Alternative Splicing of the Fibronectin EIIIB Exon Depends on Specific TGCATG Repeats

ABSTRACT

The fibronectin EIIIB exon is alternatively spliced in a cell-type-specific manner, and TGCATG repeats in the intron downstream of EIIIB have been implicated in this regulation. Analysis of the intron sequence from several vertebrates shows that the pattern of repeats in the 3′ half of the intron is evolutionarily conserved. Point mutations in certain highly conserved repeats greatly reduce EIIIB inclusion, suggesting that a multicomponent complex may recognize the repeats. Expression of the SR protein SRp40, SRp20, or ASF/SF2 stimulates EIIIB inclusion. Studies of the interplay between mutations in the repeats and SRp40-stimulated inclusion suggest that the repeats are recognized in many, if not all, cell types, and that EIIIB inclusion may be regulated by quantitative changes in multiple factors.

ACKNOWLEDGMENTS

We especially thank Gene Huh and Richard Hynes for valuable discussion and for generous sharing of reagents and protocols. We thank Javier Caceres (Krainer lab) and Jin Wang (Manley lab) for gifts of SR expression plasmids; the Page lab, Carlos Semino, and Peggy Kolm for gifts of chicken and frog DNA; and John Augliera for automated sequencing. We thank Doug Black, Rebecca Taub, and Jo Yeakley for communication of unpublished results; Ben Blencowe, Gene Huh, Patrick McCaw, Joel Pomerantz, and Rock Pulak for critical reading of the manuscript; and Margarita Siafaca for secretarial support.

This work was supported by Public Health Service MERIT award R37-GM34277 and grant RO1-AI32486 from the National Institutes of Health to P.A.S. and partially by a Cancer Center Support (core) grant P30-CA14051 from the National Cancer Institute.