Evolutionarily ancient BAH-PHD protein mediates Polycomb silencing.

Wiles, Elizabeth T; McNaught, Kevin J; Kaur, Gurmeet; Selker, Jeanne M L; Ormsby, Tereza; Aravind, L; Selker, Eric U · Proc Natl Acad Sci U S A · 2020

basic_science · Level V

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Abstract

Methylation of histone H3 lysine 27 (H3K27) is widely recognized as a transcriptionally repressive chromatin modification but the mechanism of repression remains unclear. We devised and implemented a forward genetic scheme to identify factors required for H3K27 methylation-mediated silencing in the filamentous fungus <i>Neurospora crassa</i> and identified a bromo-adjacent homology (BAH)-plant homeodomain (PHD)-containing protein, EPR-1 (effector of polycomb repression 1; NCU07505). EPR-1 associates with H3K27-methylated chromatin, and loss of EPR-1 de-represses H3K27-methylated genes without loss of H3K27 methylation. EPR-1 is not fungal-specific; orthologs of EPR-1 are present in a diverse array of eukaryotic lineages, suggesting an ancestral EPR-1 was a component of a primitive Polycomb repression pathway.

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