Biomaterial Database

Repair of DNA single-strand breaks in X-irradiated yeast. II. Kinetics of repair as measured by the DNA-unwinding method. 1985

B Ogorek, and P E Bryant

The kinetics of disappearance of single-strand breaks (SSB) from the DNA of X-irradiated stationary yeast cells under liquid-holding conditions was found to proceed in a dose-independent manner up to a dose of at least 2400 Gy, and was found to be complete after incubation of cells for 1 h. This was deduced from data for a yeast wild-type (WT) haploid and diploid strain as well as for rad52 haploid cells defective in DNA double-strand break (DSB) repair. In all cases an initial fast repair component assumed to correspond to SSB repair was observed whereby about 80% of the induced 'unwinding points' disappeared from the DNA with a time constant of about 3 min. Following this fast component, a slower component of removal of 'unwinding points' occurred with a time constant estimated to be 20 min. The molecular nature of these two components of repair is not known. We could find no evidence for the induction of secondary (enzymatic) breaks in the DNA during post-irradiation incubation. Incubation of cells in growth medium after irradiation resulted in similar kinetics as those under liquid-holding conditions. In the absence of an energy source in the medium (i.e. when cells were incubated in buffer or distilled water after irradiation) only 60-80% of the SSB were removed from yeast DNA. Residual SSB disappeared from the DNA only when cells were transferred to a medium containing glucose. The relative mass of DNA unwound per induced strand break (i.e. represented by the slope of the dose-effect curve immediately after irradiation) was found to change slowly with the age of the cell culture under liquid-holding conditions. This effect had to be corrected for in the measurements of strand break repair under these conditions.

UI	MeSH Term	Description	Entries
D007700	Kinetics	The rate dynamics in chemical or physical systems.
D008722	Methods	A series of steps taken in order to conduct research.	Techniques,Methodological Studies,Methodological Study,Procedures,Studies, Methodological,Study, Methodological,Method,Procedure,Technique
D009691	Nucleic Acid Denaturation	Disruption of the secondary structure of nucleic acids by heat, extreme pH or chemical treatment. Double strand DNA is "melted" by dissociation of the non-covalent hydrogen bonds and hydrophobic interactions. Denatured DNA appears to be a single-stranded flexible structure. The effects of denaturation on RNA are similar though less pronounced and largely reversible.	DNA Denaturation,DNA Melting,RNA Denaturation,Acid Denaturation, Nucleic,Denaturation, DNA,Denaturation, Nucleic Acid,Denaturation, RNA,Nucleic Acid Denaturations
D003470	Culture Media	Any liquid or solid preparation made specifically for the growth, storage, or transport of microorganisms or other types of cells. The variety of media that exist allow for the culturing of specific microorganisms and cell types, such as differential media, selective media, test media, and defined media. Solid media consist of liquid media that have been solidified with an agent such as AGAR or GELATIN.	Media, Culture
D004260	DNA Repair	The removal of DNA LESIONS and/or restoration of intact DNA strands without BASE PAIR MISMATCHES, intrastrand or interstrand crosslinks, or discontinuities in the DNA sugar-phosphate backbones.	DNA Damage Response
D004271	DNA, Fungal	Deoxyribonucleic acid that makes up the genetic material of fungi.	Fungal DNA
D004277	DNA, Single-Stranded	A single chain of deoxyribonucleotides that occurs in some bacteria and viruses. It usually exists as a covalently closed circle.	Single-Stranded DNA,DNA, Single Stranded,Single Stranded DNA
D012441	Saccharomyces cerevisiae	A species of the genus SACCHAROMYCES, family Saccharomycetaceae, order Saccharomycetales, known as "baker's" or "brewer's" yeast. The dried form is used as a dietary supplement.	Baker's Yeast,Brewer's Yeast,Candida robusta,S. cerevisiae,Saccharomyces capensis,Saccharomyces italicus,Saccharomyces oviformis,Saccharomyces uvarum var. melibiosus,Yeast, Baker's,Yeast, Brewer's,Baker Yeast,S cerevisiae,Baker's Yeasts,Yeast, Baker
D013696	Temperature	The property of objects that determines the direction of heat flow when they are placed in direct thermal contact. The temperature is the energy of microscopic motions (vibrational and translational) of the particles of atoms.	Temperatures