Eukaryotic cells have evolved DNA damage response mechanisms utilizing proficient DNA repair and cell cycle checkpoints in order to maintain genomic stability. The Schizosaccharomyces pombe Rad9 gene was initially identified as encoding a cell cycle checkpoint protein. When the mammalian homologue of S. pombe Rad9 was inactivated, however, chromosomal instability was observed even in the absenc...

DNA double-strand breaks (DSBs) are biologically one of the most important cellular lesions and possess varying degrees of chemical complexity. The notion that the repairability of more chemically complex DSBs is inefficient led to the concept that the extent of DSB complexity underlies the severity of the biological consequences. The repair of DSBs by non-homologous end joining (NHEJ) has been...

BACKGROUND Depressive disorder (DD), including recurrent DD (rDD), is a severe psychological disease, which affects a large percentage of the world population. Although pathogenesis of the disease is not known, a growing body of evidence shows that inflammation together with oxidative stress may contribute to development of DD. Since reactive oxygen species produced during stress may damage DNA...

Molecular and cellular responses to protracted ionizing radiation exposures are poorly understood. Using immunofluorescence microscopy, we studied the kinetics of DNA repair foci formation in normal human fibroblasts exposed to X-rays at a dose rate of 4.5 mGy/min for up to 6 h. We showed that both the number of γH2AX foci and their integral fluorescence intensity grew linearly with time of irr...

We recently demonstrated that human embryonic stem cells (hESCs) utilize homologous recombination repair (HRR) as primary means of double-strand break (DSB) repair. We now show that hESCs also use nonhomologous end joining (NHEJ). NHEJ kinetics were several-fold slower in hESCs and neural progenitors (NPs) than in astrocytes derived from hESCs. ATM and DNA-PKcs inhibitors were ineffective or pa...

DNA damage (caused by direct cellular exposure and bystander signaling) and the complex pathways involved in its repair are critical events underpinning cellular and tissue response following radiation exposures. There are limited data addressing the dynamics of DNA damage induction and repair in the skin particularly in areas not directly exposed. Here we investigate the mechanisms regulating ...

The eukaryotic sliding DNA clamp, proliferating cell nuclear antigen (PCNA), is essential for DNA replication and repair synthesis. In order to load the ring-shaped, homotrimeric PCNA onto the DNA double helix, the ATPase activity of the replication factor C (RFC) clamp loader complex is required. Although the recruitment of PCNA by RFC to DNA replication sites has well been documented, our und...

Rates of DNA repair in ultraviolet (254 nm)-irradiated nondividing human diploid fibroblasts were determined at doses as low as 1 J/sq m using an enzymatic assay for pyrimidine dimers. In normal cells, initial rates (dimers removed per 24 hr) increased with dose to 20 J/sq m with no further increase at 40 J/sq m. At 10 J/sq m or less, repair occurred continuously over long postultraviolet perio...

The eukaryotic sliding DNA clamp, proliferating cell nuclear antigen (PCNA), is essential for DNA replication and repair synthesis. In order to load the ring-shaped, homotrimeric PCNA onto the DNA double helix, the ATPase activity of the replication factor C (RFC) clamp loader complex is required. Although the recruitment of PCNA by RFC to DNA replication sites has well been documented, our und...