共查询到20条相似文献,搜索用时 15 毫秒
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It was shown earlier that the Mcp, Fab-7, and Fab-8 boundaries of the bithorax complex contain insulators that effectively block the enhancers of the yellow and white genes. Other boundaries have not been studied so far. The recent mapping of binding sites for the insulator protein dCTCF in the regulatory regions of the bithorax complex genes permitted the Fab-3, Fab-4, and Fab-6 boundaries to be localized. Here, we showed despite the presence of dCTCF-binding sites fragments of the Fab-3, Fab-4, and Fab-6 boundaries do not exhibit the properties of insulators in the model system with the yellow and white genes. Moreover, in some regions of the genome the Fab-4 and Fab-6 boundaries display the properties of silencers. 相似文献
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Polycomb group (PcG) proteins are required to maintain a stable repression of the homeotic genes during Drosophila development. Mutants in the PcG gene Supressor of zeste 12 (Su(z)12) exhibit strong homeotic transformations caused by widespread misexpression of several homeotic genes in embryos and larvae.
Su(z)12 has also been suggested to be involved in position effect variegation and in regulation of the white gene expression in combination with zeste. To elucidate whether SU(Z)12 has any such direct functions we investigated the binding pattern to polytene chromosomes and
compared the localization to other proteins. We found that SU(Z)12 binds to about 90 specific eukaryotic sites, however, not
the white locus. We also find staining at the chromocenter and the nucleolus. The binding along chromosome arms is mostly in interbands
and these sites correlate precisely with those of Enhancer-of-zeste and other components of the PRC2 silencing complex. This
implies that SU(Z)12 mainly exists in complex with PRC2. Comparisons with other PcG protein-binding patterns reveal extensive
overlap. However, SU(Z)12 binding sites and histone 3 trimethylated lysine 27 residues (3meK27 H3) do not correlate that well.
Still, we show that Su(z)12 is essential for tri-methylation of the lysine 27 residue of histone H3 in vivo, and that overexpression of SU(Z)12 in somatic
clones results in higher levels of histone methylation, indicating that SU(Z)12 is rate limiting for the enzymatic activity
of PRC2. In addition, we analyzed the binding pattern of Heterochromatin Protein 1 (HP1) and found that SU(Z)12 and HP1 do
not co-localize. 相似文献
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Gwénaelle Crénès Corinne Moundras Marie-Véronique Demattei Yves Bigot Agnès Petit Sylvaine Renault 《Genetica》2010,138(5):509-517
The eukaryotic transposon Mos1 is a class-II transposable element that moves using a “cut-and-paste” mechanism in which the transposase is the only protein
factor required. The formation of the excision complex is well documented, but the integration step has so far received less
investigation. Like all mariner-like elements, Mos1 was thought to integrate into a TA dinucleotide without displaying any other target selection preferences. We set out to
synthesize what is currently known about Mos1 insertion sites, and to define the characteristics of Mos1 insertion sequences in vitro and in vivo. Statistical analysis can be used to identify the TA dinucleotides that are non-randomly
targeted for transposon integration. In vitro, no specific feature determining target choice other than the requirement for
a TA dinucleotide has been identified. In vivo, data were obtained from two previously reported integration hotspots: the
bacterial cat gene and the Caenorhabditis elegans rDNA locus. Analysis of these insertion sites revealed a preference for TA dinucleotides that are included in TATA or TA × TA
motifs, or located within AT-rich regions. Analysis of the physical properties of sequences obtained in vitro and in vivo
do not help to explain Mos1 integration preferences, suggesting that other characteristics must be involved in Mos1 target choice. 相似文献
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The intron sequence of chloroplast rpS16 and the secondary structure of its pre-mRNA were characterized for the first time in 26 Allium sativum accessions of different ecologo-geographical origins and seven related Allium species. The boundaries and main stem-loop consensus sequences were identified for all six domains of the intron. Polymorphism
was estimated for the total intron and its regions. The structural regions of the rpS16 intron proved to be heterogeneous for mutation rate and spectrum. Mutations were most abundant in domains II and IV, and
transition predominated in domains I, III, V, and VI. In addition to structural elements and motifs typical for group IIB
