title: Mutations induced by methylene blue plus light in single-stranded M13mp2.
abstract: Reactive oxygen species are generated by a variety of cellular processes. These endogenously generated, reactive intermediates produce a multiplicity of DNA alterations and mutations and have been implicated in the pathogenesis of several human diseases. We report here that treatment of single-stranded M13mp2 bacteriophage DNA with methylene blue and white light generates increased levels of 8-hydroxydeoxyguanosine and that mutagenesis is both highly specific and dependent on the SOS response. Lesions produced block the progression of DNA synthesis one base preceding template guanines. In SOS-induced Escherichia coli, 97% of all methylene blue-induced mutations in the lacZ alpha gene of M13mp2 DNA are single-base substitutions opposite template guanines. The most frequent mutations are G----C transversions. The G----T transversions expected from the presence of 8-hydroxydeoxyguanosine in the template strand occur, but at a lower frequency. Sequence data together with SOS dependency and the presence of replication blockage demonstrate that while 8-hydroxydeoxyguanosine may serve as an important marker to monitor oxygen-induced DNA damage in humans, it does not account for either the observed blockage to replication or the mutagenesis by methylene blue plus light in SOS-induced E. coli. Instead, an as yet unidentified lesion generated by active oxygen species is a more potent mutagenic event.
authors.affiliation: Joseph Gottstein Memorial Cancer Research Laboratory, Department of Pathology, University of Washington, Seattle 98195.
authors.forename: T J
authors.initials: TJ
authors.lastname: McBride
authors.forename: J E
authors.initials: JE
authors.lastname: Schneider
authors.forename: R A
authors.initials: RA
authors.lastname: Floyd
authors.forename: L A
authors.initials: LA
authors.lastname: Loeb
mesh_terms: D000080242:8-Hydroxy-2'-Deoxyguanosine; D001483:Base Sequence; D003090:Coliphages / Q000187:drug effects / Q000235:genetics* / Q000528:radiation effects; D004269:DNA, Bacterial / Q000187:drug effects / Q000235:genetics / Q000528:radiation effects; D004277:DNA, Single-Stranded / Q000187:drug effects / Q000235:genetics* / Q000528:radiation effects; D003849:Deoxyguanosine / Q000031:analogs & derivatives* / Q000032:analysis; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics* / Q000528:radiation effects; D008027:Light; D008751:Methylene Blue / Q000494:pharmacology*; D008969:Molecular Sequence Data; D016296:Mutagenesis; D013014:SOS Response, Genetics; D014162:Transfection
chemical_list: D004269:DNA, Bacterial; D004277:DNA, Single-Stranded; D000080242:8-Hydroxy-2'-Deoxyguanosine; D003849:Deoxyguanosine; D008751:Methylene Blue