-880, Vol. 29, No. 3
0270-7306/09/$08.00+0     doi:10.1128/MCB.01709-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

SRp20 and CUG-BP1 Modulate Insulin Receptor Exon 11 Alternative Splicing{triangledown}

Supriya Sen,{dagger} Indrani Talukdar,{dagger} and Nicholas J. G. Webster*

VA San Diego Healthcare System, 3350 La Jolla Village Drive, San Diego, California 92161, and Department of Medicine and Biomedical Sciences Graduate Program, University of California, San Diego, La Jolla, California 92093

Received 5 November 2008/ Accepted 21 November 2008

The insulin receptor (IR) exists as two isoforms, IR-A and IR-B, which result from alternative splicing of exon 11 in the primary transcript. This alternative splicing is cell specific, and the relative proportions of exon 11 isoforms also vary during development, aging, and different disease states. We have previously demonstrated that both intron 10 and exon 11 contain regulatory sequences that affect IR splicing both positively and negatively. In this study, we sought to define the precise sequence elements within exon 11 that control exon recognition and cellular factors that recognize these elements. Using minigenes carrying linker-scanning mutations within exon 11, we detected both exonic splicing enhancer and exonic splicing silencer elements. We identified binding of SRp20 and SF2/ASF to the exonic enhancers and CUG-BP1 to the exonic silencer by RNA affinity chromatography. Overexpression and knockdown studies with hepatoma and embryonic kidney cells demonstrated that SRp20 and SF2/ASF increase exon inclusion but that CUG-BP1 causes exon skipping. We found that CUG-BP1 also binds to an additional intronic splicing silencer, located at the 3' end of intron 10, to promote exon 11 skipping. Thus, we propose that SRp20, SF2/ASF, and CUG-BP1 act antagonistically to regulate IR alternative splicing in vivo and that the relative ratios of SRp20 and SF2/ASF to CUG-BP1 in different cells determine the degree of exon inclusion.

* Corresponding author. Mailing address: Stein Clinical Research, Bldg. 201, Department of Medicine, 0673, University of California—San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0673. Phone: (858) 534-6275. Fax: (858) 534-6653. E-mail: nwebster{at}ucsd.edu

{triangledown} Published ahead of print on 1 December 2008.

{dagger} Both authors contributed equally to this work.

Molecular and Cellular Biology, February 2009, p. 871-880, Vol. 29, No. 3
0270-7306/09/$08.00+0     doi:10.1128/MCB.01709-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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