Involvement of DNA polymerase mu in the repair of a specific subset of DNA double-strand breaks in mammalian cells.
The repair of DNA double-strand breaks (DSB) requires processing of the broken ends to complete the ligation process. Recently, it has been shown that DNA polymerase mu (polmu) and DNA polymerase lambda (pollambda) are both involved in such processing during non-homologous end joining in vitro. However, no phenotype was observed in animal models defective for either polmu and/or pollambda. Such observations could result from a functional redundancy shared by the X family of DNA polymerases. To avoid such redundancy and to clarify the role of polmu in the end joining process, we generated cells over-expressing the wild type as well as an inactive form of polmu (polmuD). We observed that cell sensitivity to ionizing radiation (IR) was increased when either polmu or polmuD was over-expressed. However, the genetic instability in response to IR increased only in cells expressing polmuD. Moreover, analysis of intrachromosomal repair of the I-SceI-induced DNA DSB, did not reveal any effect of either polmu or polmuD expression on the efficiency of ligation of both cohesive and partially complementary ends. Finally, the sequences of the repaired ends were specifically affected when polmu or polmuD was over-expressed, supporting the hypothesis that polmu could be involved in the repair of a DSB subset when resolution of junctions requires some gap filling.
Capp
Jean-Pascal
JP
Genetic instability and Cancer group, Institute of Pharmacology and Structural Biology, University Paul Sabatier, UMR CNRS 5089, 205 route de Narbonne, 31077 Toulouse cedex, France.
Boudsocq
François
F
Besnard
Anne-Gaelle
AG
Lopez
Bernard S
BS
Cazaux
Christophe
C
Hoffmann
Jean-Sébastien
JS
Canitrot
Yvan
Y
D000818:Animals; D001483:Base Sequence; D016466:CHO Cells; D002460:Cell Line; D002869:Chromosome Aberrations; D006224:Cricetinae; D003412:Cricetulus; D004247:DNA / Q000737:chemistry; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair; D004259:DNA-Directed DNA Polymerase / Q000502:physiology*; D015252:Deoxyribonucleases, Type II Site-Specific / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D011839:Radiation, Ionizing; D029701:Saccharomyces cerevisiae Proteins
D029701:Saccharomyces cerevisiae Proteins; D004247:DNA; C407743:DNA polymerase mu; D004259:DNA-Directed DNA Polymerase; C037725:SCEI protein, S cerevisiae; D015252:Deoxyribonucleases, Type II Site-Specific