Structural basis of transcriptional gene silencing mediated by Arabidopsis MOM1

Shifts between epigenetic states of transcriptional activity are typically correlated with changes in epigenetic marks. However, exceptions to this rule suggest the existence of additional, as yet uncharacterized, layers of epigenetic regulation. MOM1, a protein of 2,001 amino acids that acts as a t...

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Bibliographic Details
Published in:PLoS genetics 2012-02, Vol.8 (2), p.e1002484
Main Authors: Nishimura, Taisuke, Molinard, Guillaume, Petty, Tom J, Broger, Larissa, Gabus, Caroline, Halazonetis, Thanos D, Thore, Stéphane, Paszkowski, Jerzy
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Arabidopsis - chemistry
Arabidopsis - genetics
Arabidopsis Proteins - chemistry
Arabidopsis Proteins - genetics
Arabidopsis thaliana
Biology
Crystallography, X-Ray
Deoxyribonucleic acid
Derivatives
DNA
DNA methylation
Efficiency
Epigenesis, Genetic - genetics
Epigenetics
Experiments
Gene Expression Regulation, Plant
Gene Silencing
Genes
Genetic aspects
Genetic engineering
Genetic transcription
Molecular Sequence Data
Mutagenesis
Nuclear Proteins - chemistry
Nuclear Proteins - genetics
Plants, Genetically Modified
Protein Conformation
Protein Folding
Protein Multimerization
Protein Structure, Tertiary - genetics
Proteins
RNA, Small Interfering - genetics
Structure-Activity Relationship
Transcription Factors - chemistry
Transcription Factors - genetics
Transcription, Genetic
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Summary:Shifts between epigenetic states of transcriptional activity are typically correlated with changes in epigenetic marks. However, exceptions to this rule suggest the existence of additional, as yet uncharacterized, layers of epigenetic regulation. MOM1, a protein of 2,001 amino acids that acts as a transcriptional silencer, represents such an exception. Here we define the 82 amino acid domain called CMM2 (Conserved MOM1 Motif 2) as a minimal MOM1 fragment capable of transcriptional regulation. As determined by X-ray crystallography, this motif folds into an unusual hendecad-based coiled-coil. Structure-based mutagenesis followed by transgenic complementation tests in plants demonstrate that CMM2 and its dimerization are effective for transcriptional suppression at chromosomal loci co-regulated by MOM1 and the siRNA pathway but not at loci controlled by MOM1 in an siRNA-independent fashion. These results reveal a surprising separation of epigenetic activities that enable the single, large MOM1 protein to coordinate cooperating mechanisms of epigenetic regulation.
ISSN:1553-7404
1553-7390
1553-7404
DOI:10.1371/journal.pgen.1002484