シロイヌナズナにおける7つのH3K4メチルトランスフェラーゼのクロマチンターゲティング機構の比較特性評価

Methylation of histone H3 at lysine 4 (H3K4me) marks transcribed elements of the eukaryotic genome, and its distribution dynamically changes through developmental stages and in response to environmental factors. These dynamic regulatory changes are achieved by the combinatorial action of H3K4me methyltransferases, with multi-cellular organisms carrying multiple copies of these enzymes. The model plant Arabidopsis has at least seven H3K4 methyltransferase genes. Here, we comparatively analyze the seven H3K4 methyltransferases using epigenomics and biochemical approaches to better understand the mechanisms underlying their target specificity. Our findings, in combination with previous work, show that ATX1 to ATX5 (Trx/Trr-type methyltransferases) localize to loci with distinct sets of chromatin modifications and DNA motifs, which differ among the various ATX proteins. Notably, ATX3 localizes to the binding motifs of ASR3 and RAP2.11 transcriptional factors and directly interacts with these TFs. ATXR7 (Set1-type) and ATXR3 (non-canonical H3K4 methyltransferase) co-localize with the transcriptional machinery, suggesting co-transcriptional mechanisms of action for these enzymes. Interestingly, ATXR3, the major H3K4me3 methyltransferase in Arabidopsis, appears to form a protein complex independent of COMPASS, indicating that the regulatory mechanisms of H3K4me3 have diverged between plants and animals. Our work provides a foundation for understanding the chromatin targeting of H3K4 methyltransferases in plants and highlights significant differences in H3K4me3 regulation between plants and other eukaryotes.