Characterization of a third transforming growth factor beta 1 transcript in rat tracheal epithelial cells.
It has been previously reported (R. W. Steigerwalt et al., Mol. Carcinog., 5:32-40, 1992) that primary cultures of rat tracheal epithelial (RTE) cells and immortalized RTE cell lines produce three mRNA transcripts [2.5, 1.9, 1.4 kilobases (kb)] which hybridize to a murine transforming growth factor beta 1 (TGF-beta 1) complementary DNA probe. In this report, we show that the 1.9- and 1.4-kb transcripts are not detectable by Northern analysis of resting adult trachea but are induced in regenerating tracheal grafts and tumors formed from transformed RTE cells. Northern analysis of the TGF-beta 1 transcripts with subclones of the murine complementary DNA demonstrate that the 1.4-kb transcript lacks much of the 5' untranslated region (UTR). RNase protection analysis was used to map the transcriptional start site of the 1.4-kb transcript to within 30-40 base pairs of the first ATG codon. No differences in the coding or 3' UTR were detected between the 1.4-kb and the 2.5-kb transcripts. Although RTE cells produce a 1.9-kb TGF-beta 1 mRNA, we were unable to detect a previously reported unique 3' UTR, which we found to be almost identical to a rat mitochondrial ATPase sequence. Because the 1.4-kb transcript is missing most of the long GC-rich 5' UTR, it may be translated at a different rate than the 2.5- and 1.9-kb transcripts, or it may code for an intracellular form of TGF-beta 1. The 1.4-kb transcript has been observed under several conditions of injury or stress and, therefore, may be an important component of the TGF-beta 1 response to these conditions.
Ostrowski
L E
LE
Laboratory of Pulmonary Pathobiology, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709.
Gray
T E
TE
Randell
S H
SH
Nettesheim
P
P
D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D004847:Epithelial Cells; D004848:Epithelium / Q000737:chemistry; D008297:Male; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000032:analysis / Q000737:chemistry*; D051381:Rats; D011916:Rats, Inbred F344; D014132:Trachea / Q000737:chemistry* / Q000166:cytology; D016212:Transforming Growth Factor beta / Q000235:genetics*
D012333:RNA, Messenger; D016212:Transforming Growth Factor beta