Clustered PHD domains in mixed lineage leukaemia proteins are attracted by acetylation-rich active promoters and enhancers

Abstract

Histone lysine-specfic methyltransferase 2 (KMT2A-D) proteins, alternatively called mixed lineage leukaemia (MLL1-4) proteins, mediate positive transcriptional memory. As the catalytic subunits of human COMPASS-like complexes, they methylate H3K4 at promoters and enhancers. KMT2A-D contain understudied highly conserved triplets and a quartet of plant homeodomains (PHDs). Here, we show that all clustered PHDs localise to the well-defined loci of H3K4me3 and H3 acetylation-rich active promoters and enhancers. Surprisingly, we observe little difference in binding pattern between PHDs from promoter-specific KMT2A-B and enhancer-specific KMT2C-D. Fusion of the KMT2A CXXC domain to the PHDs drastically enhances their preference for promoters over enhancers. Hence, the presence of CXXC domains in KMT2A-B, but not KMT2C-D, may explain the promoter/enhancer preferences of the full-length proteins. Importantly, targets of PHDs overlap with KMT2A targets and are enriched in genes involved in the cancer pathways. We also observe that PHDs of KMT2A-D are mutated in cancer, especially within conserved folding motifs (Cys4HisCys2Cys/His), which cause a domain loss-of-function. Taken together, our data suggests that PHDs of KMT2A-D guide the full-length proteins to active promoters and enhancers, and thus play a role in positive transcriptional memory. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=123 SRC="FIGDIR/small/462366v2_ufig1.gif" ALT="Figure 1"> View larger version (30K): org.highwire.dtl.DTLVardef@1d62842org.highwire.dtl.DTLVardef@ed1041org.highwire.dtl.DTLVardef@1c62b43org.highwire.dtl.DTLVardef@1426bcd_HPS_FORMAT_FIGEXP M_FIG C_FIG