Search results for "Chromosomes"
showing 10 items of 509 documents
Excision of Uracil from Transcribed DNA Negatively Affects Gene Expression
2014
Uracil is an unavoidable aberrant base in DNA, the repair of which takes place by a highly efficient base excision repair mechanism. The removal of uracil from the genome requires a succession of intermediate products, including an abasic site and a single strand break, before the original DNA structure can be reconstituted. These repair intermediates are harmful for DNA replication and also interfere with transcription under cell-free conditions. However, their relevance for cellular transcription has not been proved. Here we investigated the influence of uracil incorporated into a reporter vector on gene expression in human cells. The expression constructs contained a single uracil opposi…
The high rate of endoreduplication in the repair deficient CHO mutant EM9 parallels a reduced level of methylated deoxycytidine in DNA
2008
It has been recently proposed that hypomethylation of DNA induced by 5-azacytidine (5-azaC) leads to reduced chromatid decatenation that ends up in endoreduplication, most likely due to a failure in topo II function [S. Mateos, I. Domínguez, N. Pastor, G. Cantero, F. Cortés, The DNA demethylating 5-azaC induces endoreduplication in cultured Chinese hamster cells, Mutat. Res. 578 (2005) 33-42]. The Chinese hamster mutant cell line EM9 has a high spontaneous frequency of endoreduplication as compared to its parental line AA8. In order to see if this is related to the degree of DNA methylation, we have investigated the basal levels of both endpoints in AA8 and EM9, as well as the effect of ext…
Asynchronous replication dynamics of imprinted and non-imprinted chromosome regions in early mouse embryos.
2008
We have used interphase FISH to analyze the replication behavior of four imprinted chromosome regions (Snrpn, Zim1-Peg3, Dlk1-Gtl2, and Igf2r) and five non-imprinted regions in mouse one-cell to morula-stage embryos and embryonic fibroblasts. In general, imprinted chromosome regions showed the expected asynchronous pattern of replication throughout all analyzed stages of preimplantation development and in differentiated cells. The Dlk1-Gtl2 locus which is not expressed and Igf2r which is biallelically expressed in early embryos showed a relaxation of replication asynchrony at the morula stage. Asynchronous replication in zygotes and two-cell embryos was not specific to imprinted regions. Th…
Chromosomal instability, reproductive cell death and apoptosis induced by O6-methylguanine in Mex−, Mex+ and methylation-tolerant mismatch repair com…
1998
O6-Methylguanine (O6-MeG) is induced in DNA by methylating environmental carcinogens and various cytostatic drugs. It is repaired by O6-methylguanine-DNA methyltransferase (MGMT). If not repaired prior to replication, the lesion generates gene mutations and leads to cell death, sister chromatid exchanges (SCEs), chromosomal aberrations and malignant transformation. To address the question of how O6-MeG is transformed into genotoxic effects, isogenic Chinese hamster cell lines either not expressing MGMT (phenotypically Mex-), expressing MGMT (Mex+) or exhibiting the tolerance phenotype (Mex-, methylation resistant) were compared as to their clastogenic response. Mex- cells were more sensitiv…
Multiple roles for ISWI in transcription, chromosome organization and DNA replication.
2003
ISWI functions as the ATPase subunit of multiple chromatin-remodeling complexes. These complexes use the energy of ATP hydrolysis to slide nucleosomes and increase chromatin fluidity, thereby modulating the access of transcription factors and other regulatory proteins to DNA. Here we discuss recent progress toward understanding the biological functions of ISWI, with an emphasis on its roles in transcription, chromosome organization and DNA replication.
Expression in Streptomyces lividans of Nonomuraea genes cloned in an artificial chromosome
2004
A bacterial artificial chromosomal library of Nonomuraea sp. ATCC39727 was constructed using Escherichia coli-Streptomyces artificial chromosome (ESAC) and screened for the presence of dbv genes known to be involved in the biosynthesis of the glycopeptide A40926. dbv genes were cloned as two large, partially overlapping, fragments and transferred into the host Streptomyces lividans, thus generating strains S. lividansColon, two colonsNmESAC50 and S. lividansColon, two colonsNmESAC57. The heterologous expression of Nonomuraea genes in S. lividans was successfully demonstrated by using combined RT-PCR and proteomic approaches. MALDI-TOF analysis revealed that a Nonomuraea ABC transporter is e…
Transformation of follicular lymphoma to diffuse large cell lymphoma is associated with a heterogeneous set of DNA copy number and gene expression al…
2002
AbstractGenomic aberrations in a series of paired biopsy samples from patients who presented initially with follicle center lymphoma (FCL) and subsequently transformed to diffuse large B-cell lymphoma (DLBCL) were measured by array comparative genomic hybridization (CGH). The consequences of these aberrations on gene expression were determined by comparison with expression analysis on these specimens using cDNA microarrays. A heterogeneous pattern of acquired genomic abnormalities was observed upon transformation, some of which were recurrent in small subsets of patients. Some of the genomic aberration acquired upon transformation, such as gain/amplification of 1q21-q24, 2p16 (REL/BCL11A ge…
Identification of a novel Drosophila melanogaster gene, angel, a member of a nested gene cluster at locus 59F4,5.
1996
The identification of a novel Drosophila melanogaster gene, angel, is presented in this study. angel is located on the right arm of the second chromosome at locus 59F5, close to the nested genes l(2)tid, l(2)not, l(2)rot and l(2)dtl. We describe the genetic and molecular localization of angel and present its temporal expression in the wild-type. The deduced amino acid sequence of the ANG39 protein is characterized by a nuclear localization signal. Furthermore, the central part of the predicted ANG39 protein shows significant homology to the C-terminal portion of the yeast transcriptional effector CCR4.
Expression profiling of uniparental mouse embryos is inefficient in identifying novel imprinted genes
2006
AbstractImprinted genes are expressed from only one allele in a parent-of-origin-specific manner. We here describe a systematic approach to identify novel imprinted genes using quantification of allele-specific expression by Pyrosequencing, a highly accurate method to detect allele-specific expression differences. Sixty-eight candidate imprinted transcripts mapping to known imprinted chromosomal regions were selected from a recent expression profiling study of uniparental mouse embryos and analyzed. Three novel imprinted transcripts encoding putative non-protein-coding RNAs were identified on the basis of parent-of-origin-specific monoallelic expression in E11.5 (C57BL/6 × Cast/Ei)F1 and in…
Impact of polyploidy on fertility variation of Mediterranean Arundo L. (Poaceae)
2015
International audience; Failure of seed production in the genus Arundo L. (Poaceae) is often attributed to polyploidy. This study tested the impact of two ploidy levels (2n = 12 and 18x) on the fertility of four Mediterranean Arundo. Viable pollen was screened from its production to its germination, and seed occurrence was monitored in admixture or isolated conditions. In addition, insights on restructuration of polyploid genornes were analysed using molecular cytogenetics. Our results show that high ploidy levels do not automatically induce failure of sexual reproduction. The two ploidy levels are able to produce viable pollen and seed set depending on species and cultural conditions. The …