cis-elements involved in alternative splicing in the rat beta-tropomyosin gene: the 3'-splice site of the skeletal muscle exon 7 is the major site of blockage in nonmuscle cells.
We have been using the rat beta-tropomyosin (beta-TM) gene as a model system to study the mechanism of alternative splicing. The beta-TM gene spans 10 kb with 11 exons and encodes two distinct isoforms, namely skeletal muscle beta-TM and fibroblast TM-1. Exons 1-5, 8, and 9 are common to all mRNAs expressed from this gene. Exons 6 and 11 are used in fibroblasts, as well as in smooth muscle cells, whereas exons 7 and 10 are used exclusively in skeletal muscle cells. Our previous studies localized the critical elements for regulated alternative splicing to sequences within exon 7 and the adjacent upstream intron. We also demonstrated that these sequences function, in part, to regulate splice-site selection in vivo by interacting with cellular factors that block the use of the skeletal muscle exon in nonmuscle cells (1). Here we have further characterized the critical cis-acting elements involved in alternative splice site selection. Our data demonstrate that exon 7 and its flanking intron sequences are sufficient to regulate the suppression of exon 7 in nonmuscle cells when flanked by heterologous exons derived from adenovirus. We have also shown by both in vivo and in vitro assays that the blockage of exon 7 in nonmuscle cells is primarily at its 3'-splice site. A model is presented for regulated alternative splicing in both skeletal muscle and nonmuscle cells.
Guo
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Cold Spring Harbor Laboratory, NY 11724.
Helfman
D M
DM
D017398:Alternative Splicing; D000818:Animals; D001483:Base Sequence; D004247:DNA; D004591:Electrophoresis, Polyacrylamide Gel; D005091:Exons; D006367:HeLa Cells; D006801:Humans; D007438:Introns; D008969:Molecular Sequence Data; D009132:Muscles / Q000378:metabolism*; D009154:Mutation; D016133:Polymerase Chain Reaction; D051381:Rats; D014335:Tropomyosin / Q000235:genetics*
D014335:Tropomyosin; D004247:DNA