Excision Repair Characteristics of recB−res− and uvrC− Strains of Escherichia coli
AUTOR(ES)
Kato, Takesi
RESUMO
An Escherichia coli strain carrying the recB21 and res-1 mutations showed an abnormally low level of colony-forming ability although it grew essentially normally in liquid medium. The recB21 res-1 strain showed little, if any, of the ultraviolet (UV)-induced deoxyribonucleic acid (DNA) breakdown characteristic of the res-1 mutant. Nevertheless, the double mutant was far more sensitive to UV than either the res-1 or the recB21 strain. When compared with a wild-type strain, the rate of release of dimers from UV-irradiated DNA was very slow in the recB21 res-1, but normal in the res-1 recB+ or recB21 res+ mutants. However, the ratio of dimer-to-thymine released into the acid-soluble fraction was three times higher than the wild type in recB21 res+ and recB21 res-1 and only one-tenth as high as the wild type in res-1 rec+. Alkaline sucrose gradient centrifugation revealed occurrence of single-strand incision of UV-irradiated DNA and the restitution of nicked DNA at a similar rate in the recB21 res-1 and recB21 res+ strains. Mutants uvrC− showed increased amounts of nicks in their DNA with increasing incubation time after UV irradiation, although no detectable amounts of dimers were excised from UV-irradiated DNA. From these results, it is concluded that the increased sensitivity of the res-1 strain to UV light is due to a reduced ability to excise dimers from UV-irradiated DNA and that the high rate of UV-induced breakdown of DNA is not the primary cause. A possible role of uvrC gene in the excision repair is discussed.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=251554Documentos Relacionados
- uvrC Gene Function in Excision Repair in Toluene-Treated Escherichia coli
- The C-terminal region of Escherichia coli UvrC contributes to the flexibility of the UvrABC nucleotide excision repair system
- Regulation of the Escherichia coli excision repair gene uvrC. Overlap between the uvrC structural gene and the region coding for a 24 kD protein.
- Single-strand breakage of DNA in UV-irradiated uvrA, uvrB, and uvrC mutants of Escherichia coli.
- Cloning of the uvrC gene of Escherichia coli: expression of a DNA repair gene.