ISSN:
1617-4623
Keywords:
Neurospora crassa
;
Excision repair
;
UV mutagenesis
;
Liquid-holding recovery
;
Pyrimidine dimer
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Summary A UV-sensitive mutant has been isolated from UV-mutagenized conidia of Neurospora crassa. The mutation responsible for the lesion was mapped in linkage group VL, proximal to the nucleolus organizer region. We designated the mutant mus-18. The sensitivity of the mus-18 mutant to UV-irradiation was not particularly high, being less than twice that of the wild-type strain. However, the frequency of mutations at the ad-3 loci induced by UV was extremely high even at low doses, under conditions where survival rates of mus-18 cells were almost identical to those of wild-type cells. Photoreactivation of UV damage was normal in the mus-18 mutant. Sensitivity to other mutagens, such as gamma rays, 4-nitroquinoline-1-oxide, N-methyl-N′-nitro-N-nitrosoguanidine, mitomycin C and methyl methanesulfonate, was similar to that of the wild type. Fertility of the mus-18 mutant was normal in homozygous crosses. These results suggest that mus-18 is an excision-repair mutant. Measurement of endonuclease-sensitive sites (ESS) after liquid-holding recovery from UV damage revealed that ESS remained unrepaired for longer than 18 h in the mus-18 mutant, while most were eliminated within 6 h in wild-type cells and in other UV-sensitive mutants. This result suggests that mus-18 is defective in the incision step of dimer excision. The mus-18 mutant provides the first example of an excision-defective mutation in eukaryotes, which is specific to UV damage.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00282444
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