Structure and regulation of the mouse cardiac troponin I gene.
The gene coding for mouse cardiac troponin I (TnI) has been cloned and sequenced. The cardiac TnI gene contains 8 exons and has an exon-intron organization similar to the quail fast skeletal TnI gene except for the region of exons 1-3, which is highly divergent. Comparative analysis suggests that cardiac TnI exon 1 corresponds to fast TnI exons 1 and 2 and that cardiac exon 3, which codes for most of the cardiac-specific amino-terminal extension and has no counterpart in the fast gene, evolved by exon insertion/deletion. The amino acid sequence of cardiac TnI exon 4 shows limited homology (36% identity) with fast TnI exon 4 but is remarkably similar (79% identity) to the corresponding sequence of slow TnI, possibly reflecting an isoform-specific TnC-binding site. The cardiac TnI gene is one of the very few contractile protein genes expressed exclusively in cardiac muscle. To identify the regulatory sequences responsible for the cardiac-specific expression of this gene we transfected cultured cardiac and skeletal muscle cells with fragments up to 4.0 kilobases of the 5'-flanking region linked to a reporter gene. Deletion analysis reveals four major regions in the 5'-flanking sequence, a minimal promoter region, which directs expression at low level in cardiac and skeletal muscle cells, and two upstream cardiac-specific positive regions separated by a negative region.
Ausoni
S
S
Department of Biomedical Sciences, University of Padova, Italy.
Campione
M
M
Picard
A
A
Moretti
P
P
Vitadello
M
M
De Nardi
C
C
Schiaffino
S
S
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D004247:DNA; D005091:Exons; D005786:Gene Expression Regulation; D051379:Mice; D008969:Molecular Sequence Data; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D011784:Quail; D051381:Rats; D012045:Regulatory Sequences, Nucleic Acid; D017386:Sequence Homology, Amino Acid; D014336:Troponin / Q000235:genetics*; D019210:Troponin I
D014336:Troponin; D019210:Troponin I; D004247:DNA