Systematic characterization of chromodomain proteins revealsan H3K9me1/2 reader regulating aging in C. elegans

Abstract

The chromatin organization modifier domain (chromodomain) is an evolutionally conserved motif across eukaryotic species. The chromodomain mainly functions as a histone methyl-lysine reader to modulate gene expression, chromatin spatial conformation and genome stability. Mutations or aberrant expression of chromodomain proteins can result in cancer and other human diseases. Here, we systematically tagged chromodomain proteins with green fluorescent protein (GFP) using CRISPR/Cas9 technology in C. elegans. By combining ChIP-seq analysis and imaging, we delineated a comprehensive expression and functional map of chromodomain proteins. We then conducted a candidate-based RNAi screening and identified factors that regulate the expression and subcellular localization of the chromodomain proteins. Specifically, we revealed a new H3K9me1/2 reader, CEC-5, both by in vitro biochemistry and in vivo ChIP assays. MET-2, an H3K9me1/2 writer, is required for CEC-5 association with heterochromatin. Both MET-2 and CEC-5 are required for the normal lifespan of C. elegans. Furthermore, a forward genetic screening identified a conserved Arginine124 of CEC-5s chromodomain, which was essential for CEC-5s association with chromatin and life span regulation. Thus, our work will serve as a reference to explore chromodomain functions and regulation in C. elegans and allow potential applications in aging-related human diseases.