UV-induced histone H2AX phosphorylation and DNA damage related proteins accumulate and persist in nucleotide excision repair-deficient XP-B cells (original) (raw)

Molecular mechanisms of ultraviolet radiation-induced DNA damage and repair

Journal of nucleic acids, 2010

DNA is one of the prime molecules, and its stability is of utmost importance for proper functioning and existence of all living systems. Genotoxic chemicals and radiations exert adverse effects on genome stability. Ultraviolet radiation (UVR) (mainly UV-B: 280-315 nm) is one of the powerful agents that can alter the normal state of life by inducing a variety of mutagenic and cytotoxic DNA lesions such as cyclobutane-pyrimidine dimers (CPDs), 6-4 photoproducts (6-4PPs), and their Dewar valence isomers as well as DNA strand breaks by interfering the genome integrity. To counteract these lesions, organisms have developed a number of highly conserved repair mechanisms such as photoreactivation, base excision repair (BER), nucleotide excision repair (NER), and mismatch repair (MMR). Additionally, double-strand break repair (by homologous recombination and nonhomologous end joining), SOS response, cell-cycle checkpoints, and programmed cell death (apoptosis) are also operative in various ...

UV-induced DNA damage and repair: a review

Photochemical & Photobiological Sciences, 2002

Increases in ultraviolet radiation at the Earth's surface due to the depletion of the stratospheric ozone layer have recently fuelled interest in the mechanisms of various effects it might have on organisms. DNA is certainly one of the key targets for UV-induced damage in a variety of organisms ranging from bacteria to humans. UV radiation induces two of the most abundant mutagenic and cytotoxic DNA lesions such as cyclobutane-pyrimidine dimers (CPDs) and 6-4 photoproducts (6-4PPs) and their Dewar valence isomers. However, cells have developed a number of repair or tolerance mechanisms to counteract the DNA damage caused by UV or any other stressors. Photoreactivation with the help of the enzyme photolyase is one of the most important and frequently occurring repair mechanisms in a variety of organisms. Excision repair, which can be distinguished into base excision repair (BER) and nucleotide excision repair (NER), also plays an important role in DNA repair in several organisms with the help of a number of glycosylases and polymerases, respectively. In addition, mechanisms such as mutagenic repair or dimer bypass, recombinational repair, cell-cycle checkpoints, apoptosis and certain alternative repair pathways are also operative in various organisms. This review deals with UV-induced DNA damage and the associated repair mechanisms as well as methods of detecting DNA damage and its future perspectives.

The relative roles of DNA damage induced by UVA irradiation in human cells

Photochemical & Photobiological Sciences, 2013

UVA light (320-400 nm) represents approximately 95% of the total solar UV radiation that reaches the Earth's surface. UVA light induces oxidative stress and the formation of DNA photoproducts in skin cells. These photoproducts such as pyrimidine dimers (cyclobutane pyrimidine dimers, CPDs, and pyrimidine (6-4) pyrimidone photoproducts, 6-4PPs) are removed by nucleotide excision repair (NER). In this repair pathway, the XPA protein is recruited to the damage removal site; therefore, cells deficient in this protein are unable to repair the photoproducts. The aim of this study was to investigate the involvement of oxidative stress and the formation of DNA photoproducts in UVA-induced cell death. In fact, similar levels of oxidative stress and oxidised bases were detected in XP-A and NER-proficient cells exposed to UVA light. Interestingly, CPDs were detected in both cell lines; however, 6-4PPs were detected only in DNA repairdeficient cells. XP-A cells were also observed to be significantly more sensitive to UVA light compared to NER-proficient cells, with an increased induction of apoptosis, while necrosis was similarly observed in both cell lines. The induction of apoptosis and necrosis in XP-A cells using adenovirus-mediated transduction of specific photolyases was investigated and we confirm that both types of photoproducts are the primary lesions responsible for inducing cell death in XP-A cells and may trigger the skin-damaging effects of UVA light, particularly skin ageing and carcinogenesis. † Electronic supplementary information (ESI) available. See

Evidence for a novel DNA damage binding protein in human cells

Proceedings of the National Academy of Sciences, 1996

We describe a novel DNA damage binding activity in nuclear extracts from a normal human fibroblast cell strain. This protein was identified using electrophoretic mobility shift assays of immunopurified UV-irradiated oligonucleotide substrates containing a single, site-specific cyclobutane pyrimidine dimer or a pyrimidine (6-4) pyrimidinone photoproduct. Compared with the (6-4) photoproduct, which displayed similar levels of binding in double and single-stranded substrates, the protein showed somewhat lower affinity for the cyclobutane dimer in a single-stranded oligonucleotide and negligible binding in double-stranded DNA. The specificity and magnitude of binding was similar in cells with normal excision repair (GM637) and repairdeficient cells from xeroderma pigmentosum groups A (XP12RO) and E (XP2RO). An apparent molecular mass of 66 kDa consisting of two subunits of-22 and-44 kDa was determined by Southwestern analysis. Cell cycle studies using centrifugal cell elutriation indicated that the binding activity was significantly greater in Gl phase compared with S phase in a human lymphoblast cell line. Gel supershift analysis using an anti-replication protein A antibody showed that the binding protein was not antigenically related to the human single-stranded binding protein. Taken together, these data suggest that this activity represents a novel DNA damage binding protein that, in addition to a putative role in excision repair, may also function in cell cycle or gene regulation. Nucleotide excision repair (NER) is the principal defense mechanism used by cells to mitigate the lethal, mutagenic, and carcinogenic effects of DNA damage caused by exposure to genotoxic agents, such as solar UV radiation. Many of the proteins involved in the NER pathway have been identified by complementation of the repair-deficient autosomal recessive

