Regulation of alternatively spliced alpha-tropomyosin gene expression by nerve extract.

Muscle cells were incubated with extracts prepared from neural tissue to investigate the mechanisms and factors which regulate mRNA transcript production of the alternatively spliced alpha-tropomyosin (alpha-TM) gene. Results from RNA analyses demonstrate that alpha-TM transcripts are dramatically altered by decreasing the production of the striated specific isoform while concomitantly increasing a cytoplasmic isoform. The factors which regulate alpha-TM expression are derived from neural tissue and act at the post-transcriptional level through a trans-activation mechanism. Furthermore, these factors can also alter the expression of alpha-TM mRNA isoforms in both non-muscle and primary muscle cells by regulating the exon splice site selection determined by endogenous trans-acting factors and force the production of a specific cytoplasmic isoform. The results demonstrate that the neural factors which regulate alpha-TM expression act through mechanisms and processes which are common to many different cell types and cell lineages.