Mutation of Arabidopsis SMC4 identifies condensin as a corepressor of pericentromeric transposons and conditionally expressed genes.
In eukaryotes, transcriptionally inactive loci are enriched within highly condensed heterochromatin. In plants, as in mammals, the DNA of heterochromatin is densely methylated and wrapped by histones displaying a characteristic subset of post-translational modifications. Growing evidence indicates that these chromatin modifications are not sufficient for silencing. Instead, they are prerequisites for further assembly of higher-order chromatin structures that are refractory to transcription but not fully understood. We show that silencing of transposons in the pericentromeric heterochromatin of Arabidopsis thaliana requires SMC4, a core subunit of condensins I and II, acting in conjunction with CG methylation by MET1 (DNA METHYLTRANSFERASE 1), CHG methylation by CMT3 (CHROMOMETHYLASE 3), the chromatin remodeler DDM1 (DECREASE IN DNA METHYLATION 1), and histone modifications, including histone H3 Lys 27 monomethylation (H3K27me1), imparted by ATXR5 and ATXR6. SMC4/condensin also acts within the mostly euchromatic chromosome arms to suppress conditionally expressed genes involved in flowering or DNA repair, including the DNA glycosylase ROS1, which facilitates DNA demethylation. Collectively, our genome-wide analyses implicate condensin in the suppression of hundreds of loci, acting in both DNA methylation-dependent and methylation-independent pathways.
['Wang|Jing|J|', 'Blevins|Todd|T|', 'Podicheti|Ram|R|', 'Haag|Jeremy R|JR|', 'Tan|Ek Han|EH|', 'Wang|Feng|F|', 'Pikaard|Craig S|CS|0000-0001-8204-7459']
D000251:Adenosine Triphosphatases D017360:Arabidopsis D029681:Arabidopsis Proteins D018385:Centrosome D002843:Chromatin D019175:DNA Methylation D004260:DNA Repair D004251:DNA Transposable Elements D004268:DNA-Binding Proteins D018506:Gene Expression Regulation, Plant D020868:Gene Silencing D055106:Genome-Wide Association Study D060005:Genotyping Techniques D006570:Heterochromatin D006657:Histones D008780:Methyltransferases D046912:Multiprotein Complexes D009154:Mutation D017422:Sequence Analysis, DNA D017423:Sequence Analysis, RNA
DNA methylation SMC proteins chromosome condensation epigenetic regulation gene silencing heterochromatin formation