GSE50942
The Histone Variant H2A.W Defines Heterochromatin and Promotes Chromatin Condensation in Arabidopsis
Histone variants play crucial roles in gene expression, genome integrity and chromosome segregation. However, to what extent histone variants control chromatin architecture remains largely unknown.  Here, we show that the previously uncharacterized histone variant H2A.W plays a crucial role in condensation of heterochromatin. Genome-wide profiling of all four types of H2A variants in Arabidopsis shows that H2A.W specifically associates with heterochromatin. H2A.W recruitment is independent of heterochromatic marks H3K9me2 and DNA methylation. Genetic interactions show that H2A.W acts in synergy with CMT3 mediated methylation to maintain genome integrity. In vitro, H2A.W enhances chromatin condensation through a higher propensity to make fiber-to-fiber interactions via its conserved C-terminal motif. In vivo, elimination of H2A.W causes decondensation of heterochromatin and conversely, ectopic expression of H2A.W promotes heterochromatin condensation. These results demonstrate that H2A.W plays critical roles in heterochromatin by promoting higher order chromatin condensation. Since similar H2A.W C-terminal motifs are present in other variant found in mammals and other organisms our findings impact our understanding of heterochromatin condensation in a wide variety of eukaryotic organisms. Overall design: Two mRNA-seq samples, two bisulfite-seq samples, six ChIP-seq samples.