Abstract
Widespread anti-inflammatory actions of glucocorticoid hormones are mediated by the glucocorticoid receptor (GR), a ligand-dependent transcription factor of the nuclear receptor superfamily. In conjunction with its corepressor GR-interacting protein-1 (GRIP1), GR tethers to the DNA-bound activator protein-1 and NF-κB and represses transcription of their target proinflammatory cytokine genes. However, these target genes fall into distinct classes depending on the step of the transcription cycle that is rate-limiting for their activation: Some are controlled through RNA polymerase II (PolII) recruitment and initiation, whereas others undergo signal-induced release of paused elongation complexes into productive RNA synthesis. Whether these genes are differentially regulated by GR is unknown. Here we report that, at the initiation-controlled inflammatory genes in primary macrophages, GR inhibited LPS-induced PolII occupancy. In contrast, at the elongation-controlled genes, GR did not affect PolII recruitment or transcription initiation but promoted, in a GRIP1-dependent manner, the accumulation of the pause-inducing negative elongation factor. Consistently, GR-dependent repression of elongation-controlled genes was abolished specifically in negative elongation factor-deficient macrophages. Thus, GR:GRIP1 use distinct mechanisms to repress inflammatory genes at different stages of the transcription cycle.