introns, several Allium-specific micro- and macrostructural mutations were revealed. A 290-bp deletion involving domains III and IV and part of domain
V was observed in A. altaicum, A. fistulosum, and A. schoenoprasum. Several indels and nucleotide substitutions were found to cause a deviation of the pre-mRNA secondary structure from the
consensus model of group II introns. 相似文献
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A. Yu. Chernenkov D. V. Fedorov L. M. Gracheva T. A. Evstuhina S. V. Kovaltsova V. T. Peshekhonov I. V. Fedorova V. G. Korolev 《Russian Journal of Genetics》2012,48(3):284-290
It was assumed previously that the mutator phenotype of the hms3 mutant was determined by processes taking place in the D-loop. As a next step, genetic analysis was performed to study the
interactions between the hsm3 mutation and mutations of the genes that control the initial steps of the D-loop formation. The mutations of the MMS4 and XRS2 genes, which initiate the double-strand break formation and subsequent repair, were shown to completely block HSM3-dependent UV-induced mutagenesis. Mutations of the RAD51, RAD52, and RAD54 genes, which are also involved in the D-loop formation, only slightly decreased the level of UV-induced mutagenesis in the
hsm3 mutant. Similar results were observed for the interaction of hsm3 with the mph1 mutation, which stabilizes the D-loop. In contrast, the shu1 mutation, which destabilizes the D-loop structure, led to an extremely high level of UV-induced mutagenesis and displayed
epistatic interactions with the hsm3 mutation. The results made it possible to assume that the hsm3 mutation destabilizes the D-loop, which is a key substrate of both Rad5- and Rad52-dependent postreplicative repair pathways. 相似文献
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The plasma membrane transport proteins belong to SoLute Carrier 15 (SLC15) family and two members of this family have been
characterized extensively in higher vertebrates, namely PEPT1 and PEPT2. Despite many efforts have made to define a pharmacophore
model for efficient binding and transporting of substrates, there is not a comprehensive study performed to elucidate the
evolutionary mechanisms among the SLC15 family members and to statistically evaluate sequence conservation and functional
divergence between members. In this study, we compared and contrasted the rates and patterns of molecular evolution of 2 PEPT genes. Phylogenetic tree assembly with all available vertebrate PEPTs suggests that the PEPTs originated by duplications and diverged from a common protein at the base of the eukaryotic tree. Topological structure demonstrates
both members share the similar hydrophobic domains (TMDs), which have been constrained by purifying selection. Although both
genes show qualitatively similar patterns, their rates of evolution differ significantly due to an increased rate of synonymous
substitutions in the structural domains in one copy, suggesting substantial differences in functional constraint on each gene.
Site-specific profiles were established by posterior probability analysis revealing significantly divergent regions mainly
locate at the hydrophobic region between predicted transmembrane domains 9 and 10 of the proteins. Thus, these results provide
the evidence that several amino acid residues with reduced selective constraints are largely responsible for functional divergence
between the paralogous PEPTs. These findings may provide a starting point for further experimental verifications. 相似文献
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L. Wanntorp H.-E. Wanntorp B. Oxelman M. Källersjö 《Plant Systematics and Evolution》2001,226(1-2):85-107
The phylogeny of the genus Gunnera is investigated for the first time. Twelve species representing the six currently recognised subgenera are analysed. Two
chloroplast DNA regions, the rbcL gene and the rps16 intron, together provide 46 informative characters out of 2335. A combined analysis of both genes gives four most parsimonious
trees, firmly establishing the east South American G. herteri as sister group to the rest of the genus. The African G. perpensa is sister group to two well-supported clades, one including the South American subgenera Misandra and Panke, the other the Australian/New Zealand/Malayan species of subgenera Milligania and Pseudogunnera. Thus, South America is a composite area for Gunnera, showing up at two different levels in the cladogram. Our analysis supports a close biogeographic relationship between Australia
and New Zealand. The evolution of some morphological characters is discussed. Lastly, the unusual structure of some of the
rbcL sequences is reported.
