Polycomb-like 2 associates with PRC2 and is required for mouse embryonic stem cell

Polycomb group (PcG) proteins are highly conserved epigenetic transcriptional repressors important for the control of numerous developmental gene expression programs and have recently been implicated in the modulation of embryonic stem cell (ESC) identity. We identified the PcG protein PCL2 (polycomb-like 2) in a genome-wide screen for novel regulators of self-renewal and pluripotency and predicted that it would play an important role in mouse ESC fate determination. Using multiple biochemical strategies, we provide evidence that PCL2 is a novel Polycomb Repressive Complex 2 (PRC2)-associated protein in mouse ESCs. Knockdown of Pcl2 in ESCs resulted in heightened self-renewal characteristics, defects in differentiation and altered patterns of histone methylation. Through integration of global gene expression and promoter occupancy analyses of both PCL2 and PRC2 components EZH2 and SUZ12, we have predicted PCL2 target genes and formulated regulatory networks describing the role of PCL2 both in modulating transcription of ESC self-renewal genes in undifferentiated ESCs as well as developmental regulators during early commitment and differentiation.

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