异染色质
染色质
异染色质蛋白1
生物
组蛋白H3
DNA甲基化
组蛋白
拟南芥
组蛋白甲基转移酶
组蛋白甲基化
甲基转移酶
甲基化
遗传学
细胞生物学
DNA
突变体
基因
基因表达
作者
Yannick Jacob,Suhua Feng,Chantal LeBlanc,Yana V. Bernatavichute,Hume Stroud,Shawn J. Cokus,Lianna M. Johnson,Matteo Pellegrini,Steven E. Jacobsen,Scott D. Michaels
摘要
Constitutive heterochromatin in Arabidopsis thaliana is marked by repressive chromatin modifications, including DNA methylation, histone H3 dimethylation at Lys9 (H3K9me2) and monomethylation at Lys27 (H3K27me1). The enzymes catalyzing DNA methylation and H3K9me2 have been identified; alterations in these proteins lead to reactivation of silenced heterochromatic elements. The enzymes responsible for heterochromatic H3K27me1, in contrast, remain unknown. Here we show that the divergent SET-domain proteins ARABIDOPSIS TRITHORAX-RELATED PROTEIN 5 (ATXR5) and ATXR6 have H3K27 monomethyltransferase activity, and atxr5 atxr6 double mutants have reduced H3K27me1 in vivo and show partial heterochromatin decondensation. Mutations in atxr5 and atxr6 also lead to transcriptional activation of repressed heterochromatic elements. Notably, H3K9me2 and DNA methylation are unaffected in double mutants. These results indicate that ATXR5 and ATXR6 form a new class of H3K27 methyltransferases and that H3K27me1 represents a previously uncharacterized pathway required for transcriptional repression in Arabidopsis.
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