Patterns of histone modifications separate animal genomes into broad domains having different activity states but how such domains form is poorly understood. Most of the C. elegans genome is organised into one of two types of broad chromatin domain. H3K27me3 domains overlie genes with regulated expression and these alternate with active domains marked by H3K36me3 and containing genes that are widely and/or germ line expressed (Evans et al 2016). H3K27me3 marking is generated by the Polycomb PRC2 complex, which is known for maintaining transcription repression through the regulation of chromatin structure, and NSD-type histone methyltransferase MES-4 maintains H3K36me3 (Gaydos et al 2012; Rechtsteiner et al 2010; Bender et al 2004). A similar pattern of alternating domains is seen in Drosophila and regions of mammalian genomes (Carelli et al 2018; El-Sharnouby et al, 2017). We study how active and PRC2 chromatin domains form and function.
