DNA polymerase X from Deinococcus radiodurans implicated in bacterial tolerance to DNA damage is characterized as a short patch base excision repair polymerase.
The Deinococcus radiodurans R1 genome encodes an X-family DNA repair polymerase homologous to eukaryotic DNA polymerase beta. The recombinant deinococcal polymerase X (PolX) purified from transgenic Escherichia coli showed deoxynucleotidyltransferase activity. Unlike the Klenow fragment of E. coli, this enzyme showed short patch DNA synthesis activity on heteropolymeric DNA substrate. The recombinant enzyme showed 5'-deoxyribose phosphate (5'-dRP) lyase activity and base excision repair function in vitro, with the help of externally supplied glycosylase and AP endonuclease functions. A polX disruption mutant of D. radiodurans expressing 5'-dRP lyase and a truncated polymerase domain was comparatively less sensitive to gamma-radiation than a polX deletion mutant. Both mutants showed higher sensitivity to hydrogen peroxide. Excision repair mutants of E. coli expressing this polymerase showed functional complementation of UV sensitivity. These results suggest the involvement of deinococcal polymerase X in DNA-damage tolerance of D. radiodurans, possibly by contributing to DNA double-strand break repair and base excision repair.
Khairnar
Nivedita P
NP
Molecular Biology Division, Bhabha Atomic Research Centre, Mumbai-400 085, India.
Misra
Hari S
HS
Molecular Biology Division, Bhabha Atomic Research Centre, Mumbai-400 085, India.
D000251:Adenosine Triphosphatases / Q000172:deficiency / Q000235:genetics; D003432:Cross-Linking Reagents / Q000009:adverse effects; D053903:DNA Breaks, Double-Stranded; D045647:DNA Glycosylases / Q000172:deficiency / Q000235:genetics; D004253:DNA Nucleotidylexotransferase / Q000378:metabolism; D004260:DNA Repair; D004269:DNA, Bacterial / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D004268:DNA-Binding Proteins / Q000172:deficiency / Q000235:genetics; D004259:DNA-Directed DNA Polymerase / Q000235:genetics / Q000378:metabolism*; D034301:Deinococcus / Q000201:enzymology* / Q000235:genetics / Q000528:radiation effects*; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D029968:Escherichia coli Proteins / Q000235:genetics; D005720:Gamma Rays / Q000009:adverse effects; D005816:Genetic Complementation Test; D016685:Mitomycin / Q000009:adverse effects; D018384:Oxidative Stress; D019761:Phosphorus-Oxygen Lyases / Q000378:metabolism; D014466:Ultraviolet Rays / Q000009:adverse effects
D003432:Cross-Linking Reagents; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D029968:Escherichia coli Proteins; D016685:Mitomycin; C423906:5'-deoxyribose phosphate lyase; C109534:DNA polymerase X; D004253:DNA Nucleotidylexotransferase; D004259:DNA-Directed DNA Polymerase; D045647:DNA Glycosylases; C076131:DNA-3-methyladenine glycosidase II; C068631:UvrA protein, E coli; D000251:Adenosine Triphosphatases; D019761:Phosphorus-Oxygen Lyases