title: Ultraviolet reactivation and ultraviolet mutagenesis of infectious lambda DNA: strong inhibition by treatment of DNA in vitro with UV-endonuclease from Micrococcus  luteus.
abstract: UV-endonuclease from Microcossuc luteus induces single-stranded breaks in UV-irradiated DNA of phage lambda and the average length of the fragments produced (after UV-doses to DNA of 135 and 675 erg/mm2) is equal to the average spacing between pyrimidine dimers. The plaque-forming ability of UV-irradiated lambda DNA used to infect Ca++-treated uvr A6, uvrB5 or uvrC34 recipient Escherichia coli cells (but not uve+ cells) may be significantly enhanced by treatment of lambda DNA with UV-endonuclease. This enzyme strongly decreases the reactivation of UV-irradiated lambda DNA caused by UV-irradiation of uvr+ or uvrA6 Ca++-treated cells and eliminates most clear-mutations especially if mutations are analysed using Ca++-treated uvr A6 recipient cells. It is concluded that UV-endonuclease switches a significant part of potentially mutagenic pyrimidine dimers from the UV-induced "error-prone" repair pathway to "error-free" excision repair pathway.
mesh_terms: D002501:Centrifugation, Zonal; D003090:Coliphages / Q000528:radiation effects*; D004260:DNA Repair; D004261:DNA Replication; D004267:DNA Viruses / Q000528:radiation effects; D004279:DNA, Viral / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D004720:Endonucleases / Q000494:pharmacology*; D004926:Escherichia coli; D008837:Micrococcus / Q000201:enzymology*; D009154:Mutation; D011831:Radiation Genetics; D014466:Ultraviolet Rays
chemical_list: D004279:DNA, Viral; D004720:Endonucleases