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1.
Emerging connections between DNA methylation and histone acetylation 总被引:18,自引:0,他引:18
Modifications of both DNA and chromatin can affect gene expression and lead to gene silencing. Evidence of links between
DNA methylation and histone hypoacetylation is accumulating. Several proteins that specifically bind to methylated DNA are
associated with complexes that include histone deacetylases (HDACs). In addition, DNA methyltransferases of mammals appear
to interact with HDACs. Experiments with animal cells have shown that HDACs are responsible for part of the repressive effect
of DNA methylation. Evidence was found in Neurospora that protein acetylation can in some cases affect DNA methylation. The available data suggest that the roles of DNA methylation
and histone hypoacetylation, and their relationship with each other, can vary, even within an organism. Some open questions
in this emerging field that should be answered in the near future are discussed. 相似文献
2.
Albert-Weissenberger C Cazalet C Buchrieser C 《Cellular and molecular life sciences : CMLS》2007,64(4):432-448
The bacterial pathogen Legionella pneumophila is found ubiquitously in fresh water environments where it replicates within protozoan hosts. When inhaled by humans it can
replicate within alveolar macrophages and cause a severe pneumonia, Legionnaires disease. Yet much needs to be learned regarding
the mechanisms that allow Legionella to modulate host functions to its advantage and the regulatory network governing its intracellular life cycle. The establishment
and publication of the complete genome sequences of three clinical L. pneumophila isolates paved the way for major breakthroughs in understanding the biology of L. pneumophila. Based on sequence analysis many new putative virulence factors have been identified foremost among them eukaryotic-like
proteins that may be implicated in many different steps of the Legionella life cycle. This review summarizes what is currently known about regulation of the Legionella life cycle and gives insight in the Legionella-specific features as deduced from genome analysis.
Received 1 September 2006; received after revision 10 October 2006; accepted 22 November 2006 相似文献
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T. Winckler 《Cellular and molecular life sciences : CMLS》1998,54(5):383-393
Repetitive DNA is a major component of any living cell. In eukaryotes retrotransposable elements make up several percent
of the genome size, and consequently, retroelements are often identified in experiments aimed at establishing physical maps
and whole genome sequences. In this review, recent progress in the characterization of retrotransposable elements in the genome
of the eukaryotic mi croorganism Dictyostelium discoideum is summarized with a focus on retroelements which integrate near transfer RNA genes with intriguing position specificity.
Received 21 November 1997; received after revision 6 January 1998; accepted 6 January 1998 相似文献
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Site- and state-specific lysine methylation of histones is catalyzed by a family of proteins that contain the evolutionarily
conserved SET domain and plays a fundamental role in epigenetic regulation of gene activation and silencing in all eukaryotes.
The recently determined three-dimensional structures of the SET domains from chromosomal proteins reveal that the core SET
domain structure contains a two-domain architecture, consisting of a conserved anti-parallel β-barrel and a structurally variable
insert that surround a unusual knot-like structure that comprises the enzyme active site. These structures of the SET domains,
either in the free state or when bound to cofactor S-adenosyl-L-homocysteine and/or histone peptide, mimicking an enzyme/cofactor/substrate complex, further yield the structural insights
into the molecular basis of the substrate specificity, methylation multiplicity and the catalytic mechanism of histone lysine
methylation.
Received 10 June 2006; accepted 22 August 2006 相似文献
7.
Epigenetic mechanisms in mammals 总被引:11,自引:1,他引:10
DNA and histone methylation are linked and subjected to mitotic inheritance in mammals. Yet how methylation is propagated
and maintained between successive cell divisions is not fully understood. A series of enzyme families that can add methylation
marks to cytosine nucleobases, and lysine and arginine amino acid residues has been discovered. Apart from methyltransferases,
there are also histone modification enzymes and accessory proteins, which can facilitate and/or target epigenetic marks. Several
lysine and arginine demethylases have been discovered recently, and the presence of an active DNA demethylase is speculated
in mammalian cells. A mammalian methyl DNA binding protein MBD2 and de novo DNA methyltransferase DNMT3A and DNMT3B are shown experimentally to possess DNA demethylase activity. Thus, complex mammalian
epigenetic mechanisms appear to be dynamic yet reversible along with a well-choreographed set of events that take place during
mammalian development. 相似文献
8.
