title: Molecular analysis of ethyl methanesulfonate-induced mutations at the hprt gene in the ethyl methanesulfonate-sensitive Chinese hamster cell line EM-C11 and its parental line CHO9.
abstract: The Chinese hamster cell line EM-C11 has been shown to be 5 times more sensitive than its parental line CHO9, but not hypermutable, after treatment with ethyl methanesulfonate. Ethyl methanesulfonate-induced mutational spectra were determined at the hprt locus to investigate whether the same adducts are responsible for mutation induction in both cell lines. The mutational spectra for EM-C11 and CHO9 show an important difference. GC-->AT transitions were found in both cell lines at similar frequencies; however, the spectrum of CHO9 contains a class of AT-->GC transitions, which seems to be replaced by a group of deletions in EM-C11. Since the ethyl methanesulfonate-induced mutation frequency for both lines is the same at equal exposure, it is hypothesized that the lesions leading to AT-->GC transitions in CHO9 are responsible for the deletions in EM-C11. This phenomenon might be explained if the responsible adduct(s) in CHO9 is bypassed resulting in replication errors, while blocking DNA synthesis in EM-C11 causing the observed increase in cell death. In surviving EM-C11 cells, DNA strand exchanges might have occurred at the position of stalled replication forks, leading to gross molecular changes. The adduct probably responsible for the AT-->GC transitions in CHO9 and the deletions in EM-C11 is 3-ethyladenine.
authors.affiliation: MGC-Department of Radiation Genetics and Chemical Mutagenesis, State University of Leiden, The Netherlands.
authors.forename: C W
authors.initials: CW
authors.lastname: Op het Veld
authors.forename: M Z
authors.initials: MZ
authors.lastname: Zdzienicka
authors.forename: H
authors.initials: H
authors.lastname: Vrieling
authors.forename: P H
authors.initials: PH
authors.lastname: Lohman
authors.forename: A A
authors.initials: AA
authors.lastname: van Zeeland
mesh_terms: D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D003114:Colony-Forming Units Assay; D006224:Cricetinae; D003412:Cricetulus; D018076:DNA, Complementary / Q000235:genetics; D005020:Ethyl Methanesulfonate / Q000494:pharmacology*; D007041:Hypoxanthine Phosphoribosyltransferase / Q000235:genetics*; D008969:Molecular Sequence Data; D017354:Point Mutation / Q000235:genetics*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics
chemical_list: D018076:DNA, Complementary; D012333:RNA, Messenger; D005020:Ethyl Methanesulfonate; D007041:Hypoxanthine Phosphoribosyltransferase