Genomic structure of the chicken slow skeletal muscle troponin T gene.

Troponin T (TnT) is a key protein for Ca(2+)-sensitive molecular switching of muscle contraction. In vertebrates, three TnT genes have been identified, which produce isoforms characteristic of cardiac, fast skeletal, and slow skeletal muscles through alternative splicing in a tissue-specific and developmentally regulated manner. The diversification of myofibers into forms with specific metabolic and contractile characteristics is thought to be closely associated with the differential expression of these TnT isoforms. Herein, we determined the nucleotide sequence of the chicken slow skeletal muscle TnT gene and its upstream region. The gene was simpler in structure than the two other chicken genes. The transcription initiation site was positioned 183 bp upstream of the 3' end of exon 1. Alternative splicing of exon 5 using an internal acceptor site generated two distinct slow skeletal muscle troponin T (sTnT) transcripts. We identified possible regulatory elements, M-CAT-like, CACC-box, and E-box (E-box1 to E-box3) motifs in the upstream region and an E-box motif (E-box4) in exon 1.