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Topic: Constitutive heterochromatin

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Euchromatin

Histone

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	BERC Publications: A few words about DNA and chromatin (Site not responding. Last check: 2007-10-19)
		Facultative heterochromatin is condensed chromatin that unfolds and becomes transcriptionally active during some portion of the cell cycle.
		Constitutive heterochromatin refers to the chromatin that remains transcriptionally inert during the entire cell cycle.
		The bulk of constitutive heterochromatin is composed of non-coding DNA sequences that are repeated hundreds of thousands or even millions of times.
	www.pnl.gov /berc/bg/dna.html (1960 words)

	Deregulation of genetic pathways in neuroendocrine tumors
		Constitutive HC is stable and conserves its heterochromatic properties during all stages of development and in all tissues.
		This heterochromatin protein interacts specifically with the B lamin receptor, which is an integral component of the inner membrane of the nucleus.
		In conclusion, although heterochromatin is apparently amorphous and isolated at the periphery of the nucleus, it appears to have an absolutely essential role in the organisation and function of the genome.
	atlasgeneticsoncology.org /Deep/HeterochromatineDEEP.html (5840 words)

	Introduction to Chromatin (Site not responding. Last check: 2007-10-19)
		Modifications of chromatin histones are usually associated with the regulation of biological processes such as DNA replication, gene expression, chromatin assembly and condensation, and cell division.
		The ultimate answer for the structural-functional motif of chromatin is that when DNA is folded into heterochromatin, it is relatively inaccessible to the polymerases and proteins involved in DNA transcription.
		The conversion of heterochromatin into euchromatin is a necessary step for DNA transcription.
	library.thinkquest.org /C006188/basics/chromatin.htm (374 words)

	Interactive Fly, Drosophila
		Constitutive heterochromatin is marked by distinctive histone H3 methylation and the presence of HP1 proteins, but the chromatin modifications of facultative heterochromatin are less clear.
		Heterochromatin protein 1 (HP1) is a key component of constitutive heterochromatin in Drosophila and is required for stable epigenetic gene silencing classically observed as position effect variegation.
		Heterochromatin protein 1 (HP1) is a major component of heterochromatin and thus is a candidate for establishing and maintaining the transcriptionally repressive heterochromatin structure.
	www.sdbonline.org /fly/polycomb/hp1-2.htm (13249 words)

	Genetic Engineering
		Heterochromatin was originally defined in 1928 by Emil Heitz as chromosomal material (chromatin) that remains condensed during interphase.
		Facultative heterochromatin is active in some tissues and not others, or at some stages in development and not in others (and sometimes in one homologous chromosome and not the other, as in the mammalian female X chromosome), while constitutive heterochromatin seems to be present in most tissues at most times in development.
		Constitutive heterochromatin, on the other hand, appears to be more stable, and thus may be associated with a particular DNA sequence.
	dwb.unl.edu /Teacher/NSF/C08/C08Links/gregor.rutgers.edu/genetics/Week17/Lecture17-1.html (2742 words)

	Progeria.ca - From the Cover: Mutant nuclear lamin A leads to progressive alterations of epigenetic contro l in ...
		To determine the mechanisms responsible for the loss of heterochromatin, epigenetic marks regulating either facultative or constitutive heterochromatin were examined.
		The results also show a down-regulation of the pericentric constitutive heterochromatin mark, histone H3 trimethylated on lysine 9, and an altered association of this mark with heterochromatin protein 1alpha (Hp1alpha) and the CREST antigen.
		This loss of con stitutive heterochromatin is accompanied by an up-regulation of pericentric satellite III repeat transcripts.
	www.progeria.ca /index.php?categoryid=11&p2_articleid=125 (286 words)

	Botany online: Changes - Molecular Level - Impacts on the Evolution - Chromosomal Banding Patterns (Site not responding. Last check: 2007-10-19)
		The bandings containing heterochromatin or histone-DNA-complexes, respectively, can easily be stained with conventional chromosome dyes (orcein in this case) and are thus simple to identify (upper picture).
		Heterochromatin binds a lot of the dye, while the rest of the chromosomes absorb only little of it.
		he consistent banding patterns of the constitutive heterochromatin and the remaining chromatin is strikingly constant in many species with an intraspecific variable karyotype.
	www.biologie.uni-hamburg.de /b-online/e39/39b.htm (912 words)

