"A small RNA derived from RNA coactivator SRA blocks steroid receptor signaling via inhibition of Pus1p-mediated pseudouridylation of SRA: evidence of a novel RNA binding domain in the N-terminus of steroid receptors."

Ghosh SK, Patton JR, Spanjaard RA

Published 2012-10-16 in Biochemistry volume 51 .

Pubmed ID: 22998747
DOI identifier: -

Estrogen receptors (ERs) and androgen receptors (ARs) are important targets for cancer therapy; however, the efficacy of receptor antagonists is limited, and alternative strategies are needed. Steroid receptor RNA Activator (SRA) is a long, noncoding RNA coactivator (although some protein-encoding 5' splice variants have also been reported) that requires pseudouridylation by Pus1p to stimulate steroid receptor signaling. A uridine at position 206 (U206), which is located in small hairpin structure STR5 in the conserved SRA core sequence, is a critical target for pseudouridylation. We assessed if synthetic STR5 could serve as a novel competitive inhibitor of ERalpha and AR signaling by disrupting the Pus1p-SRA-steroid receptor axis. STR5 specifically inhibited Pus1p-dependent pseudouridylation of SRA with higher efficiency than STR5 mutant U206A. We show that SRA binds to the N-terminal domain (NTD) of ERalpha and AR with high affinity despite the absence of a recognizable RNA binding motif (RBM). Finally, we show that STR5 specifically inhibits ERalpha- and AR-dependent transactivation of target genes in steroid-sensitive cancer cells, consistent with disruption of the targeted Pus1p-SRA pathway. Together, our results show that the NTD of ERalpha and AR contains a novel RBM that directly binds SRA, and that STR5 can serve as a novel class of RNA inhibitor of ERalpha and AR signaling by interfering with Pus1p-mediated SRA pseudouridylation. Targeting this unexplored receptor signaling pathway may pave the way for the development of new types of cancer therapeutics.

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Last modification of this entry: Oct. 11, 2013