Heras SR Thomas MC García-Canadas M de Felipe P García-Pérez JL Ryan MD López MC 《Cellular and molecular life sciences : CMLS》2006,63(12):1449-1460
A comparative analysis of 40 Trypanosoma cruzi L1Tc elements showed that the 2A self-cleaving sequence described in viruses is present in them. Of these elements, 72% maintain
the canonical 2A motif (DxExNPGP). A high percentage has a conserved point mutation within the motif that has not been previously
described. In vitro and in vivo expression of reporter polyproteins showed that the L1Tc2A sequence is functional. Mutations within certain L1Tc2A sequences
affect the efficiency of the cleavage. The data indicate that the L1Tc2A sequence may be influencing the L1Tc enzymatic machinery
determining the composition and level of the translated products. The residues located immediately upstream of the 2A consensus
sequence increase the cleaving efficiency and appear to stabilize the relative amount of translated products.
These authors contributed equally to this work.
Received 26 January 2006; received after revision 11 April 2006; accepted 21 April 2006 相似文献
9.
Summary Adult chicken brain DNA is subject to a developmental alteration of methylation atHpaII sites flanking 4, 1, 0.8 and 0.7 kilobase sequences. This change is not evident in adult chicken liver DNA and 1-day-old chick brain and liver DNAs, suggesting tissue specificity and age-dependency in DNA methylation. 相似文献
10.
Summary A dedifferentiating system in plant tissue (Nicotiana glauca pith tissue grown in vitro) is described, where DNA amplification was demonstrated both cytologically and biochemically. In this system a DNA statellite is synthesized and reaches its maximum around 48 h of culture. This satellite is highly methylated and there are 2 methylation and there are 2 methylation peaks around 24 and 72 h of culture. The results are discussed in relation to recent evidence of the involvement of methylation in differentiation processes. 相似文献
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Complex diseases arise from a combination of heritable and environmental factors. The contribution made by environmental factors
may be mediated through epigenetics. Epigenetics is the study of changes in gene expression that occur without a change in
DNA sequence and are meiotically or mitotically heritable. Such changes in gene expression are achieved through the methylation
of DNA, the post-translational modifications of histone proteins, and RNA-based silencing. Epigenetics has been implicated
in complex diseases such as cancer, schizophrenia, bipolar disorder, autism and systemic lupus erythematosus. The prevalence
and severity of these diseases may be influenced by factors that affect the epigenotype, such as ageing, folate status, in vitro fertilization and our ancestors’ lifestyles. Although our understanding of the role played by epigenetics in complex diseases
remains in its infancy, it has already led to the development of novel diagnostic methods and treatments, which augurs well
for its future health benefits.
Received 6 December 2006; received after revision 29 January 2007; accepted 15 March 2007 相似文献
13.
Structure,function and evolution of CpG island promoters 总被引:23,自引:0,他引:23
Antequera F 《Cellular and molecular life sciences : CMLS》2003,60(8):1647-1658
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DNA from 30-million-year-old amber preserved termites (Mastotermes electrodominicus) was PCR amplified with nuclear ribosomal RNA small subunit primers and cloned into the TA vector (INVITROGEN). We obtained several classes of recombinant clones as a result. AuthenticMastotermes electrodominicus clones were identified. The source of other classes of clones was identified as contaminants of the ancient DNA template. Several of the clones appeared to be chimeric in structure with half of the clone identical to the termite sequence and the other half identical to contaminant sequences. The phenomenon of PCR jumping was identified as a possible source for the chimeric clones. 相似文献
16.
