Androgens Regulate Ovarian Gene Expression Through Modulation of Ezh2 Expression and Activity
A substantial amount of evidence suggests that androgen signaling through classical androgen receptors is critical for both normal and pathologic ovarian physiology. Specifically, we and others have shown that, in mouse granulosa cells, androgen actions through both extranuclear and nuclear androgen receptor signaling are critical for normal follicle development and ovulation. Here, we show that androgens through the PI3K/Akt pathway rapidly (within minutes) phosphorylate and inhibit activity of the Polycomb group protein enhancer of zeste homolog 2 (Ezh2). Over the course of 24 to 48 hours, androgens then induce expression of the microRNA miR-101, which targets Ezh2 messenger RNA (mRNA), leading to a nearly complete loss of Ezh2 protein expression. This long-term androgen-induced loss of Ezh2 actions ultimately results in sustained reduction of the H3K27me3-repressive mark in the promoter region of the Runt-related transcription factor-1 (Runx1) gene, a luteinizing hormone (LH)-induced transcription factor essential for ovulation, leading to increased Runx1 mRNA expression. Accordingly, blocking androgen-induced inhibition of Ezh2 in vivo adversely affects LH-induced Runx1 mRNA expression and subsequent ovulation. Importantly, although estrogen treatment of granulosa cells similarly causes rapid activation of the PI3K/Akt pathway and short-term phosphorylation of Ezh2, it does not induce miR-101 expression and thereby does not reduce overall Ezh2 expression, demonstrating the androgen specificity of long-term Ezh2 suppression. Thus, this study provides insight regarding how androgen-induced extranuclear kinase signaling and intranuclear transcription through Ezh2 modifications may influence the expression pattern of genes, ultimately affecting various downstream physiological processes.