Received July 6, 2000 Accepted October 24, 2000 相似文献
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Within eukaryotes, tolerance to DNA damage is determined primarily by the repair pathway controlled by the members of the
RAD6 epistasis group. Genetic studies on a yeast Saccharomyces cerevisiae model showed that the initial stage of postreplication repair (PRR), i.e., initiation of replication through DNA damage,
is controlled by Rad6–Rad18 ubiquitin-conjugating enzyme complex. Mutants of these genes are highly sensitive to various genotoxic
agents and reduce the level of induced mutagenesis. In this case, the efficiency of mutagenesis suppression depends on the
type of damage. In this study we showed that DNA damage induced by hydrogen peroxide at the same mutagen doses causes significantly
more mutations and lethal events in the rad18 mutant cells compared to control wild-type cells. 相似文献
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Joha W. Grobbelaar Z. Wilhelm de Beer Paulette Bloomer Michael J. Wingfield Xu Dong Zhou Brenda D. Wingfield 《Mycoscience》2011,52(2):111-118
Ophiostoma species such as O. quercus are the most frequent causal agents of sapstain of freshly felled hardwood timber and pulpwood. Many species are regarded
as economically important agents of wood degradation. The aim of this study was to identify a collection of Ophiostoma isolates, resembling O. quercus, found on stained Eucalyptus pulpwood chips in China. DNA sequences of the internal transcribed spacer regions, including the 5.8S region, of the ribosomal
DNA, and parts of the β-tubulin and elongation factor-1α genes, revealed that the isolates were not O. quercus. Surprisingly, they represented O. tsotsi, a wound-infesting fungus recently described from hardwoods in Africa. In addition, sequence data from an isolate from agarwood
in Vietnam, identified in a previous study as belonging to an unknown Pesotum species, were also shown to represent O. tsotsi. A high level of genetic variability was observed among isolates of both O. quercus and O. tsotsi. This was unexpected and suggests that both species have been present in Asia for a significant amount of time. 相似文献
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Hiroyoshi Kubo 《Mycoscience》2009,50(5):400-406
Pilobolus crystallinus shows unique photoresponses at various growing stages. cDNAs for putative photoreceptors were cloned from this fungus. Three
genes named pcmada1, pcmada2, and pcmada3 were identified from the PCR fragments, and amplified with degenerated primers for the LOV domain, which is conserved in
many blue-light receptors. Deduced amino acid sequences for PCMADA1, PCMADA2, and PCMADA3 had one light-oxygen-voltage (LOV)-sensing
and two PER-ARNT-SIM (PAS) domains. A zinc finger DNA-binding motif was conserved in the C-terminals of PCMADA1 and PCMADA3.
However, PCMADA2 lacked the zinc finger motif. Expression of pcmada1 was suppressed by blue light whereas that of pcmada3 was promoted by blue-light irradiation. 相似文献
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O. V. Preobrajenskaya E. S. Starodubova V. L. Karpov J. Rouviere-Yaniv 《Molecular Biology》2005,39(4):585-592
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S. V. Malyshev T. V. Dolmatovich A. V. Voylokov S. P. Sosnikhina N. V. Tsvetkova A. V. Lovtsus N. A. Kartel’ 《Russian Journal of Genetics》2009,45(12):1444-1449
Studies of phenotypical expression of synaptic mutations in combination with the localization of corresponding genes on a
genetic map permit individual stages of the meiotic process to be differentiated. Two rye asynaptic genes, sy1 and sy9, were mapped with the use of microsatellite markers (SSR) in the pericentromeric regions of the long chromosome arms 7R and
2R, respectively. The sy9 gene cosegregated with two SSR markers Xscm43 and Xgwm132. The asynaptic gene sy1 was mapped within the interval between the isozyme locus Aat2 and two cosegregating loci Xrems1188 and Xrems1135 that are located at a distance of 0.4 cM proximally and 0.1 cM distally with respect to the gene lous. Possible evolutionary
relationships of the mapped genes with homeological loci of the Triticeae species and more distant cereal species, such as maize and rice, are discussed. 相似文献
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