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Polymerase eta and p53 jointly regulate cell survival, apoptosis and Mre11 recombination during S phase checkpoint arrest after UV irradiation
- Source :
- DNA repair. 1(1)
- Publication Year :
- 2003
-
Abstract
- Xeroderma pigmentosum variant (XPV) cells lack the damage-specific polymerase eta and undergo a protracted arrest at the S phase checkpoint(s) following UV damage. The S phase checkpoints encompass several qualitatively different processes, and stimulate downstream events that are dependent on the functional state of p53. Primary fibroblasts with wild-type p53 arrest in S, and require a functional polymerase eta (pol eta) to carry out bypass replication, but do not recruit recombination factors for recovery. XPV cells with non-functional p53, as a result of transformation by SV40 or HPV16 (E6/E7), recruit the hMre11/hRad50/Nbs1 complex to arrested replication forks, coincident with PCNA, whereas normal transformed cells preferentially use the pol eta bypass replication pathway. The formation of hMre11 foci implies that arrested replication forks rapidly undergo a collapse involving double strand breakage and rejoining. Apoptosis occurs after UV only in cells transformed by SV40, and not in normal or XPV fibroblasts or HPV16 (E6/E7) transformed cells. Conversely, ultimate cell survival in XPV cells was much less in HPV16 (E6/E7) transformed cells than in SV40 transformed cells, indicating that apoptosis was not a reliable predictor of cell survival. Inhibition of p53 transactivation by pifithrin-alpha or inhibition of protein synthesis by cycloheximide did not induce hMre11 foci or apoptosis in UV damaged fibroblasts. Inhibition of kinase activity with wortmannin did not increase killing by UV, unlike the large increase seen with caffeine. Since HPV16 (E6/E7) transformed XPV cells were highly UV sensitive and not further sensitized by caffeine, it appears likely that caffeine sensitization proceeds through a p53 pathway. The S phase checkpoints are therefore, a complex set of different checkpoints that are coordinated by p53 with the capacity to differentially modulate cell survival, apoptosis, bypass replication and hMre11 recombination.
- Subjects :
- DNA Replication
Xeroderma pigmentosum
Cell Survival
Ultraviolet Rays
Blotting, Western
Apoptosis
Cell Cycle Proteins
DNA-Directed DNA Polymerase
Simian virus 40
Cycloheximide
Biochemistry
S Phase
Wortmannin
chemistry.chemical_compound
medicine
Humans
Benzothiazoles
Kinase activity
Molecular Biology
Cell Line, Transformed
Recombination, Genetic
MRE11 Homologue Protein
biology
Nuclear Proteins
Cell Biology
Oncogene Proteins, Viral
Cell cycle
Fibroblasts
medicine.disease
beta-Galactosidase
Molecular biology
Proliferating cell nuclear antigen
Acid Anhydride Hydrolases
DNA-Binding Proteins
Thiazoles
DNA Repair Enzymes
chemistry
Cell culture
biology.protein
Tumor Suppressor Protein p53
Toluene
Subjects
Details
- ISSN :
- 15687864
- Volume :
- 1
- Issue :
- 1
- Database :
- OpenAIRE
- Journal :
- DNA repair
- Accession number :
- edsair.doi.dedup.....d94bd82db3c536001b03dd6a9d270190