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Heterochromatin

About: Heterochromatin is a(n) research topic. Over the lifetime, 6782 publication(s) have been published within this topic receiving 340476 citation(s). The topic is also known as: GO:0000792.

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Journal ArticleDOI
15 May 2009-Science
TL;DR: It is shown that, as well as 5mC in mammalian genomes, there are also significant amounts of 5-hydroxymethylcytosine (5hmC) in DNA of Purkinje neurons, which have large nuclei with apparently very little heterochromatin.

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Abstract: Despite the importance of epigenetic regulation in neurological disorders, little is known about neuronal chromatin. Cerebellar Purkinje neurons have large and euchromatic nuclei, whereas granule cell nuclei are small and have a more typical heterochromatin distribution. While comparing the abundance of 5-methylcytosine in Purkinje and granule cell nuclei, we detected the presence of an unusual DNA nucleotide. Using thin-layer chromatography, high-pressure liquid chromatography, and mass spectrometry, we identified the nucleotide as 5-hydroxymethyl-2′-deoxycytidine (hmdC). hmdC constitutes 0.6% of total nucleotides in Purkinje cells, 0.2% in granule cells, and is not present in cancer cell lines. hmdC is a constituent of nuclear DNA that is highly abundant in the brain, suggesting a role in epigenetic control of neuronal function.

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2,378 citations


Journal ArticleDOI
Tom Volpe1, Catherine A. Kidner, Ira M. Hall2, Ira M. Hall1  +4 moreInstitutions (2)
13 Sep 2002-Science
TL;DR: It is proposed that double-stranded RNA arising from centromeric repeats targets formation and maintenance of heterochromatin through RNAi.

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Abstract: Eukaryotic heterochromatin is characterized by a high density of repeats and transposons, as well as by modified histones, and influences both gene expression and chromosome segregation. In the fission yeast Schizosaccharomyces pombe, we deleted the argonaute, dicer, and RNA-dependent RNA polymerase gene homologs, which encode part of the machinery responsible for RNA interference (RNAi). Deletion results in the aberrant accumulation of complementary transcripts from centromeric heterochromatic repeats. This is accompanied by transcriptional de-repression of transgenes integrated at the centromere, loss of histone H3 lysine-9 methylation, and impairment of centromere function. We propose that double-stranded RNA arising from centromeric repeats targets formation and maintenance of heterochromatin through RNAi.

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2,069 citations


Journal ArticleDOI
19 Jun 2003-Nature
TL;DR: The male-specific region of the Y chromosome, the MSY, differentiates the sexes and comprises 95% of the chromosome's length, and is a mosaic of heterochromatic sequences and three classes of euchromatics sequences: X-transposed, X-degenerate and ampliconic.

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Abstract: The male-specific region of the Y chromosome, the MSY, differentiates the sexes and comprises 95% of the chromosome's length. Here, we report that the MSY is a mosaic of heterochromatic sequences and three classes of euchromatic sequences: X-transposed, X-degenerate and ampliconic. These classes contain all 156 known transcription units, which include 78 protein-coding genes that collectively encode 27 distinct proteins. The X-transposed sequences exhibit 99% identity to the X chromosome. The X-degenerate sequences are remnants of ancient autosomes from which the modern X and Y chromosomes evolved. The ampliconic class includes large regions (about 30% of the MSY euchromatin) where sequence pairs show greater than 99.9% identity, which is maintained by frequent gene conversion (non-reciprocal transfer). The most prominent features here are eight massive palindromes, at least six of which contain testis genes.

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1,913 citations


Journal ArticleDOI
Masashi Narita1, Sabrina Nuñez1, Sabrina Nuñez2, Edith Heard3  +6 moreInstitutions (3)
13 Jun 2003-Cell
TL;DR: A distinct heterochromatic structure that accumulates in senescent human fibroblasts is described, which is designated senescence-associated heterochROMatic foci (SAHF) and is associated with the stable repression of E2F target genes.

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Abstract: Cellular senescence is an extremely stable form of cell cycle arrest that limits the proliferation of damaged cells and may act as a natural barrier to cancer progression. In this study, we describe a distinct heterochromatic structure that accumulates in senescent human fibroblasts, which we designated senescence-associated heterochromatic foci (SAHF). SAHF formation coincides with the recruitment of heterochromatin proteins and the retinoblastoma (Rb) tumor suppressor to E2F-responsive promoters and is associated with the stable repression of E2F target genes. Notably, both SAHF formation and the silencing of E2F target genes depend on the integrity of the Rb pathway and do not occur in reversibly arrested cells. These results provide a molecular explanation for the stability of the senescent state, as well as new insights into the action of Rb as a tumor suppressor.

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1,886 citations


Journal ArticleDOI
André Verdel1, Songtao Jia2, Scott A. Gerber1, Tomoyasu Sugiyama2  +3 moreInstitutions (2)
30 Jan 2004-Science
TL;DR: The purification of an RNAi effector complex termed RITS (RNA-induced initiation of transcriptional gene silencing) that is required for heterochromatin assembly in fission yeast is described and a mechanism for the role of the RNAi machinery and small RNAs in targeting of heterochROMatin complexes and epigenetic genesilencing at specific chromosomal loci is suggested.

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Abstract: RNA interference (RNAi) is a widespread silencing mechanism that acts at both the posttranscriptional and transcriptional levels. Here, we describe the purification of an RNAi effector complex termed RITS (RNA-induced initiation of transcriptional gene silencing) that is required for heterochromatin assembly in fission yeast. The RITS complex contains Ago1 (the fission yeast Argonaute homolog), Chp1 (a heterochromatin-associated chromodomain protein), and Tas3 (a novel protein). In addition, the complex contains small RNAs that require the Dicer ribonuclease for their production. These small RNAs are homologous to centromeric repeats and are required for the localization of RITS to heterochromatic domains. The results suggest a mechanism for the role of the RNAi machinery and small RNAs in targeting of heterochromatin complexes and epigenetic gene silencing at specific chromosomal loci.

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1,226 citations


Network Information
Related Topics (5)
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Satellite DNA

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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20221
2021313
2020320
2019318
2018266
2017249

Top Attributes

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Topic's top 5 most impactful authors

Shiv I. S. Grewal

50 papers, 12.3K citations

Gary H. Karpen

40 papers, 6.2K citations

Sarah C. R. Elgin

40 papers, 6.1K citations

Igor F. Zhimulev

34 papers, 1K citations

Susan M. Gasser

33 papers, 3.8K citations