Jarid2 and PRC2, Partner in Regulating Gene Expression. Mus musculus

The Polycomb Group proteins foster gene repression profiles required for proper development and unimpaired adulthood, and comprise the components of the PRC2 complex including the histone H3 lysine 27 (H3K27) methyltransferase Ezh2. How mammalian PRC2 accesses chromatin is unclear. We find that Jarid2 associates with PRC2 and stimulates its enzymatic activity in vitro. Jarid2 contains a Jumonji C domain, but is devoid of detectable histone demethylase activity. Instead, its artificial recruitment to a promoter in vivo resulted in co-recruitment of PRC2 with resultant increased levels of H3K27me2/3. Jarid2 co-localizes with Ezh2 and MTF2, a homologue of Drosophila Pcl, at endogenous genes in ES cells. Jarid2 can itself bind DNA and its recruitment in ES cells is interdependent with that of PRC2 as Jarid2 knockdown reduced PRC2 at its target promoters, and ES cells devoid of the PRC2 component EED are deficient in Jarid2 promoter access. In addition to the well-documented defects in embryonic viability upon down-regulation of Jarid2, ES cell differentiation is impaired, as is Oct4 silencing. Overall design: Examination of two factors in ES cells