Nucleotide sequence of the chicken cardiac alpha actin gene: absence of strong homologies in the promoter and 3'-untranslated regions with the skeletal alpha actin sequence

Abstract

The entire nucleotide sequence of the chicken cardiac α-actin (CCαA) gene has been determined. This is the first complete sequence of a cardiac actin gene that includes the promoter region, cap site, all the introns, and the polyadenylation site. The gene contains six introns, five of which interrupt the coding region at amino acids (aa) 41, 150, 204, 267, and 327. The. first intron is in the 5'-noncoding region and is 438 bp in length. The CCαA gene encodes an mRNA of approx. 1400 bp with 5'- and 3'-untranslated region of 59 and 184 nucleotides (nt), respectively. Like the chicken skeletal α-actin gene, the CCαA gene has the codon for the aa cysteine between the initiator ATG and the codon for the N-terminal aspartic acid residue of the mature protein. There are no strong homologies (less than 13 consecutive nt) in the promoter or 3'-untranslated regions between the CCαA and chicken skeletal α-actin genes even though both are expressed in skeletal muscle during development. However, the 3'-untranslated region of the CCαA gene demonstrates significant sequence homology (76% over a 200-nt region) with the same region in the partial sequence of the human cardiac gene. The conservation of these sequence homologies between identical isoforms rather than the different α actin genes suggests these conserved regions may have a role in regulation rather than tissue-specific expression, as previously proposed.