B. M. Stringer J. M. Rowson M. H. Parkar J. M. Seid P. R. Hearn D. Wynford-Thomas S. Ingemansson N. Woodhouse Dr. M. H. Goyns 《Cellular and molecular life sciences : CMLS》1989,45(4):372-376
Summary We have transfected high-molecular-weight DNA from human thyroid carcinomas into murine 3T3 cells. As a result we identified several foci of morphologically distinct transformed cells in each of the tumour DNA transfected cultures. After a total of three rounds of transfection, the transformed cells were shown to form tumours in nude mice. Southern blot analysis of DNA prepared from third-round transfectants demonstrated the presence of human Alu repetitive sequences and, after hybridization with probes for known oncogenes, indicated the presence of the humanH-RAS oncogene in 3T3 cells transfected with three out of four anaplastic carcinoma DNA samples. It appears therefore that activation ofRAS genes may be an important event in the development of the anaplastic thyroid tumours. 相似文献
17.
Comparison of SXT and R391, two conjugative integrating elements: definition of a genetic backbone for the mobilization of resistance determinants 总被引:10,自引:0,他引:10
Beaber JW Burrus V Hochhut B Waldor MK 《Cellular and molecular life sciences : CMLS》2002,59(12):2065-2070
The SXT element (SXT) is becoming an increasingly prevalent vector for the dissemination of antibiotic resistances in Vibrio cholerae. SXT is a member of a larger family of elements, formerly defined as IncJ plasmids, that are self-transmissible by conjugation
and integrate site-specifically into the host chromosome. Comparison of the DNA sequences of SXT and R391, an IncJ element
from Providencia rettgeri, indicate that these elements consist of a conserved backbone that mediates the regulation, excision/integration and conjugative
transfer of the elements. Both elements have insertions into this backbone that either confer the element-specific properties
or are of unknown function. Interestingly, the conserved SXT and R391 backbone apparently contains hotspots for insertion
of additional DNA sequences. This backbone represents a scaffold for the mobilization of genetic material between a wide range
of Gram-negative bacteria, allowing for rapid adaptation to changing envi
ronments.
RID="*"
ID="*"Corresponding author. 相似文献
18.
I. Dufournel M. P. Garcia Guerreiro C. Arnault C. Biémont 《Cellular and molecular life sciences : CMLS》1994,50(2):164-166
A highly inbred line ofDrosophila melanogaster, stable for the insertion pattern of the transposable elements copia and mdg1, was experimentally contaminated by flies from another line. We show that the alien genome income is clearly detectable by the changes induced in the insertion profiles of transposable elements, even twenty generations later. 相似文献
19.
DNA transposons in vertebrate functional genomics 总被引:7,自引:0,他引:7
Miskey C Izsvák Z Kawakami K Ivics Z 《Cellular and molecular life sciences : CMLS》2005,62(6):629-641
Genome sequences of many model organisms of developmental or agricultural importance are becoming available. The tremendous amount of sequence data is fuelling the next phases of challenging research: annotating all genes with functional information, and devising new ways for the experimental manipulation of vertebrate genomes. Transposable elements are known to be efficient carriers of foreign DNA into cells. Notably, members of the Tc1/mariner and the hAT transposon families retain their high transpositional activities in species other than their hosts. Indeed, several of these elements have been successfully used for transgenesis and insertional mutagenesis, expanding our abilities in genome manipulations in vertebrate model organisms. Transposon-based genetic tools can help scientists to understand mechanisms of embryonic development and pathogenesis, and will likely contribute to successful human gene therapy. We discuss the possibilities of transposon-based techniques in functional genomics, and review the latest results achieved by the most active DNA transposons in vertebrates. We put emphasis on the evolution and regulation of members of the best-characterized and most widely used Tc1/mariner family.Received 8 June 2004; received after revision 26 October 2004; accepted 18 November 2004 相似文献