Summary
Polycomb group (PcG) proteins exist in distinct multi-protein complexes and play a central role in silencing developmental genes, yet the underlying mechanisms remain elusive. Here, we show that deficiency of retinoblastoma binding protein 4 (RBBP4), a component of the Polycomb repressive complex 2 (PRC2), in embryonic stem cells (ESCs) leads to spontaneous differentiation into mesendodermal lineages. We further show that
Rbbp4
and core PRC2 share an important number of common genomic targets, encoding regulators involved in early germ layer specification. Moreover, we find that
Rbbp4
is absolutely essential for genomic targeting of PRC2 to a subset of developmental genes. Interestingly, we demonstrate that
Rbbp4
is necessary for sustaining the expression of
Oct4
and
Sox2
and that the forced co-expression of
Oct4
and
Sox2
fully rescues the pluripotency of
Rbbp4
-null ESCs. Therefore, our study indicates that
Rbbp4
links maintenance of the pluripotency regulatory network with repression of mesendoderm lineages.