	Genetics and Molecular Biology - Heterochromatin analysis in the fish species Liposarcus anisitsi (siluriformes) and ... (Site not responding. Last check: 2007-10-19)
		Constitutive heterochromatin (C-band) was detected according to Sumner (1972), with the following modifications: two-day-old slides were immersed in 0.2 N HCl for 15 min, incubated in 2 x SSC at 60
		B, ZW sex chromosomes showing the great amount of constitutive heterochromatin on their long arm, as well as the correspondence between some heterochromatic segments and positive regions for HSS treatment and mithramycin (MM) staining in the W chromosome.
		Remarkable results refer to the heteromorphic sex chromosomes, where a large amount of heterochromatin was observed on the big long arm of the W chromosome, as well as on some extent of the Z chromosome (Figure 2B).
	www.scielo.br /scielo.php?pid=S1415-47571999000100009&script=sci_arttext&tlng=en (3686 words)

	Garcia
		The chromosomes of Drosophila willistoni were first described by Metz (1916) and later by Dobzhansky (1950) according to whom, this species presents three pairs of mitotic chromosomes, one pair metacentric, one pair acrocentric, and the metacentric sexual pair (X and Y).
		As far as could be seen by C-banding techniques the constitutive heterochromatin in the chromosomes is localised in the centromeric regions of chromosome pairs II and III, and the X- chromosome.
		The Giemsa stained blocks in the pericentromeric region of chromosomes II, III and X disappeared after C-banding, demonstrating that they are not formed from constitutive heterochromatin.
	www.ou.edu /journals/dis/DIS83/Technique83/9tecGarcia/Garcia.htm (920 words)

	Brutlag et al., 1978 (Site not responding. Last check: 2007-10-19)
		Drosophila melanogaster is an ideal organism for the study of the structure and function of heterochromatin because it has only four chromosomes and 25% of its genome is heterochromatic.
		All of the heterochromatin is constitutive and much of it is located in the sex chromosomes, which have been well characterized genetically and cytogenetically (Cooper 1959; Ashburner and Novitski 1976).
		Heterochromatin, therefore, may be dispensable for the survival of a cell or an individual, but it is essential for the survival of a chromosome in the germ line.
	cmgm.stanford.edu /~brutlag/Abstracts/brutlag78.html (475 words)

	Spartanburg SC \| GoUpstate.com \| Spartanburg Herald-Journal
		A chromosome is a single large macromolecule of DNA, and constitutes a physically organized form of DNA in a cell.
		In viruses, mitochondria, and chloroplasts their DNA molecules are commonly referred to as chromosomes, despite being naked molecules, as they constitute the complete genome of the organism or organelle.
		Chromosomes were first observed in plant cells by Swiss botanist Karl Wilhelm von NÃ¤geli in 1842, and independently in Ascaris worms by Belgian scientist Edouard Van Beneden (1846-1910).
	www.goupstate.com /apps/pbcs.dll/section?category=NEWS&template=wiki&text=chromosome (2170 words)

	Survey (Site not responding. Last check: 2007-10-19)
		Constitutive heterochromatin is found primarily near centromeres, is relatively "gene poor", and mostly consists of repetitive DNA sequences.
		One of the most interesting properties of heterochromatin is its ability to silence euchromatic genes if they are brought into juxtaposition with heterochromatin by a chromosomal rearrangement or transposition.
		The inactivation is due to the heterochromatinization of the translocated wild-type locus in some cells.
	genetik.fu-berlin.de /institut/survey.html (584 words)

	Cathepsin L Stabilizes the Histone Modification Landscape on the Y Chromosome and Pericentromeric Heterochromatin -- ...
		Decondensation of constitutive heterochromatin in L cell chromosomes by a benzimidazole compound ("33258 Hoechst").
		Heterochromatin and tri-methylated lysine 20 of histone H4 in animals.
		Histone H3 lysine 9 methylation is an epigenetic imprint of facultative heterochromatin.
	mcb.asm.org /cgi/content/full/26/11/4172 (8114 words)

	The X and Y Chromosomes Assemble into H2A.Z, Containing Facultative Heterochromatin, following Meiosis -- Greaves et ...
		at the pericentric heterochromatin and the Y chromosome in mouse
		heterochromatin is enriched with H4 acetylated at lysine 12
		Heterochromatin, HP1, and methylation at lysine 9 of histone H3 in animals.
	mcb.asm.org /cgi/content/full/26/14/5394 (5591 words)

