40 research outputs found
The human DNA glycosylases NEIL1 and NEIL3 excise psoralen-induced DNA-DNA cross-links in a four-stranded DNA structure
Interstrand cross-links (ICLs) are highly cytotoxic DNA lesions that block DNA replication and transcription by preventing strand separation. Previously, we demonstrated that the bacterial and
human DNA glycosylases Nei and NEIL1 excise unhooked psoralen-derived ICLs in three-stranded DNA via hydrolysis of the glycosidic bond between the crosslinked base and deoxyribose sugar. Furthermore, NEIL3 from Xenopus laevis has been shown to cleave psoralen- and abasic site-induced ICLs in Xenopus
egg extracts. Here we report that human NEIL3 cleaves psoralen-induced DNA-DNA cross-links in three-stranded and four-stranded DNA substrates to generate unhooked DNA fragments containing
either an abasic site or a psoralen-thymine monoadduct. Furthermore, while Nei and NEIL1 also cleave a psoralen-induced four-stranded DNA substrate to generate two unhooked DNA duplexes with a nick, NEIL3 targets both DNA strands in the ICL without generating single-strand breaks. The DNA substrate specificities of these Nei-like enzymes imply the occurrence of long uninterrupted three- and four-stranded crosslinked DNA-DNA structures that may originate in vivo from DNA replication fork
bypass of an ICL. In conclusion, the Nei-like DNA glycosylases unhook psoralen-derived ICLs in various DNA structures via a genuine repair mechanism in which complex DNA lesions can be removed without generation of highly toxic double-strand breaks
Mismatch repair and nucleotide excision repair proteins cooperate in the recognition of DNA interstrand crosslinks
DNA interstrand crosslinks (ICLs) are among the most cytotoxic types of DNA damage, thus ICL-inducing agents such as psoralen, are clinically useful chemotherapeutics. Psoralen-modified triplex-forming oligonucleotides (TFOs) have been used to target ICLs to specific genomic sites to increase the selectivity of these agents. However, how TFO-directed psoralen ICLs (Tdp-ICLs) are recognized and processed in human cells is unclear. Previously, we reported that two essential nucleotide excision repair (NER) protein complexes, XPAāRPA and XPCāRAD23B, recognized ICLs in vitro, and that cells deficient in the DNA mismatch repair (MMR) complex MutSĪ² were sensitive to psoralen ICLs. To further investigate the role of MutSĪ² in ICL repair and the potential interaction between proteins from the MMR and NER pathways on these lesions, we performed electrophoretic mobility-shift assays and chromatin immunoprecipitation analysis of MutSĪ² and NER proteins with Tdp-ICLs. We found that MutSĪ² bound to Tdp-ICLs with high affinity and specificity in vitro and in vivo, and that MutSĪ² interacted with XPAāRPA or XPCāRAD23B in recognizing Tdp-ICLs. These data suggest that proteins from the MMR and NER pathways interact in the recognition of ICLs, and provide a mechanistic link by which proteins from multiple repair pathways contribute to ICL repair
Etude de la voie de signalisation Sonic hedgehog dans les cancers cutanƩs de patients atteints de Xeroderma pigmentosum
PARIS7-BibliothĆØque centrale (751132105) / SudocSudocFranceF
Epigenetic silencing contributes to frequent loss of the fragile histidine triad tumour suppressor in basal cell carcinomas
Zic2 synergistically enhances Hedgehog signalling through nuclear retention of Gli1 in cervical cancer cells
Human DNA polymerase iota protects cells against oxidative stress
Human DNA polymerase iota (polĪ¹) is a unique member of the Y-family of specialised polymerases that displays a 5ā²deoxyribose phosphate (dRP) lyase activity. Although polĪ¹ is well conserved in higher eukaryotes, its role in mammalian cells remains unclear. To investigate the biological importance of polĪ¹ in human cells, we generated fibroblasts stably downregulating polĪ¹ (MRC5-polĪ¹KD) and examined their response to several types of DNA-damaging agents. We show that cell lines downregulating polĪ¹ exhibit hypersensitivity to DNA damage induced by hydrogen peroxide (H2O2) or menadione but not to ethylmethane sulphonate (EMS), UVC or UVA. Interestingly, extracts from cells downregulating polĪ¹ show reduced base excision repair (BER) activity. In addition, polĪ¹ binds to chromatin after treatment of cells with H2O2 and interacts with the BER factor XRCC1. Finally, green fluorescent protein-tagged polĪ¹ accumulates at the sites of oxidative DNA damage in living cells. This recruitment is partially mediated by its dRP lyase domain and ubiquitin-binding domains. These data reveal a novel role of human polĪ¹ in protecting cells from oxidative damage