DNA polymerase β (Polβ) inserts then one nucleotide and removes the dRP group. This site is then incised by apurinic/apyrimidinic endonuclease 1 (APE1), which leads to a nick with the 5ʹ-deoxyribose phosphate (dRP) and 3ʹ-hydroxyl group. In the so-called short-patch (SP) pathway, a specific DNA glycosylase removes a damaged nucleobase with the formation of an AP site. The generally accepted BER model in mammalian cells involves two pathways. The whole-cell extracts, which differ in the efficiency of PAR synthesis, seem to be an attractive model system for this purpose since the ratios of proteins in the extracts reflect their state in real cells.īER is one of the main strategies of cellular defense against single-base lesions in DNA. Taking into account the known roles of PARPs and their activity in the BER process, we were interested in studying the effect of PARylation on DNA repair synthesis on the specific substrates of BER. In addition, Hgl cell extracts contain higher amounts of PARP1 as revealed by cross-linking of the extract proteins to chemically reactive DNA intermediates bearing photoreactive nucleotide analogs or AP sites. The level of the poly(ADP-ribose) (PAR) synthesis catalyzed by poly(ADP-ribose) polymerases (PARPs) was also higher in Hgl cell extracts. Hgl cell extracts were slightly more efficient compared to Mmu in the removal of the uracil residues and cleavage of the abasic (AP) sites but not in the DNA synthesis on the BER substrates. Using extracts from Hgl and mouse (Mus musculus, Mmu) fibroblasts we compared the activities of some enzymes involved in base excision repair (BER). However until recently DNA repair efficiency in Hgl cells has not been directly tested. The naked mole rat ( Heterocephalus glaber, Hgl) is a long‐lived and tumor‐resistant rodent. Our results suggest that MARylation/PARylation of DNA in the extracts depends on the ratios between PARPs and can be controlled by DNA-binding proteins.ĭNA repair systems are considered as a key factor in mammalian cells, which counteracts genomic instability and is associated with aging and oncogenesis. PARP1/PARP2 can then transfer the ADP-ribose moieties onto initial ADP-ribose. The results obtained with WCEs, recombinant proteins and recently found ability of PARPs to attach the ADP-ribose moieties to DNA allowed us to attribute these products to primer mono(ADP-ribosyl)ation (MARylation) at the 5ʹ-terminal phosphate by PARP3 during the DNA synthesis. Under conditions of PAR synthesis, the efficiency of DNA synthesis was only slightly enhanced in all extracts and in mouse WCEs unusual products of the primer elongation were detected. The level of PAR synthesis was more than ten-fold higher in human WCE as compared to rodent WCEs, while the efficiency of DNA synthesis was comparable. Here, using the whole-cell extracts (WCEs) of Hgl, mouse and human cells, we studied the interrelation between DNA synthesis on the substrates of base excision repair and the activity of poly(ADP-ribose) polymerases (PARPs) responsible for the transfer of the ADP-ribose moieties onto different targets. DNA repair capacity in cells of naked mole rat (Hgl), a species known for its longevity and resistance to cancer, is still poorly characterized.
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