Variant Polycomb complexes in <i>Drosophila</i> consistent with ancient functional diversity

Abstract

Polycomb group (PcG) mutants were first identified in <i>Drosophila</i> on the basis of their failure to maintain proper <i>Hox</i> gene repression during development. The proteins encoded by the corresponding fly genes mainly assemble into one of two discrete Polycomb repressive complexes: PRC1 or PRC2. However, biochemical analyses in mammals have revealed alternative forms of PRC2 and multiple distinct types of noncanonical or variant PRC1. Through a series of proteomic analyses, we identify analogous PRC2 and variant PRC1 complexes in <i>Drosophila</i>, as well as a broader repertoire of interactions implicated in early development. Our data provide strong support for the ancient diversity of PcG complexes and a framework for future analysis in a longstanding and versatile genetic system.