The yields of unrepairable single-and double-strand breaks in the DNA of x-irradiated Chinese hamster cells were measured by low-speed neutral and alkaline sucrose density gradient sedimentation in order to investigate the relation between these lesions and reproductive death. After maximal single-strand remoining, at all doses, the number of residual single-strand breaks was twice the number o...

In spite of its essential role as the carrier of genetic information, DNA is not an inert structure. The genome is susceptible to potentially mutagenic threats of both endogenous and environmental origin. A dramatic threat to the covalent structure of DNA is posed by breaks in the phosphate backbone affecting one or both strands of the Watson–Crick double helix. Ionizing radiation and certain c...

DNA single-strand break repair (SSBR) is critical for the survival and genetic stability of mammalian cells. Three papers have recently associated mutations in putative human SSBR genes with hereditary spinocerebellar ataxia. The emerging links between SSBR and neurodegenerative disorders are discussed.

Objective: Coronary heart disease (CHD) is one of the most common diseases. Coronary angiography (CAG) is an important apparatus used to diagnose and treat this disease. Since angiography is performed through exposure to ionizing radiation, it can cause harmful effects induced by double-stranded breaks in DNA which is potentially life-threatening damage. The aim of the present study is to inves...

The repair of chromosomal double-strand breaks (DSBs) is essential to normal cell growth, and homologous recombination is a universal process for DSB repair. We explored DSB repair mechanisms in the yeast Saccharomyces cerevisiae using single-strand oligonucleotides with homology to both sides of a DSB. Oligonucleotide-directed repair occurred exclusively via Rad52- and Rad59-mediated single-st...

DNA single-strand breaks (SSBs) are the commonest DNA lesions that arise spontaneously in living cells. Cells employ efficient processes for the rapid repair of these breaks and defects in these processes appear to preferentially impact on the nervous system, causing human ataxia. Spinocerebellar ataxia with axonal neuropathy (SCAN1) is a human disease that is associated with a defect in repair...

The study of double-strand break repair and homologous recombination in Saccharomyces cerevisiae meiosis has provided important information about the mechanisms involved. However, it has become clear that the resulting recombination models are only partially applicable to repair in mitotic cells, where crossover formation is suppressed. In recent years our understanding of double-strand break r...

Mating-type switching in the fission yeast Schizosaccharomyces pombe is initiated by a strand-specific imprint located at the mating-type (mat1) locus. We show that the imprint corresponds to a single-strand DNA break (SSB), which is site- but not sequence-specific. We identified three novel cis-acting elements, involved in the formation and stability of the SSB. One of these elements is essent...

During meiosis, self-inflicted DNA double-strand breaks (DSBs) are created by the protein Spo11 and repaired by homologous recombination leading to gene conversions and crossovers. Crossover formation is vital for the segregation of homologous chromosomes during the first meiotic division and requires the RecA orthologue, Dmc1. We analyzed repair during meiosis of site-specific DSBs created by ...

Wortmannin, an inhibitor of p110 PI 3-kinase, also inhibits DNA-dependent protein kinase, which is known to mediate DNA double strand break repair. It was recently demonstrated that wortmannin sensitized cells to ionizing radiation (IR) (Price and Youmell, Cancer Res., 56, 246-250, 1996). Wortmannin was used to determine if the potentiation of IR-induced cytotoxicity in Chinese hamster ovary ce...