A structural role for histone methyltransferase MET-2 represses transcription independent of H3K9me catalysis [ChIP-seq]

Packaging genomic regions into silenced heterochromatin is critical to maintain organismal viability and tissue identity. Methylation of histone H3 on lysine 9 (H3K9me) marks heterochromatin. Here we show that in addition to catalyzing H3K9me, the C. elegans histone methyltransferase MET-2 (SETDB1-like) has a second non-catalytic function that can itself contribute to gene repression. We find that subnuclear concentrates, or foci, of MET-2 correlate with efficient HMT activity, yet foci composed of catalytic-deficient MET-2 are also able to mediate transcriptional silencing. Genetic ablation of met-2 or physiological disruption of MET-2 foci by heat stress results in loss of silencing coincident with an increase in histone acetylation. Restoration of catalytically deficient MET-2 foci mitigates H3K9 and H3K27 hyperacetylation, gene derepression, and infertility, demonstrating a structural role for foci of a conserved heterochromatic histone methyltransferase in gene silencing independent of its enzymatic activity. Overall design: ChIP experiments of H3K27ac and H3K9me2 in wild-type (N2), met-2(n4256) III and met-2(gw1660) III. Libraries were prepared from chromatin IP and input samples using the NEBNext ultra DNA library prep kit for Illumina (NEB # 7370) and the NEBNext Multiplex Oligos for Illumina (NEB # E7335), according to the manufacturer?s recommendations. No size selection was performed during sample preparation and the libraries were indexed and amplified using 12 PCR cycles, using the recommended conditions. After a final cleanup with Agencourt AmPure XP beads (Beckman # A63881), the library size distribution and concentrations were determined using a BioAnalyzer 2100 (Agilent technologies) and Qubit (Invitrogen) instrument, respectively. The final pools were prepared by mixing equimolar amounts of all individual indexed libraries and then sequenced on a HiSeq 2500 (Illumina) in Rapid mode (Paired-End 50).