	Cell nucleus - Psychology Wiki
		Euchromatin is the least compact form of DNA, and the regions of DNA which constitute euchromatin contain genes which are frequently expressed by the cell.
		Regions of DNA which constitute heterochromatin generally contain genes which are not expressed by the cell (this type of heterochromatin is known as facultative heterochromatin) or are regions which make up the telomeres and centromeres of the chromosomes (this type of heterochromatin is known as constitutive heterochromatin).
		Therefore, the regions of DNA that constitute heterochromatin vary between cell types.
	psychology.wikia.com /wiki/Cell_nucleus (578 words)

	Lecture Notes, Genetics, Emporia State Univ.
		heterochromatin remains coiled or condensed during interphase and is replicated late during the S phase.
		facultative heterochromatin - this heterochromatin may revert to euchromatin depending upon the physiological or developmental conditions of the cell.
		The centromeric region is constitutive heterochromatin, but there may be other regions as well.
	www.emporia.edu /biosci/genetics/note46.htm (1931 words)

	BioMed Central \| Full text \| The evolution of the histone methyltransferase gene Su(var)3-9in metazoans includes a ...
		Heterochromatin typically represents a large differentiated chromatin compartment within eukaryotic nuclei (reviewed in [1]).
		While the mechanisms involved in molecular definition of facultative heterochromatin seem diverse [2,3], the central role of histone H3 lysine 9 di- and trimethylation (H3K9me2 and H3K9me3) for the establishment of constitutive heterochromatin and heterochromatic gene silencing has been shown for Drosophila, Schizosaccharomyces and Arabidopsis [4-7].
		Whether Su(var)3-9 proteins are involved in the establishment of heterochromatic regions in aphid chromosomes, which are mostly limited to telomeres and X chromosomes ([42], and references therein), remains to be seen.
	www.biomedcentral.com /1471-2148/6/18 (6537 words)

	High- and Low-mobility Populations of HP1 in Heterochromatin of Mammalian Cells -- Schmiedeberg et al. 15 (6): 2819 -- ...
		Quantitative FRAP analysis for all HP1 isoforms was performed in euchromatin (B), and heterochromatin (C).
		of a subfraction of GFP-HP1 molecules in heterochromatin.
		In addition, there is a minor fraction of very slow HP1 molecules of 5–7% present in constitutive heterochromatin.
	www.molbiolcell.org /cgi/content/full/15/6/2819 (6403 words)

	Composition of constitutive heterochromatin of Pseudonannolene strinatii Mauriès, 1974 (Diplopoda, ...
		Composition of constitutive heterochromatin of Pseudonannolene strinatii Mauriès, 1974 (Diplopoda, Spirostreptida) analyzed by AT/CG specific fluorochromes
		Triple staining with fluorochromes (DA/DAPI/CMA) and C-banding were used to characterize the composition of Pseudonannolene strinatii heterochromatin.
		Fluorochrome staining revealed DAPI+ regions corresponding to the C-banding pattern, indicating that the heterochromatin of this species is abundant in AT-rich sequences.
	www.funpecrp.com.br /gmr/year2005/vol4-4/gmr0141_abstract.htm (87 words)

	[No title]
		Constitutive heterochromatin -- always heterochromatic (ex: chromatin at centromeres, telomeres).
		Facultative heterochromatin-- sometimes heterochromatic in interphase, sometimes not (depends on tissue, time etc.).
		Note: Most of the DNA that is inactive during interphase (in a particular cell type) is NOT heterochromatic.
	www.columbia.edu /cu/biology/courses/c2006/lectures06/lect9.06.html (2272 words)

	Regulated recruitment of HP1 to a euchromatic gene induces mitotically heritable, epigenetic gene silencing: a ...
		Hwang, K.K., Eissenberg, J.C., and Worman, H.J. Transcriptional repression of euchromatic genes by Drosophila heterochromatin protein 1 and histone modifiers.
		James, T.C. and Elgin, S.C. Identification of a nonhistone chromosomal protein associated with heterochromatin in Drosophila melanogaster and its gene.
		Minc, E., Courvalin, J.C., and Buendia, B. HP1gamma associates with euchromatin and heterochromatin in mammalian nuclei and chromosomes.
	www.genesdev.org /cgi/content/full/17/15/1855 (6957 words)

