A network of steroid receptor transcription factors regulates ovarian chromatin remodelling in the transition to ovulation

Steroid receptors are transcription factors activated by progesterone (PGR), androgen (AR) and glucocorticoid (GR) that bind the same canonical DNA sequence to modulate genome function in response to steroid hormones. However, the mechanisms defining unique physiological roles of these conserved receptors within the same tissue context, including the ovary, remains elusive. We describe the dynamic association between each steroid receptor cistrome in the mouse ovary responding to the hormonal switch from follicle development to ovulation, and generate chromatin conformation maps to define steroid receptor roles in promoter-enhancer interactions and gene transcription. Ovulatory hormones trigger PGR and GR binding to novel chromatin sites, promoting transcriptional activation of genes that are required for ovulation, whereas AR-chromatin interactions and AR-associated genes are repressed. Integration of genomic and transcriptomic data illustrates two parallel modes of PGR-mediated gene activation. Unique cooperation between PGR and GR enables their recruitment to previously inaccessible promoters, increasing histone acetylation, chromatin accessibility and transcription activation, with PGR being the indispensable component of this transcriptional complex. Alternatively, PGR tethered to enhancers interacts with preaccessible, AR/GR-bound promoters induces gene activation. Our findings illustrate the multifaceted steroid receptor interactions that translate progressive change in steroid environments to collectively reprogram granulosa cell genome function to switch from follicle development to ovulation.