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1.
Escribá MC Greciano PG Méndez-Lago M de Pablos B Trifonov VA Ferguson-Smith MA Goday C Villasante A 《Chromosoma》2011,120(4):387-397
Sciara coprophila (Diptera, Nematocera) constitutes a classic model to analyze unusual chromosome behavior such as the somatic elimination
of paternal X chromosomes, the elimination of the whole paternal, plus non-disjunction of the maternal X chromosome at male
meiosis. The molecular organization of the heterochromatin in S. coprophila is mostly unknown except for the ribosomal DNA located in the X chromosome pericentromeric heterochromatin. The characterization
of the centromeric regions, thus, is an essential and required step for the establishment of S. coprophila as a model system to study fundamental mechanisms of chromosome segregation. To accomplish such a study, heterochromatic
sections of the X chromosome centromeric region from salivary glands polytene chromosomes were microdissected and microcloned.
Here, we report the identification and characterization of two tandem repeated DNA sequences from the pericentromeric region
of the X chromosome, a pericentromeric RTE element and an AT-rich centromeric satellite. These sequences will be important
tools for the cloning of S. coprophila centromeric heterochromatin using libraries of large genomic clones. 相似文献
2.
Summary
Rumex acetosa (sorrel) is a dioecious plant with a XX/XY1Y2 sex chromosome system. Both the Y chromosomes are nearly entirely heterochromatic and it has been hypothesised that they can persist as chromocenters in male interphase nuclei. Using specific antibodies against 5-methylcytosine and histone H4 acetylated at terminal lysine 5, global levels of DNA methylation and histone acetylation were studied on the sex chromosomes and autosomes of both sexes. The heterochromatic Y chromosomes did not display a higher methylation level compared to the autosomes. The only prominent hypermethylation signals were found at two nucleolar organising regions located on the autosome pair V, as confirmed by in situ hybridisation with 25S rDNA probe and staining. Immunoanalysis of DNA methylation on female and male interphase nuclei neither revealed any sex-specific differences. Two active (silverpositive) nucleoli and two likely inactive nucleolar organising regions (displaying prominent methylation signals) were found in both sexes. In a fraction of nuclei isolated from leaf cells, two peripheral bodies strongly positive for 4,6-diamidino-2-phenylindole were observed only in males, never in females. These heterochromatin regions were depleted in histone H4 acetylation at terminal lysine 5 and corresponded, according to in situ hybridisation with a Y-chromosome-specific repetitive probe, to the two Y chromosomes. We conclude that the peripheral condensed bodies observed exclusively in male nuclei represent the constitutive heterochromatin of the Y chromosomes which is characterised by a substantial histone H4 underacetylation. 相似文献
3.
Assembly and characterization of heterochromatin and euchromatin on human artificial chromosomes 下载免费PDF全文
Background
Human centromere regions are characterized by the presence of alpha-satellite DNA, replication late in S phase and a heterochromatic appearance. Recent models propose that the centromere is organized into conserved chromatin domains in which chromatin containing CenH3 (centromere-specific H3 variant) at the functional centromere (kinetochore) forms within regions of heterochromatin. To address these models, we assayed formation of heterochromatin and euchromatin on de novo human artificial chromosomes containing alpha-satellite DNA. We also examined the relationship between chromatin composition and replication timing of artificial chromosomes.Results
Heterochromatin factors (histone H3 lysine 9 methylation and HP1α) were enriched on artificial chromosomes estimated to be larger than 3 Mb in size but depleted on those smaller than 3 Mb. All artificial chromosomes assembled markers of euchromatin (histone H3 lysine 4 methylation), which may partly reflect marker-gene expression. Replication timing studies revealed that the replication timing of artificial chromosomes was heterogeneous. Heterochromatin-depleted artificial chromosomes replicated in early S phase whereas heterochromatin-enriched artificial chromosomes replicated in mid to late S phase.Conclusions
Centromere regions on human artificial chromosomes and host chromosomes have similar amounts of CenH3 but exhibit highly varying degrees of heterochromatin, suggesting that only a small amount of heterochromatin may be required for centromere function. The formation of euchromatin on all artificial chromosomes demonstrates that they can provide a chromosome context suitable for gene expression. The earlier replication of the heterochromatin-depleted artificial chromosomes suggests that replication late in S phase is not a requirement for centromere function.4.
