Characterization of the functional domains and quantification in the cells of a steroid receptor-binding protein, SRB-RGS
We isolated the cDNA of a steroid receptor-binding protein, SRB-RGS, binding to the estrogen receptor (ER)α. SRB-RGS very efficiently suppressed the ERs-mediated transcriptional activities. SRB-RGS interacted with ER on DNA. SRB-RGS was localized in both the nucleus and cytoplasm in the cells. SRB-RGS induced cell death of HeLa cells. In the present paper, we examined the functional domains of SRB-RGS. The effects of SRB-RGS on the ERs-mediated transcriptional activities were exerted by the PDZ domain-containing region and/or the RGS domain-containing region of SRB-RGS. The nuclear localization signal (NLS) was in the RGS domain containing one basic region. Either the PDZ or RGS domains on SRBRGS induced cell death. Either the PDZ or RGS domains on SRB-RGS were necessary for transcriptional suppression, subcellular localization and induction of the death in HeLa cells. The expression of SRB-RGS was observed in the cytoplasm or both the cytoplasm and nucleus of various types of cells by confocal laser-scanning microscopy after immunostaining of the cells. SRB-RGS was expressed in all types of cells examined by using real-time RT-PCR. (Accepted on March , 28, 2011)
