Identification of a novel RING finger protein as a coregulator in steroid receptor-mediated gene transcription.
Using the DNA-binding domain of androgen receptor (AR) as a bait in a yeast two-hybrid screening, we have identified a small nuclear RING finger protein, termed SNURF, that interacts with AR in a hormone-dependent fashion in both yeast and mammalian cells. Physical interaction between AR and SNURF was demonstrated by coimmunoprecipitation from cell extracts and by protein-protein affinity chromatography. Rat SNURF is a highly hydrophilic protein consisting of 194 amino acid residues and comprising a consensus C3HC4 zinc finger (RING) structure in the C-terminal region and a bipartite nuclear localization signal near the N terminus. Immunohistochemical experiments indicated that SNURF is a nuclear protein. SNURF mRNA is expressed in a variety of human and rat tissues. Overexpression of SNURF in cultured mammalian cells enhanced not only androgen, glucocorticoid, and progesterone receptor-dependent transactivation but also basal transcription from steroid-regulated promoters. Mutation of two of the potential Zn2+ coordinating cysteines to serines in the RING finger completely abolished the ability of SNURF to enhance basal transcription, whereas its ability to activate steroid receptor-dependent transcription was maintained, suggesting that there are separate domains in SNURF that mediate interactions with different regulatory factors. SNURF is capable of interacting in vitro with the TATA-binding protein, and the RING finger domain is needed for this interaction. Collectively, we have identified and characterized a ubiquitously expressed RING finger protein, SNURF, that may function as a bridging factor and regulate steroid receptor-dependent transcription by a mechanism different from those of previously identified coactivator or integrator proteins.
Moilanen
A M
AM
Department of Physiology, Institute of Biomedicine, University of Helsinki, FIN-00014 Helsinki, Finland.
Poukka
H
H
Karvonen
U
U
Häkli
M
M
Jänne
O A
OA
Palvimo
J J
JJ
D000595:Amino Acid Sequence; D000818:Animals; D016466:CHO Cells; D019556:COS Cells; D002460:Cell Line; D003001:Cloning, Molecular; D006224:Cricetinae; D005786:Gene Expression Regulation; D015723:Gene Library; D006367:HeLa Cells; D006801:Humans; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D051381:Rats; D011944:Receptors, Androgen / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000378:metabolism; D016385:TATA Box; D013737:Testis / Q000378:metabolism; D014157:Transcription Factors / Q000096:biosynthesis / Q000737:chemistry / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection; D044767:Ubiquitin-Protein Ligases; D016335:Zinc Fingers
D009687:Nuclear Proteins; C114070:RNF4 protein, human; D011944:Receptors, Androgen; D011993:Recombinant Fusion Proteins; D014157:Transcription Factors; C486410:Rnf4 protein, mouse; C486411:Rnf4 protein, rat; D044767:Ubiquitin-Protein Ligases