Repair of damaged DNA in vivo. Annual progress report, May 9, 1975--May 10, 1976. [Ultraviolet radiation, Escherichia coli]
PolA1 mutants of E. coli deficient in DNA polymerase I are sensitive to ultraviolet (UV) and have been shown to perform increased repair synthesis compared to pol/sup +/ strains. We have interpreted this result as an increase in a large patch component of repair synthesis. Both polymerases II and III are also capable of performing repair replication and could account for this synthesis. PolA1 mutants have nearly normal levels of the 5' ..-->.. 3' exonuclease and perform dimer excision at only slightly reduced rates. We have examined several mutants deficient in the 5' ..-->.. 3' exonuclease; The 5' ..-->.. 3' exonuclease deficient mutants polAex1 and polAex2 isolated by Konrad and Lehman, and polA107 of Glickman, and the conditionally-lethal mutant BT4113ts of Olivera and Bonhoeffer, deficient in both polymerizing and exonuclease activity at the restrictive temperature. These strains all perform increased repair synthesis relative to that in a pol/sup +/ strain. The UV sensitivity of the ex1 and ex2 mutants is intermediate between that of polA1 and pol/sup +/, and there is only a slight stimulation of UV-induced DNA degradation in these mutants, compared to extensive degradation in polA1 and BT4113ts. The enhancement of repair synthesis in the 5' ..-->.. 3' exonuclease-deficient mutants is less than in polA1, while the doubly deficient mutant BT4223ts shows even more repair synthesis than a polA1 strain. We are examining the dimer excision capabilities of the various strains and have found that the polAex2 mutant does excise dimers. We conclude that other enzymes can substitute for polymerase I in both the excision and resynthesis steps of excision-repair and that the resultant repair patches are of larger average size.
- Research Organization:
- Stanford Univ., CA (USA). Herrin Labs.
- OSTI ID:
- 7212851
- Report Number(s):
- SU-326P7-29
- Country of Publication:
- United States
- Language:
- English
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Role of DNA polymerase I in excision-repair
Deoxyribonucleic acid repair in Escherichia coli mutants deficient in the 5'----3' exonuclease activity of deoxyribonucleic acid polymerase I and exonuclease VII
Related Subjects
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
BACTERIA
BIOLOGICAL EFFECTS
BIOLOGICAL RADIATION EFFECTS
BIOLOGICAL RECOVERY
BIOLOGICAL REPAIR
BIOSYNTHESIS
DNA
ELECTROMAGNETIC RADIATION
ENZYMES
ESCHERICHIA COLI
METABOLISM
MICROORGANISMS
MUTANTS
NUCLEASES
NUCLEIC ACIDS
ORGANIC COMPOUNDS
PHOSPHOTRANSFERASES
POLYMERASES
RADIATION EFFECTS
RADIATIONS
RECOVERY
REPAIR
SYNTHESIS
TRANSFERASES
ULTRAVIOLET RADIATION