Mechanism of regulation of HGF/SF gene expression in fibroblasts by TGF-beta1.
The effect of transforming growth factor beta 1 (TGF-beta1) on levels of hepatocyte growth factor/scatter factor (HGF/SF) gene transcripts was investigated in the human lung embryonic fibroblast cell line, MRC-5. TGF-beta1 markedly reduced the expression of the 6. 0-kb and 3.0-kb HGF/SF mRNA, which encode full-length HGF/SF, but it had little effect on the expression of the alternatively spliced 1. 5-kb mRNA, which encodes NK2, a competitive HGF/SF antagonist. Using actinomycin D to block RNA synthesis, it was observed that TGF-beta1 had little effect on the stability of the 1.5-kb NK2 mRNA but increased the rate of degradation of the 6.0- and 3.0-kb HGF/SF mRNA transcripts by a mechanism that was dependent on new protein synthesis. TGF-beta1 minimally increased rather than reduced HGF/SF promoter activity in cells transiently transfected with chloramphenicol acetyltransferase (CAT) reporter genes driven by HGF/SF gene 5'-flanking sequences. In MRC-5 cells, TGF-beta1 modulates HGF/SF gene transcripts at the posttranscriptional level in order to favour expression of the 1.5-kb mRNA that encodes the truncated protein NK2.
Harrison
P
P
Institute of Liver Studies, GKT School of Medicine, King's Denmark Hill Campus, Bessemer Road, London, SE5 9PJ, United Kingdom.
Bradley
L
L
Bomford
A
A
D020413:3' Untranslated Regions; D015152:Blotting, Northern; D002460:Cell Line; D003001:Cloning, Molecular; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005347:Fibroblasts / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D017228:Hepatocyte Growth Factor / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D011401:Promoter Regions, Genetic; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011994:Recombinant Proteins / Q000378:metabolism; D012260:Ribonucleases / Q000378:metabolism; D013997:Time Factors; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D001616:beta-Galactosidase / Q000378:metabolism
D020413:3' Untranslated Regions; D011500:Protein Synthesis Inhibitors; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; D003609:Dactinomycin; D017228:Hepatocyte Growth Factor; D003513:Cycloheximide; D012260:Ribonucleases; D001616:beta-Galactosidase