Nuclear DNA

About: Nuclear DNA is a research topic. Over the lifetime, 3933 publications have been published within this topic receiving 185830 citations.

A head-to-tail tandem organization of hsp70 genes in Trypanosoma cruzi

Abstract: We describe the isolation and characterization of the T. cruzi hsp 70 DNA coding region which was found to be formed by multigene copies organized in a tandem array in a head-to-tail manner. The restriction pattern of one of the repetition units within the largest clone obtained from the genomic library, clone Tc70.6, shows that the hsp70 coding region should be formed by at least seven identical copies of 2.5 kb. We have found, however, the presence of restriction polymorphisms (Pvu II) within these repeats. Subsequent analysis of the time course of nuclear DNA digestion has revealed that the copy number per haploid genome could be as greater as 10. The analysis of the DNA and amino acid sequence of a fragment (70%) of one of the repetition units has shown the existence of a high homology with all the hsp70 genes of other organisms. The protein sequence homology of the fragment analyzed is as high as 88% when compared with that of the T. brucei hsp70. On the other hand, there are significant restriction site variations between both. The T. cruzi hsp70 contains at the C-terminal end a tetrapeptide repeat of the structure (GMPG)9.

Base J originally found in kinetoplastida is also a minor constituent of nuclear DNA of Euglena gracilis.

Abstract: We have analyzed DNA of Euglena gracilis for the presence of the unusual minor base β-D-glucosylhydroxymethyluracil or J, thus far only found in kinetoplastid flagellates and in Diplonema .U sing antibodies specific for J and post-labeling of DNA digests followed by two-dimensional thin-layer chromatography of labeled nucleotides, we show that ~0.2 mole percent of Euglena DNA consists of J, an amount similar to that found in DNA of Trypanosoma brucei. By staining permeabilized Euglena cells with anti-J antibodies, we show that J is rather uniformly distributed in the Euglena nucleus, and does not co-localize to a substantial extent with (GGGTTA) n repeats, the putative telomeric repeats of Euglena. Hence, most of J in Euglena appears to be non-telomeric. Our results add to the existing evidence for a close phylogenetic relation between kinetoplastids and euglenids.

High-resolution flow cytometry of nuclear DNA in higher plants

Abstract: High-resolution flow cytometry of nuclear DNA in higher plants has been performed from chopped plant tissues and plant protoplasts. A preparation and staining procedure with the DNA specific fluorochrome DAPI, successfully employed for precise flow cytometric DNA analysis of animal and human cells has been used in a slightly modified manner for the DNA analysis of plant cell material. High-resolution DNA histograms coefficients of variation about 1–1.5% have been obtained routinely from plant species with different DNA content. Staining of nuclei with DAPI in combination with the protein fluorochrome sulforhodamine 101 allows bi-parametric analysis of nuclear DNA and protein. The described simple and precise method might be very promising for the analysis of DNA in basic and applied cytogenetic investigations of plant cell research.

Interaction of benzo(a)pyrene and its dihydrodiol-epoxide derivative with nuclear and mitochondrial DNA in C3H10T 1/2 cell cultures.

Abstract: To analyze the distribution of radioactive carcinogens and [3H]thymidine between nuclear DNA (nDNA) and mitochondrial DNA (mtDNA), we have developed a simple and rapid method for the separation of nDNA and mtDNA using gel electrophoresis of cell lysates. Using this method, we found that, when C3H10T 1/2 cells are exposed to either 0.5 microM [3H]-(+/-)-7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenzo(a)pyrene ([3H]BPDE) or 1 microM [3H]benzo(a)pyrene, the mtDNA contains a major fraction of the total adducts formed with cellular DNAs. Deoxynucleoside adducts formed between benzo(a)pyrene and mtDNA in intact C3H10T 1/2 cells or between BPDE and isolated rat liver mtDNA were analyzed by high-performance liquid chromatography, and were found to be much more heterogeneous than those present in nDNA of C3H10T 1/2 cells. The extensive modification of mtDNA in BPDE in C3H10T 1/2 cells is associated with preferential inhibition of the incorporation of [3H]thymidine into mtDNA, when compared to incorporation of [3H]thymidine into nDNA. To analyze the factors responsible for the extensive modification of mtDNA by BPDE, we investigated the role of a lipid phase utilizing liposome:DNA complexes as a model system. We found that the liposomes protect BPDE from spontaneous hydrolysis and enhance the extent of DNA modification at low DNA concentrations. These findings extent previous evidence suggesting that the mitochondria may be important cellular targets in the process of chemical carcinogenesis.

The oxidative damage initiation hypothesis for meiosis.

Abstract: The maintenance of sexual reproduction in eukaryotes is still a major enigma in evolutionary biology. Meiosis represents the only common feature of sex in all eukaryotic kingdoms, and thus, we regard it a key issue for discussing its function. Almost all asexuality modes maintain meiosis either in a modified form or as an alternative pathway, and facultatively apomictic plants increase frequencies of sexuality relative to apomixis after abiotic stress. On the physiological level, abiotic stress causes oxidative stress. We hypothesize that repair of oxidative damage on nuclear DNA could be a major driving force in the evolution of meiosis. We present a hypothetical model for the possible redox chemistry that underlies the binding of the meiosis-specific protein Spo11 to DNA. During prophase of meiosis I, oxidized sites at the DNA molecule are being targeted by the catalytic tyrosine moieties of Spo11 protein, which acts like an antioxidant reducing the oxidized target. The oxidized tyrosine residues, tyrosyl radicals, attack the phosphodiester bonds of the DNA backbone causing DNA double strand breaks that can be repaired by various mechanisms. Polyploidy in apomictic plants could mitigate oxidative DNA damage and decrease Spo11 activation. Our hypothesis may contribute to explaining various enigmatic phenomena: first, DSB formation outnumbers crossovers and, thus, effective recombination events by far because the target of meiosis may be the removal of oxidative lesions; second, it offers an argument for why expression of sexuality is responsive to stress in many eukaryotes; and third, repair of oxidative DNA damage turns meiosis into an essential characteristic of eukaryotic reproduction.