In vivo identification of promoter elements and transcription factors mediating activation of hepatic HMG-CoA reductase by T3.
The promoter elements and transcription factors necessary for triiodothyronine (T3) induction of hepatic HMG-CoA reductase (HMGR) were investigated by transfecting rat livers with wild type and mutant HMGR promoter-luciferase constructs using in vivo electroporation. Mutations in the sterol response element (SRE), nuclear factor-y (NF-Y) site, and the newly identified upstream transcription factor-2 (USF-2) site essentially abolished the T3 response. Chromatin immunoprecipitation (ChIP) analysis demonstrated that T(3) treatment caused a 4-fold increase in in vivo binding of USF-2 to the HMGR promoter. Co-transfection of the wild type HMGR promoter with siRNAs to USF-2, SREBP-2, or NF-Y nearly abolished the T3 induction, as measured by promoter activity. These data provide in vivo evidence for functional roles for USF-2, SREBP-2, and NF-Y in mediating the T3-induction of hepatic HMGR transcription.
Boone
Lindsey R
LR
Department of Molecular Medicine, College of Medicine, University of South Florida, Tampa, FL, USA.
Niesen
Melissa I
MI
Jaroszeski
Mark
M
Ness
Gene C
GC
D000818:Animals; D001483:Base Sequence; D023081:CCAAT-Binding Factor / Q000378:metabolism; D006903:Hydroxymethylglutaryl CoA Reductases / Q000235:genetics*; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic / Q000187:drug effects; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D051782:Sterol Regulatory Element Binding Protein 2 / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism*; D014284:Triiodothyronine / Q000187:drug effects / Q000378:metabolism*; D051720:Upstream Stimulatory Factors / Q000378:metabolism
D023081:CCAAT-Binding Factor; D034741:RNA, Small Interfering; D051782:Sterol Regulatory Element Binding Protein 2; D014157:Transcription Factors; D051720:Upstream Stimulatory Factors; C497187:Usf2 protein, rat; D014284:Triiodothyronine; D006903:Hydroxymethylglutaryl CoA Reductases