Document Detail

RNA-directed DNA methylation and Pol IVb in Arabidopsis.
MedLine Citation:
PMID:  17381327     Owner:  NLM     Status:  MEDLINE    
Recent work in Arabidopsis has revealed a plant-specific RNA polymerase, pol IV, that is specialized for RNA interference (RNAi)-mediated, chromatin-based gene silencing. Two functionally diversified pol IV complexes have been identified: pol IVa is required to produce or amplify the small RNA trigger, whereas pol IVb, together with the plant-specific SWI/SNF-like chromatin remodeling factor DRD1, acts downstream from small RNA formation to induce de novo cytosine methylation of homologous DNA by an unknown mechanism. Retrotransposon long terminal repeats (LTRs) and other unannotated sequences that encode small RNAs are prime targets for DRD1/pol IVb-mediated cytosine methylation. In drd1 and pol IVb mutants, silent LTRs in euchromatin can be derepressed, resulting in enhanced transcription of adjacent genes or intergenic regions. In addition to mediating de novo methylation, some evidence suggests that DRD1 and pol IVb are also involved in a reciprocal process of active demethylation, perhaps in conjunction with DNA glycosylase domain-containing proteins such as ROS1. We speculate that DRD1/pol IV-dependent methylation/demethylation evolved in the plant kingdom as a means to facilitate rapid, reversible changes in gene expression, which might have adaptive significance for immobile plants growing in unpredictable environments.
M Matzke; T Kanno; B Huettel; L Daxinger; A J M Matzke
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't; Review    
Journal Detail:
Title:  Cold Spring Harbor symposia on quantitative biology     Volume:  71     ISSN:  0091-7451     ISO Abbreviation:  Cold Spring Harb. Symp. Quant. Biol.     Publication Date:  2006  
Date Detail:
Created Date:  2007-03-26     Completed Date:  2007-06-21     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  1256107     Medline TA:  Cold Spring Harb Symp Quant Biol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  449-59     Citation Subset:  IM    
Gregor Mendel Institute of Molecular Plant Biology, Austrian Academy of Sciences, Vienna, Austria.
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MeSH Terms
Arabidopsis / genetics*,  metabolism*
Arabidopsis Proteins / genetics,  metabolism
Base Sequence
CpG Islands
DNA Methylation*
DNA, Plant / chemistry,  genetics,  metabolism
DNA-Directed RNA Polymerases / genetics,  metabolism*
Gene Silencing
Models, Biological
RNA Interference
RNA, Plant / genetics,  metabolism
Terminal Repeat Sequences
Reg. No./Substance:
0/Arabidopsis Proteins; 0/DNA, Plant; 0/RNA, Plant; EC 2.7.7.-/RNA polymerase IV, Arabidopsis; EC RNA Polymerases; EC protein, Arabidopsis

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