Transcriptional repression of an embryo-specific muscle gene.

Skeletal muscle involves both the induction and repression of gene expression. Although activation and up-regulation of several contractile protein genes has been shown to occur via transcriptional mechanisms, the mechanisms by which contractile protein genes are repressed during muscle development remain unknown. However, a post-transcriptional mechanism has been implicated in the repression of thymidine kinase expression during muscle development. The chicken cardiac troponin T (cTNT) gene is expressed in early embryonic skeletal muscle but is abruptly repressed in late embryonic/fetal development. Using run-on transcription assays we demonstrate here that cTNT gene repression occurs at the level of transcription. Thus, transcriptional as well as post-transcriptional mechanisms operate both to activate and repress gene expression during skeletal muscle development.