Zakrzewski F Weisshaar B Fuchs J Bannack E Minoche AE Dohm JC Himmelbauer H Schmidt T 《Chromosoma》2011,120(4):409-422
Sugar beet (Beta vulgaris) chromosomes consist of large heterochromatic blocks in pericentromeric, centromeric, and intercalary regions comprised of
two different highly abundant DNA satellite families. To investigate DNA methylation at single base resolution at heterochromatic
regions, we applied a method for strand-specific bisulfite sequencing of more than 1,000 satellite monomers followed by statistical
analyses. As a result, we uncovered diversity in the distribution of different methylation patterns in both satellite families.
Heavily methylated CG and CHG (H=A, T, or C) sites occur more frequently in intercalary heterochromatin, while CHH sites,
with the exception of CAA, are only sparsely methylated, in both intercalary and pericentromeric/centromeric heterochromatin.
We show that the difference in DNA methylation intensity is correlated to unequal distribution of heterochromatic histone
H3 methylation marks. While clusters of H3K9me2 were absent from pericentromeric heterochromatin and restricted only to intercalary
heterochromatic regions, H3K9me1 and H3K27me1 were observed in all types of heterochromatin. By sequencing of a small RNA
library consisting of 6.76 million small RNAs, we identified small interfering RNAs (siRNAs) of 24 nucleotides in size which
originated from both strands of the satellite DNAs. We hypothesize an involvement of these siRNAs in the regulation of DNA
and histone methylation for maintaining heterochromatin. 相似文献
5.
Chromatin organization in the holocentric chromosomes of the green apple aphid Aphis pomi has been investigated at a cytological level after C-banding, NOR, Giemsa, fluorochrome staining and fluorescent in situ hybridization (FISH). C-banding technique showed that heterochromatic bands are exclusively located on X chromosomes. This data represents a peculiar feature that clearly contradicts the equilocal distribution of heterochromatin typical of monocentric chromosomes. Moreover, silver staining and FISH carried out with a 28S rDNA probe localized rDNA genes on one telomere of each X chromosome; CMA3 staining reveals that these silver positive telomeres are the only GC-rich regions among A. pomi heterochromatin, whereas all other C-positive bands are DAPI positive thus containing AT-rich DNA. 相似文献
6.
Jiří Bu Irma Ebert Monica Ruffini-Castiglione Jiří Široký Boris Vyskot Johann Greilhuber 《Planta》1998,204(4):506-514
Pentaploid endosperm nuclei in certain Gagea species exhibit large masses of sticky and dense chromatin, not observed in somatic nuclei. These heterochromatin masses
most probably stem from the triploid chalasal polar nucleus of the embryo sac, thus representing an example of facultative
heterochromatinisation in plants. In the present investigation, we studied the nuclei in Gagea lutea (L.) Ker-Gawl. endosperm tissue. The position of the heterochromatin in interphase nuclei was observed by confocal laser scanning
microscopy (CLSM) and the DNA methylation status of the euchromatin and heterochromatin was analysed by immunolabelling with
an antibody raised against 5-methylcytosine (anti-5-mC). In young endosperms, heterochromatin was relatively dispersed, occupying
some peripheral and inner parts of the nuclei. In a later endosperm development, the nuclei became smaller and more pycnotic,
and the heterochromatin masses were placed predominantly near the nuclear periphery. The distribution of anti-5-mC labelling
on the heterochromatic regions was unequal: some parts appeared hypermethylated while other parts were, like the euchromatin,
not labelled. During mitosis, the labelling intensity of all the chromosomes was approximately the same, thus indicating that
there are no cytologically detectable methylation differences among the individual sets of chromosomes. However, differences
in the anti-5-mC signal intensity along individual chromosomes were observed, resulting in banding patterns with highly positive
bands apparently representing constitutive heterochromatic regions. From these results it is obvious that facultative heterochromatinisation,
in contrast to constitutive heterochromatinisation, need not be strictly accompanied by a prominent DNA hypermethylation.
Received: 24 April 1997 / Accepted: 28 July 1997 相似文献
7.
