Transforming growth factor-beta1 up-regulation of human alpha(1)(I) collagen is mediated by Sp1 and Smad2 transacting factors.
Hepatic fibrosis results from excessive deposition of type I collagen. The roles of Smads in mediating the effect of transforming growth factor-beta1 (TGFbeta1) on activation of the alpha(1)(I) collagen promoter were determined. Smads bind in association with Sp1 to the CC(GG)-rich TGFbeta1 responsive element of the promoter that lacks the classical Smad recognition element, and enhance binding of Sp1. In transfection experiments, TGFbeta1 activated a proximal promoter, but not promoters mutated at sites that prevented Sp1 binding. Sp1 alone or the combination of Smad2 and Smad4 activated the promoter in transfected human LX-2 stellate cells. Sp1 or Smad2 knockdowns with siRNAs prevented the effect of TGFbeta1 in enhancing the promoter. In conclusion, this study shows that Smads bind in association with Sp1 to the CC(GG)-rich TGFbeta1 responsive element of the human alpha(1)(I) collagen promoter that lacks the classical Smad recognition element, thus enhancing the binding of Sp1 and in this manner activating the collagen promoter.
Sysa
Polina
P
Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205-2195, USA.
Potter
James J
JJ
Liu
Xiaopu
X
Mezey
Esteban
E
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D015153:Blotting, Western; D002460:Cell Line; D047369:Chromatin Immunoprecipitation; D024042:Collagen Type I / Q000235:genetics*; D000090602:Collagen Type I, alpha 1 Chain; D024202:Electrophoretic Mobility Shift Assay; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D055166:Hepatic Stellate Cells / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D009154:Mutation; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D034741:RNA, Small Interfering / Q000235:genetics; D051899:Smad2 Protein / Q000235:genetics / Q000378:metabolism*; D051900:Smad3 Protein / Q000235:genetics / Q000378:metabolism; D051901:Smad4 Protein / Q000235:genetics / Q000378:metabolism; D016329:Sp1 Transcription Factor / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology*; D015854:Up-Regulation / Q000187:drug effects
D024042:Collagen Type I; D000090602:Collagen Type I, alpha 1 Chain; D034741:RNA, Small Interfering; D051899:Smad2 Protein; D051900:Smad3 Protein; D051901:Smad4 Protein; D016329:Sp1 Transcription Factor; D053773:Transforming Growth Factor beta1