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MethlyC-Seq of wild type (with 35S-SUC2 transgene) and idm3-1, mbd7-1 mutants (same 35S-SUC2 background)

ABSTRACT: In eukaryotes, heterochromatin is characterized by numerous epigenetic marks, including DNA methylation. Spreading of these marks into nearby active genes must be avoided in order to maintain appropriate gene expression. Here, we uncover Arabidopsis Methyl-CpG-Binding Domain 7 (MBD7) and Increased DNA Methylation 3 (IDM3) as anti-silencing factors that prevent transgene repression and genome-wide DNA hypermethylation. MBD7 preferentially binds to highly methylated, CG-dense regions associated with non-CG methylation and physically associates with other anti-silencing factors, including the histone acetyltransferase IDM1, IDM2, and IDM3. IDM1 and IDM2 were previously shown to facilitate active DNA demethylation by the 5-methylcytosine DNA glycosylase/lyase ROS1. Thus, MBD7 tethers the IDM proteins to methylated DNA, which enables the function of DNA demethylases that in turn establish chromatin boundaries and limit DNA methylation Using MethylC-Seq to provide single-base resolution of DNA methylation status in WT and idm3-1, mbd7-1 mutants

ORGANISM(S): Arabidopsis thaliana

PROVIDER: GSE58787 | GEO | 2015/01/29

SECONDARY ACCESSION(S): PRJNA253489

REPOSITORIES: GEO

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Project description:DNA methylation is a chromatin modification that is associated with gene silencing in eukaryotic organisms. Although pathways controlling the establishment, maintenance and removal of DNA methylation have been identified, relatively little is understood about how DNA methylation influences gene expression. Using complementary genetic and biochemical approaches we identified a protein complex that antagonizes the transcriptional gene silencing of two LUCIFERASE (LUC) reporters in a manner that requires DNA methylation. At its core, this complex contains LOW IN LUCIFERASE EXPRESSION (LIL), an α-crystallin domain protein, and METHYL-CpG-BINDING DOMAIN 7 (MBD7), a protein previously associated with DNA methylation. At the LUC reporters, loss of MBD7 or LIL resulted in decreased LUC expression concomitant with modest, but reproducible increases in DNA methylation that can be phenocopied by DNA demethylase mutants. These findings are consistent with other reports and reveal a genetic connection between MBD7, LIL and DNA demethylation. However, we found that the hyper-methylation and gene expression phenotypes at a LUC reporter can be genetically uncoupled, demonstrating that changes in DNA methylation alone are not sufficient to silence LUC expression, and suggesting a role for the MBD7-LIL complex downstream of DNA methylation. Consistent with this hypothesis, our more extensive analysis of DNA methylation in mbd7 and lil mutants revealed only a small number of hyper-methylated loci genome wide. Furthermore, these loci displayed minimal overlap with demethylase targets, suggesting that, in general, the DNA demethylation machinery does not function in a manner dependent on the MBD7-LIL complex. Taken together, our findings place the MBD7-LIL complex amongst a small number of factors that regulate gene expression without causing significant changes in DNA methylation. This complex, however, is unique in that it functions to suppress, rather than enforce the silencing effects of DNA methylation, enabling gene expression of several transgene reporters despite high levels of promoter methylation.

Dataset Information

MethlyC-Seq of wild type (with 35S-SUC2 transgene) and idm3-1, mbd7-1 mutants (same 35S-SUC2 background)

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