A bovine homolog to the human myogenic determination factor myf-5: sequence conservation and 3' processing of transcripts.

A bovine cDNA library from fetal skeletal muscle myoblasts. was screened with a 274 bp probe to a conserved region of the mouse MyoD1 cDNA. One positive recombinant, designated bmyf, was found to contain a 1931 bp insert with an open reading frame encoding a predicted protein highly related to the human myogenic factor myf-5 Human and bovine factors are 96% homologous in their predicted amino acid sequences. At the nucleotide level, bmyf and myf-5 are 92% identical in the coding region and 74 and 80% homologous in their 5'- and 3'-untranslated regions, respectively. The bmyf cDNA, nevertheless, extends 475 nucleotides beyond a polyadenylation signal common to both cDNAs. Bmyf transcripts are expressed exclusively in skeletal muscle where three transcripts of 1.5, 2 and 3 kb were detected. While the 1.5 kb transcript lacks sequences 3' to the polyadenylation signal at nt 1415 in the bmyf cDNA, both the 2 and 3 kb RNAs contain these sequences suggesting that bmyf transcripts are alternatively polyadenylated. Bmyf cDNA can activate the expression of the myogenic program in C3H10T1/2 fibroblasts as assayed by stable and transient transfection experiments.