Eukaryotic chromosomes are organized into two large and distinct domains, euchromatin and heterochromatin, which are cytologically
characterized by different degrees of chromatin compaction during interphase/prophase and by post-synthesis modifications
of histones and DNA methylation. Typically, heterochromatin remains condensed during the entire cell cycle whereas euchromatin
is decondensed at interphase. However, a fraction of the euchromatin can also remain condensed during interphase and appears
as early condensing prophase chromatin. 5S and 45S rDNA sites and telomere DNA were used to characterize these regions in
metaphase and interphase nuclei. We investigated the chromosomal distribution of modified histones and methylated DNA in the
early and late condensing prophase chromatin of two species with clear differentiation between these domains. Both species,
Costus spiralis and Eleutherine bulbosa, additionally have a small amount of classical heterochromatin detected by CMA/DAPI staining. The distribution of H4 acetylated
at lysine 5 (H4K5ac), H3 phosphorylated at serine 10 (H3S10ph), H3 dimethylated at lysine 4 or 9 (H3K4me2, H3K9me2), and 5-methylcytosine
was compared in metaphase, prophase, and interphase cells by immunostaining with specific antibodies. In both species, the
late condensing prophase chromatin was highly enriched in H4K5ac and H3K4me2 whereas the early condensing chromatin was very
poor in these marks. H3K9me2 was apparently uniformly distributed along the chromosomes whereas the early condensing chromatin
was slightly enriched in 5-methylcytosine. Signals of H3S10ph were restricted to the pericentromeric region of all chromosomes.
Notably, none of these marks distinguished classical heterochromatin from the early condensing euchromatin. It is suggested
that the early condensing chromatin is an intermediate type between classical heterochromatin and euchromatin. 相似文献
8.
Tandem repetitive sequences are DNA motifs common in the genomes of eukaryotic species and are often embedded in heterochromatic regions. In most eukaryotes, ribosomal genes, as well as centromeres and telomeres or subtelomeres, are associated with abundant tandem arrays of repetitive sequences and typically represent the final barriers to completion of whole-genome sequencing. The nature of these repeats makes it difficult to estimate their actual sizes. In this study, combining the two cytological techniques DNA fiber-FISH and pachytene chromosome FISH allowed us to characterize the tandem repeats distributed genome wide in Antirrhinum majus and identify four types of tandem repeats, 45S rDNA, 5S rDNA, CentA1, and CentA2, representing the major tandem repetitive components, which were estimated to have a total length of 18.50 Mb and account for 3.59% of the A. majus genome. FISH examination revealed that all the tandem repeats correspond to heterochromatic knobs along the pachytene chromosomes. Moreover, the methylation status of the tandem repeats was investigated in both somatic cells and pollen mother cells from anther tissues using an antibody against 5-methylcytosine combined with sequential FISH analyses. Our results showed that these repeats were hypomethylated in anther tissues, especially in the pollen mother cells at pachytene stage. 相似文献
9.
Claudia Baumann Anja Schmidtmann Kathrin Muegge Rabindranath De La Fuente 《BMC molecular biology》2008,9(1):29
Background
Establishment of chromosomal cytosine methylation and histone methylation patterns are critical epigenetic modifications required for heterochromatin formation in the mammalian genome. However, the nature of the primary signal(s) targeting DNA methylation at specific genomic regions is not clear. Notably, whether histone methylation and/or chromatin remodeling proteins play a role in the establishment of DNA methylation during gametogenesis is not known. The chromosomes of mouse neonatal spermatogonia display a unique pattern of 5-methyl cytosine staining whereby centromeric heterochromatin is hypo-methylated whereas chromatids are strongly methylated. Thus, in order to gain some insight into the relationship between global DNA and histone methylation in the germ line we have used neonatal spermatogonia as a model to determine whether these unique chromosomal DNA methylation patterns are also reflected by concomitant changes in histone methylation. 相似文献10.
Veiko Krauss Anne Fassl Petra Fiebig Ina Patties Heinz Sass 《BMC evolutionary biology》2006,6(1):18-15
Background
In eukaryotes, histone H3 lysine 9 (H3K9) methylation is a common mechanism involved in gene silencing and the establishment of heterochromatin. The loci of the major heterochromatic H3K9 methyltransferase Su(var)3-9 and the functionally unrelated γ subunit of the translation initiation factor eIF2 are fused in Drosophila melanogaster. Here we examined the phylogenetic distribution of this unusual gene fusion and the molecular evolution of the H3K9 HMTase Su(var)3-9. 相似文献11.
Diogo Cavalcanti Cabral-de-Mello Rita de Cássia de Moura Maria José de Souza 《Genetica》2010,138(2):191-195
12.
