Regulation of heterochromatic DNA replication by histone H3 lysine 27 methyltransferases

Abstract

Multiple pathways prevent DNA replication from occurring more than once per cell cycle1. These pathways block re-replication by strictly controlling the activity of pre-replication complexes, which assemble at specific sites in the genome called origins. Here we show that mutations in the homologous histone 3 lysine 27 (H3K27) monomethyltransferases, ARABIDOPSIS TRITHORAX-RELATED PROTEIN5 (ATXR5) and ATXR6, lead to re-replication of specific genomic locations. The vast majority of these locations correspond to transposons and other repetitive and silent elements of the Arabidopsis genome. These sites also correspond to high levels of H3K27 monomethylation, and mutation of the catalytic SET domain is sufficient to cause the re-replication defect. Mutation of ATXR5 and ATXR6 also causes upregulation of transposon expression and has pleiotropic effects on plant development. These results uncover a novel pathway that prevents over-replication of heterochromatin in Arabidopsis.

High-resolution mapping of H4K16 and H3K23 acetylation reveals conserved and unique distribution patterns inArabidopsisand rice

“…H4K16ac is positively correlated with active marks (H3K9ac, H3K18ac, H3K4me2/3 and H3K36me2/3 15,[42][43][44] ) and anti-correlated with repressive modifications (H3K27me1 and H3K9me2 15,45 ) and histone variants H3.1 and H2A.W, which are required for heterochromatin condensation ( Fig. 2A).…”

Multiple Functions of Kip-Related Protein5 Connect Endoreduplication and Cell Elongation

“…Moreover, these proteins can act to suppress DNA rereplication in heterochromatic regions of the Arabidopsis genome (Jacob et al, 2010). Because we found KRP5 to bind to heterochromatin, we asked whether this association could also participate in the control of endoreduplication.…”

Regulating DNA Replication in Plants

“…Thus, ATXR5 and ATXR6, encoded by E2F target genes, are monomethyl H3K27 transferases that interact with PCNA (Raynaud et al 2006;Jacob et al 2009). Massive sequencing of sorted 2 -16C nuclei of an atxr5 atxr6 double mutant revealed, surprisingly, a significant increase (.30%) in the amount of pericentromeric heterochromatic sequences (Jacob et al 2010). In fact, the PCNA-interacting protein (PIP) motif of ATXR5 and ATXR6 is required to prevent the rereplication phenotype (Jacob et al 2010).…”

“…Massive sequencing of sorted 2 -16C nuclei of an atxr5 atxr6 double mutant revealed, surprisingly, a significant increase (.30%) in the amount of pericentromeric heterochromatic sequences (Jacob et al 2010). In fact, the PCNA-interacting protein (PIP) motif of ATXR5 and ATXR6 is required to prevent the rereplication phenotype (Jacob et al 2010). Moreover, the rereplicated sequences are preferentially located at specific loci, suggesting a heterochromatin-specific loss of licensing control, although dispersed heterochromatic regions across chromosome arms also show rereplicated material.…”