Positive regulation of connexin32 transcription by hepatocyte nuclear factor-1alpha.
Connexin32 (Cx32) encodes the predominant gap junction protein expressed by hepatocytes. We investigated the transcriptional control of Cx32 in expressing and nonexpressing rat liver cell lines and hypothesized that a putative hepatocyte nuclear factor-1 (HNF-1) binding site (centered at mp -187) in the liver-active, P1 promoter is essential for transcription of Cx32. HNF-1alpha was expressed by Cx32-expressing rat liver cell lines and bound the promoter at the -187 site, but was not expressed by non-Cx32-expressing hepatic lines. Stable transfection of non-Cx32-expressing WB-F344 rat liver epithelial cells with HNF-1alpha stimulated a transfected Cx32 promoter element (mp -244 to -33), binding of HNF-1alpha to the -187 site, and expression of endogenous Cx32. Site-directed mutagenesis of this HNF-1 binding site abolished HNF-1alpha binding and proximal promoter activity. Hepatic Cx32 expression was also significantly decreased in HNF-1alpha(-/-) mice. These data indicate that HNF-1alpha is a positive regulator of Cx32 expression in hepatic cells.
Koffler
Lucas D
LD
Department of Pathology, Medical College of Ohio, 3055 Arlington Avenue, Toledo, OH 43614, USA.
Fernstrom
Martha J
MJ
Akiyama
Taro E
TE
Gonzalez
Frank J
FJ
Ruch
Randall J
RJ
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D017630:Connexins / Q000096:biosynthesis / Q000235:genetics*; D004268:DNA-Binding Proteins; D051537:Hepatocyte Nuclear Factor 1; D051538:Hepatocyte Nuclear Factor 1-alpha; D051539:Hepatocyte Nuclear Factor 1-beta; D008099:Liver / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D009687:Nuclear Proteins; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D011916:Rats, Inbred F344; D020218:Response Elements; D014157:Transcription Factors / Q000235:genetics / Q000502:physiology*; D015533:Transcriptional Activation; D014162:Transfection; D000097002:Gap Junction beta-1 Protein
D017630:Connexins; D004268:DNA-Binding Proteins; D051537:Hepatocyte Nuclear Factor 1; D051538:Hepatocyte Nuclear Factor 1-alpha; D051539:Hepatocyte Nuclear Factor 1-beta; D009687:Nuclear Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; D000097002:Gap Junction beta-1 Protein; C496488:Hnf1a protein, mouse; C496489:Hnf1a protein, rat; C496496:Hnf1b protein, mouse