The chicken fast skeletal troponin I gene: exon organization and sequence

Abstract

The gene encoding the fast skeletal isoform of the chick troponin I (sTnI) protein has been sequenced and its organization into exons and introns established. The gene is approximately 4.5 kb in length and composed of 8 exons, the first of which contains solely 5' untranslated sequence. In addition to its major mRNA product, there is evidence that the sTnI gene encodes a second mRNA, present at low abundance levels in embryonic skeletal muscle. Sl nuclease protection and primer extension experiments indicate that the low abundance mRNA is initiated approximately 47 nucleotides upstream of the major transcriptional initiation site. Both mRNAs appear to encode identical sTnI polypeptides. A comparison of nucleotide sequence in the 5' flanking region of several muscle-specific genes, including the sTnI gene, reveals a heptanucleotide consensus sequence, 5'-CATTCCT-3', which is conserved in the 5' flanking regions of many vertebrate contractile protein genes.

Regulation of the rat cardiac troponin I gene by the transcription factor GATA-4

“…In contrast with the avian fast skeletal-muscle TnI gene and the human slow skeletal-muscle TnI gene, the first exon of the cardiac TnI gene contains the start codon. The avian fast skeletal-muscle, rat and human slow skeletal-muscle TnI genes, like several other muscle-specific genes, have a first exon that is untranslated [12,13,27,28]. The intron-exon structure of the avian fast skeletal-muscle, the human slow skeletal-muscle and rat and mouse cardiac genes are completely conserved for exons 5, 6 and 7, which encode the majority of the protein sequence [13,29].…”

Developmental expression of troponin I isoforms in fetal human heart

“…Multiple isoforms of each of these proteins exist and are expressed in a tissuespecific and developmentally regulated manner. For -troponin I, three principal isoforms have been described on the basis of protein sequencing [1,2], antibody studies [3][4][5][6][7] and, more recently, by molecular cloning [8][9][10][11][12][13]. These isoforms are associated' with fast skeletal muscle, slow skeletal muscle or cardiac muscle, and are referred to here as fast Tnl (Tnlf), slow Tnl (Tnls) and cardiac TnI (Tnlc), respectively.…”

Muscle-specific activity of the skeletal troponin I promoter requires interaction between upstream regulatory sequences and elements contained within the first transcribed exon.

“…A second conserved, variable sequence motif, dubbed MEF-1, has been shown to be an essential component of the muscle-specific enhancer of the creatine kinase gene (7) and may be an essential component of the enhancers of other muscle-specific genes (11,58). Finally, a motif with the consensus 5'-CATTCCT-3' (M-CAT motif) is protein genes (44) and is required for the expression of the cardiac troponin T gene in embryonic skeletal muscle cells (35; J. H. Mar and C. P. Ordahl, Mol. Cell.…”

“…Thus, our results show that, for the sTnI gene, musclespecific expression is governed by a complex interaction between multiple elements located both in the promoter and in the intragenic regions. (44) by partial digestion at an AvaI site located at position +61 (all nucleotide positions are relative to the transcription initiation site) and complete digestion at an EcoRI site at position -1000 in the 5'-flanking sequence ( Fig. 1A and B).…”

“…The organization of the chicken sTnI gene (Fig. 1A) has been determined by analysis of its nucleotide sequence (44). The region immediately upstream from the transcription initiation site has nominal TATA and CCAAT motifs (Fig.…”