title: [Repair of bleomycin-induced damage to Escherichia coli DNA. I. Excision repair of apyrimidinic sites].
abstract: There are at least 4 endonucleolytic activities in Escherichia coli cells specific to apurinic and apyrimidinic sites in DNA. The main enzyme in the case of this type of DNA damage is believed to be an endonuclease VI responsible for 90% of total cell activity. Endonuclease VI is associated with exonuclease III which degrades DNA in 3'--5' direction. Our data indicate the absolute necessity of exonuclease III activity in repair of DNA containing apyrimidinic sites. It is possible that in the absence of endonuclease VI this type of DNA damage may be recognized by other endonucleases of E. coli--endonucleases III, V and especially endonuclease IV. During the postincubation of xthA mutant cells the normal molecular weight of DNA was not restored but even further DNA degradation was observed. DNA polymerase I takes part in DNA repair both in case of apyrimidinic sites and UV-induced pyrimidine dimers. Repair kinetics study showed partial molecular weight restoration in polA1 mutant. It is likely that in the absence of this enzyme some of its functions can be taken by other cell DNA polymerases.
mesh_terms: D001761:Bleomycin / Q000494:pharmacology*; D004256:DNA Polymerase I / Q000502:physiology*; D004260:DNA Repair; D004259:DNA-Directed DNA Polymerase / Q000502:physiology*; D004720:Endonucleases / Q000502:physiology*; D004926:Escherichia coli / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D005092:Exonucleases / Q000502:physiology*; D008970:Molecular Weight; D009154:Mutation; D013045:Species Specificity
chemical_list: D001761:Bleomycin; D004256:DNA Polymerase I; D004259:DNA-Directed DNA Polymerase; D004720:Endonucleases; D005092:Exonucleases
vernacular_title: Reparatsiia indutsirovannykh bleomitsinom povrezhdeniĭ DNK u Escherichia coli. Soobshchenie I. Ekstsizionnaia reparatsiia v otnoshenii apirimidinovykh saĭtov.