Nuclear DNA

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

Studies on basophilia of nucleic acids: the methyl green stainability of nucleic acids

Abstract: 1. The capacity of nucleic acids to combine with basic dyes under various conditions was investigated by means of fixed tissues and model systems. Observations and experiments suggest that the specificity for nuclear DNA which methyl green exhibits in many, but not all, tissues is caused by blockage of stainable groups of ribonucleic acid by protein.2. Nuclear staining with methyl green is also subject to modification by changes in the degree of protein interference, and impairment of stainability cannot be correlated unequivocally with depolymerization of DNA.3. Since variable degrees of RNA staining, differences in the extent to which DNA staining is affected by protein interference, and possibly changes in the degree of polymerization of the DNA may all influence the staining intensity of nuclei, methyl green staining is not a very suitable method for quantitative determination of DNA in cell nuclei.

Modification of the Radiation Sensitivity of Human Tumour Cells by a Bis-benzimidazole Derivative

Abstract: A comparison was made of the ability of either X-radiation or a DNA-specific ligand (the vital bis-benzimidazole dye; Hoechst 33342) to induce: cell killing, inhibition of de novo DNA synthesis, DNA strand breakage and the delay of cell division in human colon adenocarcinoma cells in vitro. Unlike radiation-induced cell killing, ligand-induced cytotoxicity appeared to be positively correlated with the extent of inhibition of de novo DNA synthesis--a feature consistent with the persistent binding of ligand molecules to nuclear DNA. Ligand-induced DNA strand-breaks disappeared slowly although ligand-treated cells retained apparently normal capacities to repair discrete radiogenic DNA strand-breaks. Pre-treatment of cells with Hoechst 33342 resulted in a dose-modifying enhancement of radiation resistance not associated with altered dosimetry for strand-break induction. However, radioresistance was accompanied by the protracted retention of cells in the G2 phase of the cell cycle. We suggest that the results provide direct evidence that the retention of cells in G2 phase is a sparing phenomenon and is triggered by the responses of chromatin domains to the presence of DNA damage. Our results have implications for the use of DNA-interactive agents in combined modalities for tumour therapy, and indicate a possible basis for the sparing of some tumour cells in dividing populations.

Escherichia coli plasmid pBR313 insertion into plant protoplasts and into their nuclei.

Abstract: Cowpea mesophyll protoplasts were shown to bind irreversibly up to 3% input radioactive pBR313 plasmid DNA after 15 min of contact. Maximum uptake occurred in the presence of 5mM ZnSO4 and 5 μg/ml poly-L-ornithine. Under these conditions about one half of the TCA precipitable radioactivity was associated with the nuclear fraction and behaved as linear plasmid molecules. These could not be chased from the protoplasts upon further incubation with unlabeled plasmid DNA. The presence of donor DNA within the nuclear fraction is most probably not due to an artifactual redistribution of adsorbed plasmid DNA. Prolonged incubation periods resulted in extensive degradation of plasmid in the incubation medium but little degradation occurred in the protoplasts. The donor DNA was not covalently associated with the protoplast nuclear DNA.

Mitochondrial DNA in aging and degenerative disease

Abstract: The mitochondrial DNA encodes only a few gene products compared to the nuclear DNA. These products, however, play a decisive role in determining cell function. Should this DNA mutate spontaneously or be damaged by free radicals the functionality of the gene products will be compromised. A number of mitochondrial genetic diseases have been identified. Some of these are quite serious and involve the central nervous system as well as muscle, heart, liver and kidney. Aging has been characterized by a gradual increase in base deletions in this DNA. This increase in deletion mutation has been suggested to be the cumulative result of exposure to free radicals.