A Steroid Receptor Coactivator, SRA, Functions as an RNA and is Present in an SRC-1 Complex.
Nuclear receptors play critical roles in the regulation of eukaryotic gene expression.
SRA is selective for steroid hormone receptors and mediates transactivation via their amino-terminal activation function. Biochemical fractionation shows that SRA exists in distinct ribonucleoprotein complexes, one of which contains the nuclear receptor coactivator steroid receptor coactivator 1. We suggest that SRA may act to confer functional specificity upon multiprotein complexes recruited by liganded receptors during transcriptional activation. SRA is different from other known coregulators in that it functions as an endogenous RNA transcript. We have described the isolation of three SRA isoforms deduced from sequencing of different cDNAs and genomic clones from different species.