title: Characterization of a strong repression domain in the hinge region of orphan nuclear receptor hB1F/hLRH-1.
abstract: Human hepatitis B virus enhancer II B1 binding factor (hB1F  also known as NR5A2, LRH-1, FTF or CPF) is an orphan nuclear receptor and belongs to the fushi tarazu factor I (FTZ-F1) subfamily. It plays important roles in the transcriptional regulation of a number of genes involved in bile acid biosynthesis pathway, hepatitis B virus (HBV) replication and liver specific regulatory network. Like other nuclear receptors, hB1F is composed of modular functional domains. We characterized a domain in its hinge region that imposes a strong repression on the transcriptional activity of hB1F, which is important for the function of hB1F on regulating the activity of HBV enhancer II/core promoter. Mutations of the core residues in this domain abrogate the repression. Bioinformatic analysis reveals that the amino acid sequence of this region is highly conserved only among members of the FTZ-F1 subfamily. The repression is observed in five cell lines tested, while the degree of the repression varies greatly, which does not parallel with the expression level of the DEAD box protein of 130 kD (DP103), a potential interacting protein of a homologous domain in the steroidogenic factor 1 (SF-1). Moreover, the repression is not affected by the silencing mediator for retinoic acid receptor and thyroid hormone receptor (SMRT) and steroid receptor coactivator 1 (SRC-1). Collectively, these data suggest a novel regulatory mechanism for the transcriptional activity of hB1F.
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D015153:Blotting, Western; D019556:COS Cells; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D019295:Computational Biology / Q000379:methods; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation / Q000235:genetics; D006367:HeLa Cells; D051548:Histone Acetyltransferases; D006801:Humans; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D056985:Nuclear Receptor Co-Repressor 2; D056920:Nuclear Receptor Coactivator 1; D017354:Point Mutation; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D054339:Steroidogenic Factor 1; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; C539130:NCOR2 protein, human; C515057:NR5A1 protein, human; C082631:NR5A2 protein, human; C539131:Ncor2 protein, mouse; C431936:Nr5a2 protein, mouse; D056985:Nuclear Receptor Co-Repressor 2; D018160:Receptors, Cytoplasmic and Nuclear; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D054339:Steroidogenic Factor 1; D015534:Trans-Activators; D014157:Transcription Factors; C515058:steroidogenic factor 1, mouse; D008156:Luciferases; D051548:Histone Acetyltransferases; C538859:NCOA1 protein, human; C538861:Ncoa1 protein, mouse; D056920:Nuclear Receptor Coactivator 1