Transforming Growth Factor-β2: Cdna Cloning and Sequence Analysis

We have obtained a cDNA clone coding for human transforming growth factor (TGF)-β2. The clone was isolated from a tamoxifen-treated human prostatic adenocarcinoma cell line (PC-3) using oligonucleotide probes based on the partial amino acid sequence of purified TGF-β2. The cDNA sequence predicts that TGF-β2 is synthesized as a 442-amino-acid polypeptide precursor from which the mature 112-amino-acid TGF-β2 subunit is derived by proteolytic cleavage. The proteins coded for by the human TGF-β1 and TGF-β2 cDNAs show an overall homology of 41%. The mature and amino-terminal precursor regions show 71% and 31% homology, respectively. Northern blot analysis identified TGF-β2 transcripts of 4.1, 5.1, and 6.5 kb using mRNA from several different sources. Analysis of polyadenylated RNA from tamoxifen-treated PC-3 cells showed that these cells contain higher numbers of transcripts for TGF-β1 than for TGF-β2, although they produce more TGF-β2 protein than TGF-β1. This suggests that there is a post-transcriptional level of regulation for the production of these proteins.