Sequential binding of UV DNA damage binding factor and degradation of the p48 subunit as early events after UV irradiation

Nucleic Acids Research, 2002

The UV-damaged DNA binding protein complex (UV-DDB) is implicated in global genomic nucleotide excision repair (NER) in mammalian cells. The complex consists of a heterodimer of p127 and p48. UV-DDB is defective in one complementation group (XP-E) of the heritable, skin cancer-prone disorder xeroderma pigmentosum. Upon UV irradiation of primate cells, UV-DDB associates tightly with chromatin, concomitant with the loss of extractable binding activity. We report here that an early event after UV, but not ionizing, radiation is the transient dose-dependent degradation of the small subunit, p48. Treatment of human cells with the proteasomal inhibitor NIP-L 3 VS blocks this UV-induced degradation of p48. In XP-E cell lines with impaired UV-DDB binding, p48 is resistant to degradation. UV-mediated degradation of p48 occurs independently of the expression of p53 and the cell's proficiency for NER, but recovery of p48 levels at later times (12 h and thereafter) is dependent upon the capacity of the cell to repair non-transcribed DNA. In addition, we find that the p127 subunit of UV-DDB binds in vivo to p300, a histone acetyltransferase. The data support a functional connection between UV-DDB binding activity, proteasomal degradation of p48 and chromatin remodeling during early steps of NER.

UV Irradiation Triggers Ubiquitin-Dependent Degradation of p21< sup> WAF1 to Promote DNA Repair

2003

1995). Besides DNA replication, nucleotide excision repair (NER), the major pathway by which damage is re-1 Institut de Biologie Structurale J.-P. Ebel 41 rue Jules Horowitz moved after UV irradiation, also requires PCNA. This repair process involves recognition of the damage fol-F38027 Grenoble France lowed by a dual incision that cuts the damaged DNA strand on either side of the lesion and release of the 2 Sidney Kimmel Cancer Center 10835 Altman Road oligonucleotide fragment containing the damaged site (reviewed in Wood, 1996). The resulting gap of about San Diego, California 92121 3 Institut Gustave Roussy 30 nucleotides is filled by DNA polymerases ⑀ and ␦ together with accessory proteins including PCNA (Nich-rue Camille Desmoulins 94805 Villejuif ols and Sancar, 1992; Shivji et al., 1992). p21 has been shown to reduce repair in vivo (Cooper et al., 1999) or France to have modest effect (Adimoolam et al., 2001; Smith et al., 2000). In vitro DNA repair assays similarly show either inhibition of DNA repair (Pan et al., 1995; Shivji et al., Summary 1998) or no effect of p21 on DNA repair (Li et al., 1994; Shivji et al., 1994). Evidently, the effect of p21 on DNA p53-mediated increase in cyclin-dependent kinase inhibitor p21 WAF1 protein is thought to be the major medi-repair remains unresolved. Proteasome inhibition results in accumulation of p21 ator of cell cycle arrest after DNA damage. Previously p21 protein levels have been reported to increase or protein and in an increase in the half-life of p21 (Blagosklonny et al., 1996; Cayrol et al., 1998; Maki and to decrease after UV irradiation. We show that p21 protein is degraded after irradiation of a variety of cell Howley, 1997; Rousseau et al., 1999; Sheaff et al., 2000). Interestingly, we now find that low but not high doses types with low but not high doses of UV. Cell cycle arrest occurs despite p21 degradation via Tyr 15 inhibi-of UV irradiation lead to rapid loss of p21 protein due to a decrease in half-life of p21. In this study, we have tory phosphorylation of cdk2 and differs from the classical p21-dependent checkpoint elicited by ionizing focused on the regulation of p21 degradation induced by low doses of UV and its functional consequences on radiation. In contrast to the basal turnover of p21, degradation of p21 switches to ubiquitin/Skp2-depen-the checkpoint response. dent proteasome pathway following UV irradiation. ATR activation after UV irradiation is essential for sig-Results naling p21 degradation. Finally, UV-induced p21 degradation is essential for optimal DNA repair. These Degradation of Endogenous p21 Protein results provide novel insight into regulation of p21 at Low UV Doses protein and its role in the cellular response to DNA During the course of our studies on DNA damage indamage. duced changes in p21, we surprisingly found that low but not high doses of UV irradiation led to a sharp decline

Double-strand breaks in DNA caused by repair of damage due to ultraviolet light

Journal of Supramolecular Structure and Cellular Biochemistry, 1981

DNA DSBs are formed in normal human IMR-90 cells during repair incubation after 100 and 300 J*m-2 of UVL. By contrast, no DSBs are formed after UVL in human XPA cells that are unable to excise pyrimidine dimers. The DSBs are not due to immediate cell death since all the cells excluded trypan blue at the time of assay and because XPA cells, which are much more UVLsensitive than IMR-90, did not form DSBs after UVL. We suggest that these repair-induced DSBs should be potent lesions that might lead to cytotoxicity, chromosome aberrations, deletion mutations, and perhaps cellular transformation. transformation.