| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1987: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1986: ¥1,400,000 (Direct Cost: ¥1,400,000)
|
|---|
| Research Abstract |
M. luteus mutants showing increased sensitivity to both UV and 4-NQO were isolated after the treatment of parental ATCC4698 strain with MNNG. The mutants were also highly sensitive to mitomycin C, cis-platinum, 8-methoxypsoralen (8-MOP) plus near-UV and angelicin plus near-UV in various degrees. The endonuclease activity specific for pyrimidine dimers in UV-irradiated DNA was normally detected in extract of the mutants. With regard to host-cell reactivation ability the mutants fell into two groups. The hcr^- mutants lacked the ability to reactivate UV-damaged N6 phage and were resistant to X-rays. The incision of DNA did not occur during incubation after the treatment with angelicin plus near-UV in the hcr^- mutants, whereas it occurred in the parental strain. The facts indicate that the hcr mutants are defective in the incision mechanism which has a wide substrate specificity, similar to the UVRABC nuclease of E. coli. On the other hand, the incision of DNA and the removal of UV-induced thymine dimers form DNA occurred in the hcr^- mutants as well as in the parental strain, which is ascribed to the UV endonuclease activity. Compared with the hcr^- mutants, hcr^+ mutants were highly sensitive to X-rays and showed no induction of erythromycin-resistant mutation due to UV, like recA^- mutants of E. coli.
|
