Association of modified cytosines and the methylated DNA-binding protein MeCP2 with distinctive structural domains of lampbrush chromatin
UMass Chan Affiliations
Department of Cell and Developmental BiologyDocument Type
Journal ArticlePublication Date
2012-12-01Keywords
5-Methylcytosine; Animals; Chromatin; Chromosomes; Cytosine; DNA; DNA Methylation; Gene Expression Regulation; Humans; Immunoblotting; Methyl-CpG-Binding Protein 2; Mutation; Oocytes; RNA Polymerase II; Sequence Analysis, DNA; Transcription, Genetic; Xenopus laevisLampbrush chromosomes
Methylation
5-hydroxymethylcytosine
Oocyte
Transcription unit
Cell Biology
Developmental Biology
Molecular Biology
Molecular Genetics
Musculoskeletal Diseases
Nervous System Diseases
Metadata
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We have investigated the association of DNA methylation and proteins interpreting methylation state with the distinctive closed and open chromatin structural domains that are directly observable in the lampbrush chromosomes (LBCs) of amphibian oocytes. To establish the distribution in LBCs of MeCP2, one of the key proteins binding 5-methylcytosine-modified DNA (5mC), we expressed HA-tagged MeCP2 constructs in Xenopus laevis oocytes. Full-length MeCP2 was predominantly targeted to the closed, transcriptionally inactive chromomere domains in a pattern proportional to chromomeric DNA density and consistent with a global role in determining chromatin state. A minor fraction of HA-MeCP2 was also found to associate with a distinctive structural domain, namely a short region at the bases of some of the extended lateral loops. Expression in oocytes of deleted constructs and of point mutants derived from Rett syndrome patients demonstrated that the association of MeCP2 with LBCs was determined by its 5mC-binding domain. We also examined more directly the distribution of 5mC by immunostaining Xenopus and axolotl LBCs and confirmed the pattern suggested by MeCP2 targeting of intense staining of the chromomeres and of some loop bases. In addition, we found in the longer loops of axolotl LBCs that short interstitial regions could also be clearly stained for 5mC. These 5mC regions corresponded precisely to unusual segments of active transcription units from which RNA polymerase II (pol II) and nascent transcripts were simultaneously absent. We also examined by immunostaining the distribution in lampbrush chromatin of the oxidized 5mC derivative, 5-hydroxymethylcytosine (5hmC). Although in general, the pattern resembled that obtained for 5mC, one antibody against 5hmC produced intense staining of restricted chromosomal foci. These foci corresponded to a third type of lampbrush chromatin domain, the transcriptionally active but less extended structures formed by clusters of genes transcribed by pol III. This raises the possibility that 5hmC may play a role in establishing the distinctive patterns of gene repression and activation that characterize specific pol III-transcribed gene families in amphibian genomes.Source
Chromosome Res. 2012 Dec;20(8):925-42. doi: 10.1007/s10577-012-9324-x. Link to article on publisher's siteDOI
10.1007/s10577-012-9324-xPermanent Link to this Item
http://hdl.handle.net/20.500.14038/43879PubMed ID
23149574Notes
At the time of publication, Peter Jones was not yet affiliated with the University of Massachusetts Medical School.
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Copyright © The Author(s) 2012. This article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution, and reproduction in any medium, provided the original author(s) and the source are credited.
ae974a485f413a2113503eed53cd6c53
10.1007/s10577-012-9324-x