Identification and molecular characterization of cellular factors required for glucocorticoid receptor-mediated mRNA decay

Glucocorticoid (GC) receptor (GR) has been shown recently to bind a subset of mRNAs and elicit rapid mRNA degradation. However, the molecular details of GR-mediated mRNA decay (GMD) remain unclear. Here, we demonstrate thatGMDtriggers rapid degradation of targetmRNAsin a translation-independent and exon junction complexindependent manner, confirming that GMD is mechanistically distinct from nonsense-mediated mRNA decay (NMD). Efficient GMD requires PNRC2 (proline-rich nuclear receptor coregulatory protein 2) binding, helicase ability, and ATM-mediated phosphorylation of UPF1 (upstream frameshift 1). We also identify two GMD-specific factors: an RNA-binding protein,YBX1(Y-box-binding protein 1), and an endoribonuclease,HRSP12(heat-responsive protein 12). In particular, using HRSP12 variants, which are known to disrupt trimerization of HRSP12, weshowthat HRSP12 plays an essential role in the formation of a functionally activeGMDcomplex. Moreover, we determine the hierarchical recruitment of GMD factors to target mRNAs. Finally, our genome-wide analysis shows that GMD targets a variety of transcripts, implicating roles in a wide range of cellular processes, including immune responses.