Abstract
Polycomb Repressive Complex 2 (PRC2) catalyzes the mono-, di, and trimethylation of histone protein H3 on lysine 27 (H3K27). Trimethylation of H3K27 is strongly associated with transcriptionally silent chromatin and plays an important role in the regulation of cell identity and developmental gene expression1. The functional core of PRC2 is highly conserved in animals and consists of four subunits1 (Fig. 1a). Notably, one of these subunits, SUZ12, has not been identified in the genetic model Caenorhabditis elegans, whereas C. elegans PRC2 contains the lineage-specific protein MES-32,3 (Fig. 1a). Here, we demonstrate that MES-3 is in fact a highly divergent ortholog of SUZ12. Unbiased sensitive sequence similarity searches uncovered consistent but insignificant reciprocal best matches between MES-3 and SUZ12, suggesting that these proteins could share a common evolutionary history. We substantiate this hypothesis by directly comparing the predicted structures of SUZ12 and MES-3, which revealed shared protein folds and residues of key domains. Thus, in agreement with the observations in previous genetic and biochemical studies2,3, we here provide evidence that C. elegans, like other animals, contains a diverged yet evolutionary conserved core PRC2.
Competing Interest Statement
The authors have declared no competing interest.