The role of DNA polymerase beta in determining sensitivity to ionizing radiation in human tumor cells.
Lethal lesions after ionizing radiation are thought to be mainly unrepaired or misrepaired DNA double-strand breaks, ultimately leading to lethal chromosome aberrations. However, studies with radioprotectors and repair inhibitors indicate that single-strand breaks, damaged nucleotides or abasic sites can also influence cell survival. This paper reports on studies to further define the role of base damage and base excision repair on the radiosensitivity of human cells. We retrovirally transduced human tumor cells with a dominant negative form of DNA polymerase beta, comprising the 14 kDa DNA-binding domain of DNA polymerase beta but lacking polymerase function. Radiosensitization of two human carcinoma cell lines, A549 and SQD9, was observed, achieving dose enhancement factors of 1.5-1.7. Sensitization was dependent on expression level of the dominant negative and was seen in both single cell clones and in unselected virally transduced populations. Sensitization was not due to changes in cell cycle distribution. Little or no sensitization was seen in G(1)-enriched populations, indicating cell cycle specificity for the observed sensitization. These results contrast with the lack of effect seen in DNA polymerase beta knockout cells, suggesting that polDN also inhibits the long patch, DNA polymerase beta-independent repair pathway. These data demonstrate an important role for BER in determining sensitivity to ionizing radiation and might help identify targets for radiosensitizing tumor cells.
Vens
Conchita
C
Division of Experimental Therapy and Department of Radiotherapy, The Netherlands Cancer Institute, 1066 CX Amsterdam, The Netherlands.
Dahmen-Mooren
Els
E
Verwijs-Janssen
Manon
M
Blyweert
Wim
W
Graversen
Lise
L
Bartelink
Harry
H
Begg
Adrian C
AC
D002453:Cell Cycle / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D002455:Cell Division / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D002467:Cell Nucleus / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects*; D019951:DNA Polymerase beta / Q000235:genetics / Q000502:physiology*; D016193:G1 Phase / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D015971:Gene Expression Regulation, Enzymologic; D049452:Green Fluorescent Proteins; D006801:Humans; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D008769:Methylnitronitrosoguanidine / Q000494:pharmacology; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured / Q000528:radiation effects; D014466:Ultraviolet Rays
D008164:Luminescent Proteins; D011993:Recombinant Fusion Proteins; D008769:Methylnitronitrosoguanidine; D049452:Green Fluorescent Proteins; D019951:DNA Polymerase beta