Comparative study of the lethal effects of near-UV light (360 nm) and 8-methoxypsoralen plus near-UV on plasmid DNA.
We have studied the lethality produced on pBR322 by near-UV radiation and by 8-Methoxypsoralen plus near-UV (PUV treatment). Samples of pBR322 DNA were irradiated with increasing fluences of 360 nm-light either in the absence or presence of 400 molecules of 8-Methoxypsoralen (8-MOP) per plasmid molecule. We have estimated to what extent the global lethality of PUVA treatment is due to the presence of psoralen adducts in DNA or to radiation itself. In order to analyse the involvement of DNA repair mechanisms in the removal of plasmid lesions, several strains of E. coli (differing in their repair capacities) were used as recipients of the treated plasmids. Results showed that excision and recombination participate in the repair of near-UV-induced plasmid lesions. Repair of PUV-induced lesions showed an even greater requirement of the excision pathway. Besides, a slight increase on plasmid mutation frequencies was observed after near-UV or PUV treatment in wild type and uvrA cells. Estimation of the contribution of 8-MOP to the global lethality of PUV treatment showed that only the excision pathway was involved in removing psoralen adducts from plasmid DNA, suggesting the involvement of the recombinational pathway in the repair of near-UV-derived lesions.
Paramio
J M
JM
Unidad de Biología Molecular, CIEMAT, Madrid, Spain.
Bauluz
C
C
de Vidania
R
R
D004249:DNA Damage; D004260:DNA Repair; D004269:DNA, Bacterial / Q000187:drug effects* / Q000528:radiation effects; D004926:Escherichia coli / Q000235:genetics; D008730:Methoxsalen / Q000494:pharmacology*; D016296:Mutagenesis; D010957:Plasmids / Q000187:drug effects* / Q000528:radiation effects; D013014:SOS Response, Genetics; D014466:Ultraviolet Rays
D004269:DNA, Bacterial; D008730:Methoxsalen