13.
The chromosomes of Parascaris univalens possess a continuous centromeric structure spanning their entire length in gonial cells. A cytological and ultrastructural analysis of P. univalens meiotic chromosomes was performed. The results show that during meiosis the holocentric germline chromosomes of male P. univalens undergo restriction of kinetic activity to the heterochromatic terminal regions. These regions lack kinetochore structures and interact directly with spindle microtubules. 相似文献
14.
DNA methylation controls histone H3 lysine 9 methylation and heterochromatin assembly in Arabidopsis 总被引:10,自引:0,他引:10 下载免费PDF全文
Soppe WJ Jasencakova Z Houben A Kakutani T Meister A Huang MS Jacobsen SE Schubert I Fransz PF 《The EMBO journal》2002,21(23):6549-6559
We propose a model for heterochromatin assembly that links DNA methylation with histone methylation and DNA replication. The hypomethylated Arabidopsis mutants ddm1 and met1 were used to investigate the relationship between DNA methylation and chromatin organization. Both mutants show a reduction of heterochromatin due to dispersion of pericentromeric low-copy sequences away from heterochromatic chromocenters. DDM1 and MET1 control heterochromatin assembly at chromocenters by their influence on DNA maintenance (CpG) methylation and subsequent methylation of histone H3 lysine 9. In addition, DDM1 is required for deacetylation of histone H4 lysine 16. Analysis of F(1) hybrids between wild-type and hypomethylated mutants revealed that DNA methylation is epigenetically inherited and represents the genomic imprint that is required to maintain pericentromeric heterochromatin. 相似文献
15.
The centromeric region of Costus spiralis is characteristically composed of a small heterochromatic DAPI(+) band flanked by a discrete decondensed region. High concentrations of serine 10 of histone H3 (H3S10ph) around the DAPI(+) band in pachytene chromosomes and the location of this heterochromatin at the chromosome region directed towards the poles during metaphase-anaphase I confirm its integration into the centromeric region. Antibodies against both typical components of euchromatin histones (histone H4 acetylated at lysine 5 (H4K5ac) and histone H3 dimethylated at lysine 4 (H3K4me2)) and heterochromatin (dimethylated lysine 9 of H3 (H3K9me2) and anti-5-methylcytosine (5-mC)) were used to characterize the centromeric chromatin of this species during meiosis. In pachytene chromosomes, the decondensed terminal euchromatin of the chromosome arms were seen to be richer in H4K5ac and H3K4me2 histones, while the more condensed proximal region was relatively stronger labeled with anti-H3K9me2 and anti-5-methylcytosine (5-mC). The centromeric region itself, including the DAPI(+) band, was poor in all of these chromatin modifications, but it was highly enriched in H4K5ac at pachytene. Before and after this stage, the centromeric region was poorly labeled with anti-H4K5ac. Hypomethylation and hyperacetylation of any kind of heterochromatin has rarely been reported, and it may be related to the dominant role of the centromere domain over the heterochromatin repeats. 相似文献
16.
17.
There are few examples of differentiated sex chromosomes in fishes. In the genus Leporinus, seven species present a highly differentiated ZW system, derived from heterochromatinization process. Cytogenetic analyses
carried out in three of these fish species, Leporinus obtusidens, L. elongatus and L. reinhardti, through RBG-banding, showed late replication bands, coincident with heterochromatic regions in both Z and W chromosomes.
A similar interstitial early replication segment was observed in the complex heterochromatic region along the Wq arms in the
three species, which might correspond to a pseudoautosomal segment (SD, sex determining locus). Asynchrony related to the
replication pattern among different Z chromosomes was not observed. When the identification of nuclear organizer regions by
silver nitrate was performed over chromosomal preparations previously exposed to 5-bromo-2′-deoxyuridine (BrdU), remarkable
positive signals at interstitial and telomeric position were observed on the q arms of W chromosomes in the species L. elongatus and L. reinhardti. The absence of 18S ribosomal RNA gene loci in this region, formerly demonstrated by FISH, indicates that this argentophilic
behavior is putatively due to heterochromatin decondensation caused by BrdU incorporation, favoring such Ag+ reaction. Early
and late replication bands were also observed in the heterochromatic portions of Z and W chromosomes, indicating that euchromatic
and heterochromatic regions are interspersed. The present data suggest a significant level of heterochromatic complexity in
the sex chromosomes of each species. On the other hand, the replication pattern shared by them supports a monophyletic origin. 相似文献
18.
