Isolation of Genomic Sequence Encoding a Biologically Active Bovine TGF- α Protein

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Abstract
Genomic clones encoding bovine TGF-α were identified by hybridization with probes derived from human TGF-α sequence. Nucleotide sequence of the clones predicts that mature bovine TGF-α is a 50 amino acid polypeptide which shares 96% and 92% homology with human and rat TGF-α, respectively. Bovine TGF-α with the predicted sequence was chemically synthesized and tested for activity. Synthetic bovine TGF-α competes in a radioreceptor assay with labelled mouse EGF with activity parallel to that of human TGF-α and mouse EGF. The mitogenic activity of bovine TGF-α is comparable to that of human EGF in causing proliferation of bovine mammary epithelial cells. An ∼ 5.0 kilobase RNA transcript is observed in polyadenylated RNA from MDBK cells by Northern blot analysis. The polymerase chain reaction detects the presence of a TGF-α transcript in many bovine tissues. These data indicate that bovine TGF-α may be a normal regulator of cell growth in the bovine animal.