Abstract
Active DNA demethylation is an important part of epigenetic regulation in plants and animals. How active DNA demethylation is regulated and its relationship with histone modification patterns are unclear. Here, we report the discovery of IDM1, a regulator of DNA demethylation in Arabidopsis. IDM1 is required for preventing DNA hypermethylation of highly homologous multicopy genes and other repetitive sequences that are normally targeted for active DNA demethylation by Repressor of Silencing 1 and related 5-methylcytosine DNA glycosylases. IDM1 binds methylated DNA at chromatin sites lacking histone H3K4 di- or trimethylation and acetylates H3 to create a chromatin environment permissible for 5-methylcytosine DNA glycosylases to function. Our study reveals how some genes are indicated by multiple epigenetic marks for active DNA demethylation and protection from silencing.
Highlights
Active DNA demethylation is an important part of epigenetic regulation in plants and animals
A large body of literature concerns the regulation of DNA methylation by histone modification patterns [1, 2], little is known about the regulation of active DNA demethylation
From an independent genetic screen for mutants impaired in the prevention of silencing of the 35S-NPTII transgene, we found the idm1-3 mutation that changes glutamic acid-451 to a premature stop codon and causes the silencing of 35S-NPTII but not the RD29A-LUC transgene
Summary
Active DNA demethylation is an important part of epigenetic regulation in plants and animals. Two of the identified mutants (Fig. 1A), referred to as idm1 (for increased DNA methylation 1), have T-DNA insertions in the gene At3g14980 Double-mutant analysis indicated that the DNA hypermethylation phenotypes of ros1-4 and idm1-1 are not additive
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