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Exonuclease III and endonuclease IV remove 3' blocks from DNA synthesis primers in H2O2-damaged Escherichia coli.
- Source :
-
Proceedings of the National Academy of Sciences of the United States of America [Proc Natl Acad Sci U S A] 1986 Oct; Vol. 83 (20), pp. 7731-5. - Publication Year :
- 1986
-
Abstract
- Escherichia coli deficient in exonuclease III (xth gene mutants) are known to be hypersensitive to hydrogen peroxide. We now show that such mutants accumulate many more DNA single-strand breaks than do wild-type bacteria upon exposure to H2O2. DNA isolated from H2O2-treated xth- cells contains strand breaks that do not efficiently support synthesis by E. coli DNA polymerase I, indicating the presence of blocking groups at the DNA 3' termini. Purified E. coli exonuclease III activates this blocked DNA to allow substantial synthesis by polymerase I in vitro. Another E. coli enzyme, endonuclease IV, also activates primers for DNA polymerase. Exonuclease III accounts for greater than 95% of the total activity in E. coli crude extracts for removal of 3'-terminal phosphoglycolaldehyde esters from model DNA substrates. Purified exonuclease III and endonuclease IV can each efficiently remove 3'-terminal phosphoglycolaldehyde in vitro. An important physiological function for exonuclease III is thus the activation of blocked 3' ends for DNA repair synthesis. Endonuclease IV can also initiate the repair of ruptured 3'-deoxyribose in DNA.
- Subjects :
- DNA, Bacterial biosynthesis
DNA, Bacterial drug effects
DNA, Bacterial radiation effects
DNA-(Apurinic or Apyrimidinic Site) Lyase
Deoxyribonuclease IV (Phage T4-Induced)
Endodeoxyribonucleases analysis
Escherichia coli metabolism
Exodeoxyribonucleases analysis
Exodeoxyribonucleases genetics
Mutation
DNA Damage
DNA Repair
Endodeoxyribonucleases pharmacology
Escherichia coli Proteins
Exodeoxyribonucleases pharmacology
Hydrogen Peroxide pharmacology
Subjects
Details
- Language :
- English
- ISSN :
- 0027-8424
- Volume :
- 83
- Issue :
- 20
- Database :
- MEDLINE
- Journal :
- Proceedings of the National Academy of Sciences of the United States of America
- Publication Type :
- Academic Journal
- Accession number :
- 2429316
- Full Text :
- https://doi.org/10.1073/pnas.83.20.7731