Identification of the start sites for the 1.9- and 1.4-kb rat transforming growth factor-beta1 transcripts and their effect on translational efficiency.
Three distinct transforming growth factor-beta1 (TGF-beta1) transcripts of 2.5, 1.9 and 1.4kb have been described, but the start sites and functional significance of the shorter transcripts are unknown. Here, we have cloned and sequenced a rat genomic fragment encoding approximately 1250 bases upstream of the start of the TGF-beta1 open reading frame. Using a combination of ribonuclease protection and 5' RACE-PCR analysis, we have mapped the start sites for the two shorter TGF-beta1 transcripts in NRP152 cells, a rat prostatic epithelial cell line that expresses all three transcripts at high levels. The 1.4-kb mRNA starts 25 bases upstream of the initiator AUG, whereas the 1.9-kb mRNA has two start sites 366 and 401 bases upstream of the AUG. Polysome analysis of the NRP152 cells indicates that the 1.9-kb transcript is very efficiently translated, whereas the 2.5- and 1.4-kb transcripts appear to be poorly translated. Differential regulation of TGF-beta1 transcript size may therefore represent an important mechanism for regulating TGF-beta1 protein levels.
Laboratory of Cell Regulation and Carcinogenesis, National Cancer Institute, Bethesda, MD 20892, USA.
Y
Y
Yang
M
M
Mumy
D
D
Romeo
L M
LM
Wakefield
D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D003001:Cloning, Molecular; D003062:Codon; D004847:Epithelial Cells / Q000378:metabolism; D006801:Humans; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D016133:Polymerase Chain Reaction; D011132:Polyribosomes / Q000378:metabolism; D011467:Prostate / Q000378:metabolism; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D051381:Rats / Q000235:genetics*; D011994:Recombinant Proteins / Q000096:biosynthesis; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D014158:Transcription, Genetic; D016212:Transforming Growth Factor beta / Q000096:biosynthesis / Q000235:genetics*
D003062:Codon; D012333:RNA, Messenger; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta