title: DNA double strand break repair enzymes function at multiple steps in retroviral infection.
abstract: BACKGROUND
  DNA double strand break (DSB) repair enzymes are thought to be necessary for retroviral infection, especially for the post-integration repair and circularization of viral cDNA. However, the detailed roles of DSB repair enzymes in retroviral infection remain to be elucidated.
  
  
  RESULTS
  A GFP reporter assay showed that the infectivity of an HIV-based vector decreased in ATM- and DNA-PKcs-deficient cells when compared with their complemented cells, while that of an MLV-based vector was diminished in Mre11- and DNA-PKcs-deficient cells. By using a method based on inverse- and Alu-PCR, we analyzed sequences around 3' HIV-1 integration sites in ATM-, Mre11- and NBS1- deficient cells. Increased abnormal junctions between the HIV-1 provirus and the host DNA were found in these mutant cell lines compared to the complemented cell lines and control MRC5SV cells. The abnormal junctions contained two types of insertions: 1) GT dinucleotides, which are normally removed by integrase during integration, and 2) inserted nucleotides of unknown origin. Artemis-deficient cells also showed such abnormalities. In Mre11-deficient cells, part of a primer binding site sequence was also detected. The 5' host-virus junctions in the mutant cells also contained these types of abnormal nucleotides. Moreover, the host-virus junctions of the MLV provirus showed similar abnormalities. These findings suggest that DSB repair enzymes play roles in the 3'-processing reaction and protection of the ends of viral DNA after reverse transcription. We also identified both 5' and 3' junctional sequences of the same provirus by inverse PCR and found that only the 3' junctions were abnormal with aberrant short repeats, indicating that the integration step was partially impaired in these cells. Furthermore, the conserved base preferences around HIV-1 integration sites were partially altered in ATM-deficient cells.
  
  
  CONCLUSIONS
  These results suggest that DSB repair enzymes are involved in multiple steps including integration and pre-integration steps during retroviral replication.
authors.affiliation: Institute for Virus Research, Kyoto University, Sakyo-ku, Kyoto, Japan. ysakurai@virus.kyoto-u.ac.jp
authors.forename: Yasuteru
authors.initials: Y
authors.lastname: Sakurai
authors.forename: Kenshi
authors.initials: K
authors.lastname: Komatsu
authors.forename: Kazunaga
authors.initials: K
authors.lastname: Agematsu
authors.forename: Masao
authors.initials: M
authors.lastname: Matsuoka
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins; D001483:Base Sequence; D018797:Cell Cycle Proteins; D002460:Cell Line; D004247:DNA / Q000032:analysis / Q000235:genetics / Q000378:metabolism; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair; D051747:DNA-Activated Protein Kinase / Q000172:deficiency; D004268:DNA-Binding Proteins / Q000172:deficiency; D004720:Endonucleases; D015894:Genome, Human; D015658:HIV Infections / Q000201:enzymology* / Q000821:virology; D015497:HIV-1 / Q000502:physiology*; D054884:Host-Pathogen Interactions / Q000235:genetics; D006801:Humans; D000076228:MRE11 Homologue Protein; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000172:deficiency; D017346:Protein Serine-Threonine Kinases / Q000172:deficiency; D025521:Tumor Suppressor Proteins / Q000172:deficiency; D016662:Virus Integration; D014779:Virus Replication
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C121766:MRE11 protein, human; C112156:NBN protein, human; D009687:Nuclear Proteins; D025521:Tumor Suppressor Proteins; D004247:DNA; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D051747:DNA-Activated Protein Kinase; D017346:Protein Serine-Threonine Kinases; C426344:DCLRE1C protein, human; D004720:Endonucleases; D000076228:MRE11 Homologue Protein