	ZFIN ZF Monitor Vol 3(5) (Site not responding. Last check: 2007-10-19)
		The chromosome complement of Danio rerio was investigated by Giemsa staining, C- banding (for constitutive heterochromatin), Ag- NOR (silver staining of Nucleolus Organizer Regions), and replication banding (BrdU incorporation in late replicating regions).
		Given the similarity in size and morphology of most zebrafish chromosomes, only three chromosome pairs were unequivocally distinguished after Giemsa staining: the two metacentric pairs (6 and 11) and pair 1, the largest of the complement.
		Constitutive heterochromatin as demonstrated by C- banding was located at centromeric position of all chomosome pairs.
	zfin.org /zf_info/monitor/vol3.5/9.html (180 words)

	Role of the RB1 family in stabilizing histone methylation at constitutive heterochromatin - Nature Cell Biology
		Role of the RB1 family in stabilizing histone methylation at constitutive heterochromatin
		Mouse embryonic fibroblasts that are triply deficient for RB1 (retinoblastoma 1), RBL1 (retinoblastoma-like 1) and RBL2 (retinoblastoma-like 2) — known as TKO cells — show a marked genomic instability, which is coincidental with decreased DNA methylation, increased acetylation of histone H3 and decreased tri-methylation of histone H4 at lysine 20 (H4K20).
		These observations indicate that the RB1 family is involved in maintaining overall chromatin structure and, in particular, that of constitutive heterochromatin, linking tumour suppression and the epigenetic definition of chromatin.
	www.nature.com /doifinder/10.1038/ncb1235 (344 words)

	FEBS Abstract
		Trimethylation of H4-K20 in heterochromatin depends on H3-K9 methylation by SU(VAR)3-9 and is catalysed by the SUV4-20 HMTase.
		Notably, a hypermorphic Su(var)3-9 mutant displays extensive H3-K9 di- and trimethylation also outside constitutive heterochromatin and causes ectopic heterochromatization and gene silencing.
		These mutants indicate a general effect of JIL-1 in controlling heterochromatin expansion and provide evidence for dynamic regulation of the balance between heterochromatin and euchromatin.
	www.blackwellpublishing.com /febsabstracts2005/abstract.asp?id=40988 (319 words)

	Dynamic relocation of epigenetic chromatin markers reveals an active role of constitutive heterochromatin in the ...
		Constitutive heterochromatin is a class of compact chromatin
		to regions of constitutive heterochromatin tend to be downregulated
		Horsley, D., Hutchings, A., Butcher, G. and Singh, P. M32, a murine homologue of Drosophila heterochromatin protein 1 (HP1), localizes to euchromatin within interphase nuclei and is largely excluded from constitutive heterochromatin.
	jcs.biologists.org /cgi/content/full/117/25/6153 (5896 words)

	A glue for heterochromatin maintenance: stable SUV39H1 binding to heterochromatin is reinforced by the SET domain -- ...
		Heterochromatin is considered to be the part of the genome that
		the nucleus that corresponded to heterochromatin and euchromatin,
		Higher-order structure in pericentric heterochromatin involves a distinct pattern of histone modification and an RNA component.
	www.jcb.org /cgi/content/full/170/4/537 (6869 words)

	National Academy of Sciences: Sackler Colloquium
		Heterochromatin assembly at the centromeres facilitates proper segregation of chromosomes, and the formation of specialized chromatin structures at telomeres serves to maintain the length of telomeric repeats as well as suppress recombination.
		By using fission yeast as a model system, we previously defined precise sequence of events during heterochromatin assembly and showed that formation of constitutive heterochromatin involves an orchestrated event of histone modifications including histone deacetylation, histone methylation and recruitment of heterochromatin protein Swi6/HP1, which is conserved in higher eukaryotes.
		We find that centromeric repeat sequences and RNAi cooperate to nucleate heterochromatin, which then spreads to neighboring sequences in Swi6/HP1-dpendent manner, leading to silencing of nearby genes.
	www.nasonline.org /site/PageServer?pagename=SACKLER_rnai_grewal (312 words)

	RNAi-Independent Heterochromatin Nucleation by the Stress-Activated ATF/CREB Family Proteins -- Jia et al. 304 (5679): ...
		The assembly and maintenance of heterochromatin initiated by transgene repeats are independent of the RNA interference pathway in Mammalian cells..
		Differential Effects of Heterochromatin Protein 1 Isoforms on Mitotic Chromosome Distribution and Growth in Dictyostelium discoideum.
		Evolutionary-conserved telomere-linked helicase genes of fission yeast are repressed by silencing factors, RNAi components and the telomere-binding protein Taz1.
	www.sciencemag.org /cgi/content/abstract/304/5679/1971 (608 words)

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