The gene encoding fibrinogen-beta is a target for retinoic acid receptor-related orphan receptor alpha.
Fibrinogen is a plasma protein synthesized by the liver. It is composed of three chains (alpha, beta, gamma). In addition to its main function as a coagulation factor, this acute phase protein is also a risk marker for atherosclerosis. Retinoic acid receptor-related orphan receptor (ROR)alpha is a nuclear receptor modulating physiopathological processes such as cerebellar ataxia, inflammation, atherosclerosis, and angiogenesis. In this study, we identified RORalpha as a regulator of fibrinogen-beta gene expression in human hepatoma cells and in mouse liver. A putative RORalpha response element (RORE) was identified in the human fibrinogen-beta promoter. EMSA showed that RORalpha binds specifically to this RORE, and cotransfection experiments in HepG2 hepatoma cells indicated that this RORE confers RORalpha-dependent transcriptional activation to both the human fibrinogen-beta and the thymidine kinase promoters. Stable transfection experiments in HepG2 and Hep3B hepatoma cells demonstrated that overexpression of RORalpha specifically increases endogenous fibrinogen-beta mRNA levels. Chromatin immunoprecipitation experiments revealed that the fibrinogen-beta RORE is occupied by RORalpha in HepG2 cells. Thus, the human fibrinogen-beta gene is a direct target for RORalpha. Furthermore, fibrinogen-beta mRNA levels in liver and plasma fibrinogen concentrations are specifically decreased in staggerer mice, which are homozygous for a deletion invalidating the Rora gene. Taken together, these data add further evidence for an important role of RORalpha in the control of liver gene expression with potential pathophysiological consequences on coagulation and cardiovascular risk.
Chauvet
Caroline
C
Centre National de la Recherche Scientifique UPR9078, Faculté de Médecine René Descartes Paris 5, site Necker, 75015 Paris, France.
Bois-Joyeux
Brigitte
B
Fontaine
Coralie
C
Gervois
Philippe
P
Bernard
Marguerite-Anne
MA
Staels
Bart
B
Danan
Jean-Louis
JL
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D002460:Cell Line; D004247:DNA / Q000235:genetics / Q000378:metabolism; D005340:Fibrinogen / Q000235:genetics*; D017930:Genes, Reporter; D006801:Humans; D066298:In Vitro Techniques; D008099:Liver / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008818:Mice, Neurologic Mutants; D057094:Nuclear Receptor Subfamily 1, Group F, Member 1; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D014162:Transfection
D057094:Nuclear Receptor Subfamily 1, Group F, Member 1; D012333:RNA, Messenger; C539738:RORA protein, human; D018160:Receptors, Cytoplasmic and Nuclear; D011994:Recombinant Proteins; C539739:Rora protein, mouse; D015534:Trans-Activators; D005340:Fibrinogen; D004247:DNA