Effect of the uvs-2 allele of Neurospora crassa on the mutagenic potency of two N-hydroxylaminopurines and 2-aminopurine in the ad-3 forward-mutation test.
The mutagenic potencies of 3 purine analogs were determined in the ad-3 forward-mutation test in growing cultures of heterokaryon 59 (H-59), a nucleotide excision repair-deficient (uvs-2/uvs-2) 2-component heterokaryon of Neurospora crassa. Two N-hydroxylaminopurines, 2-amino-6-N-hydroxylaminopurine (AHA) and 6-N-hydroxylaminopurine (HAP), were potent and strong mutagens, respectively, whereas 2-aminopurine (AP) was a moderate mutagen. Dose-response curves showed that AHA and HAP were about equally mutagenic at low doses but that AHA was more mutagenic than HAP at high doses. Comparison of these results in H-59 with our earlier results in heterokaryon 12 (H-12) of N. crassa, which is identical to H-59 except for being DNA-repair-proficient (uvs-2+/uvs-2+), shows that the defect in nucleotide excision repair due to uvs-2 has little or no effect on the mutagenic potencies of these 3 purine analogs. Therefore, the nucleotide excision-repair pathway in N. crassa that is deficient in H-59 does not appear to have a major role in the repair of pre-mutational lesions induced by these 3 purine analogs. On the other hand, based on the controls of these experiments, the frequency of spontaneous ad-3 mutants was 4 greater in H-59 than in H-12. This result suggests that the nucleotide excision-repair pathway in N. crassa that is inactivated by the uvs-2 mutation has a major role in the repair of lesions that would lead to spontaneous mutation at the ad-3+ region if they were not repaired.
Brockman
H E
HE
Department of Biological Sciences, Illinois State University, Normal 61761.
de Serres
F J
FJ
Hung
C Y
CY
Ong
T
T
D015075:2-Aminopurine / Q000633:toxicity*; D000225:Adenine / Q000031:analogs & derivatives* / Q000633:toxicity; D000483:Alleles; D004260:DNA Repair; D005800:Genes, Fungal; D009152:Mutagenicity Tests; D009153:Mutagens; D009154:Mutation; D009491:Neurospora / Q000235:genetics*; D009492:Neurospora crassa / Q000235:genetics*
D009153:Mutagens; D015075:2-Aminopurine; C032610:6-N-hydroxylaminopurine; C030632:2-amino-N(6)-hydroxyadenine; D000225:Adenine