In Drosophila melanogaster, the two chromosomal proteins HP1 and HP2 colocalize on heterochromatic and euchromatic sites in polytene chromosomes. Mutations
in the HP2 gene act as dominant suppressors of position effect variegation, demonstrating a role for HP2 in the formation
or maintenance of heterochromatin. In this paper, we investigated whether a putative homolog of the D. melanogaster HP2 is involved in the facultative heterochromatinization process in mealybugs. Using an antibody raised against the Drosophila HP2, we identified in the mealybug Planococcus citri a cross-reactive epitope, which we refer to as HP2-like. We investigated the HP2-like pattern during the male embryo development
where the entire paternal haploid chromosome set becomes heterochromatic. The HP2 antibody heavily decorates the chromocenters,
where it localizes with HP1, and marks the chromatin before it acquires the full cytological characteristics of the male-specific
heterochromatin. In euchromatic chromosomes, HP2-like is mainly concentrated at telomeric sites. The interplay between HP2-like
and HP1-like was studied by dsRNA interference experiments. Extinguishing HP1-like expression by RNAi does not prevent the
association of HP2-like with facultative heterochromatin, implying that HP2-like binds to chromatin in a HP1-independent manner.
Our results confirm and extend the structural and functional conservation of proteins involved in heterochromatin assembly.
Silvia Volpi and Silvia Bongiorni contributed equally to the work. 相似文献
19.
Silvia Bongiorni Margherita Pugnali Silvia Volpi Davide Bizzaro Prim B. Singh Giorgio Prantera 《Chromosoma》2009,118(4):501-512
The establishment of sex-specific epigenetic marks during gametogenesis is one of the key feature of genomic imprinting. By
immunocytological analysis, we thoroughly characterized the chromatin remodeling events that take place during gametogenesis
in the mealybug Planococcus citri, in which an entire haploid set of (imprinted) chromosomes undergoes facultative heterochromatinization in male embryos.
Building on our previous work, we have investigated the interplay of several epigenetic marks in the regulation of this genome-wide
phenomenon. We characterized the germline patterns of histone modifications, Me(3)K9H3, Me(2)K9H3, and Me(3)K20H4, and of
heterochromatic proteins, PCHET2 (HP1-like) and HP2-like during male and female gametogenesis. We found that at all stages
in oogenesis chromatin is devoid of any detectable epigenetic marks. On the other hand, spermatogenesis is accompanied by
a complex pattern of redistribution of epigenetic marks from euchromatin to heterochromatin, and vice versa. At the end of
spermatogenesis, sperm heads are decorated by all the molecules we tested, except for PCHET2. However, only Me(3)K9H3 and
Me(2)K9H3 are still detectable in the male pronucleus. We suggest that the histone H3 lysine 9 methylation is the signal used
to establish the male-specific imprinting on the paternal genome, thus allowing it to be distinguished from the maternal genome
in the developing embryo.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
20.
N. L. Bolsheva O. V. Dyachenko T. E. Samatadze O. A. Rachinskaya N. S. Zakharchenko T. V. Shevchuk 《Plant biosystems》2016,150(5):916-922
The karyotype of the common ice plant Mesembryanthemum crystallinum L. (Aizoaceae) was studied using Chromomycin A3 (CMA)/4′,6-diamidino-2-phenylindole (DAPI) staining, fluorescence in situ hybridization with 5S and 18S–5.8S–25S rDNA probes, DAPI/C-banding and immunodetection of 5-methylcytosine. A single bright CMA-band was revealed on the satellite chromosome, whose location was coincided with a position of a site of 18S–5.8S–25S rRNA genes. A site of 5S rRNA genes was observed on one of the other chromosomes. Relatively large DAPI/C-bands were mainly localized in the pericentromeric regions of the chromosomes. DAPI/C-banding patterns allowed us to identify all the chromosomes in the karyotype of M. crystallinum. The methylation of euchromatic chromosome regions was weaker as compared with heterochromatic DAPI/C-bands, which were hypermethylated. The obtained results may provide opportunities for investigating, at the chromosomal level, the genomic changes occurring in M. crystallinum either under salinization or under the action of other stress factors. 相似文献