Abstract
Recently, we have cloned a general coactivator named coactivator activator (CoAA). It contains RNA-recognition motifs (RRMs). Further, CoAA interacts with DNA-dependent protein kinase (DNA-PK) that may associate with basal transcriptional machinery. Thus, we hypothesized that CoAA may locate the RNA polymerase II (Pol II)-containing basal transcriptional machinery. We investigated the interaction between CoAA and RNA using monoribopolymer interacting assay, which showed that RRM of CoAA bound with RNA directly. Steroid receptor RNA activator (SRA) has been cloned and characterized as a RNA-form coactivator. Using transient transfection-based reporter assay, CoAA showed a synergistic activation with SRA on glucocorticoid receptor (GR)-, estrogen receptor (ERα)-, and thyroid hormone receptor (TRβ1)-mediated transcription. RRM was not required on SRA action. Thus, we tested if SRA affects the ligand-binding domain (LBD) of TR in the presence of CoAA using mammalian one-hybrid assay. Transcription was activated when Gal4-fused TRβ1-LBD was cotranscfected with CoAA and SRA into CV-1 cells. SRA synergistically activated transcription with CoAA. Suggesting that SRA may contribute to the LBD-mediated transcriptional activation in the presence of CoAA. We concluded that intrinsic CoAA may located the Pol II-containing basal transcriptional machinery, and may associate with newly produced RNA. Also CoAA interacts with SRA-containing HAT complex. Taken together, CoAA could interact both newly produced RNA and SRA. [Jpn J Physiol 54 Suppl:S221 (2004)]
