DNA base changes and alkylation following in vivo exposure of Escherichia coli to N-methyl-N-nitrosourea or N-ethyl-N-nitrosourea

Journal Article · Thu Jan 01 00:00:00 EST 1987 · Proc. Natl. Acad. Sci. U.S.A.; (United States)

DOI:https://doi.org/10.1073/pnas.84.2.344· OSTI ID:6119573

Richardson, K K; Richardson, F C; Crosby, R M; Swenberg, J A; Skopek, T R

Dideoxy chain-termination DNA sequencing was used to determine the specific DNA base changes induced after in vivo exposure of Escherichia coli to N-methyl-N-nitrosourea (MNU) and N-ethyl-N-nitrosourea (ENU) using the xanthine guanine phosphoribosyltransferase (gpt) gene as the genetic target. The resultant mutation spectra were compared with the levels of O/sup 6/-alkylguanine and O/sup 4/-alkylthymidine in genomic DNA immediately after exposure. All (39/39) of the MNU-induced mutations were G x C ..-->.. A x T transition. In contrast, 24/33 point mutations isolated following ENU treatment were G x C ..-->.. A x T transitions, 7/33 were A x T ..-->.. G x C transitions, 1/33 was a G x C ..-->.. C x G transversion, and 1/33 was an A x T ..-->.. C x G transversion. Three large insertions, probably of spontaneous origin, were also isolated. O/sup 4/-alkylthymidine/O/sup 6/-alkylguanine ratios were 0.014 for MNU and 0.28 for ENU. These data suggest that the difference in the mutation spectrum of MNU versus ENU may be attributed, in part, to the different ratio of O/sup 6/-alkylguanine versus O/sup 4/-alkylthymidine produced in the DNA. Of the G x C ..-->.. A x T transitions, 82% of the MNU- and 71% of the ENU-induced mutations occurred at the middle guanine of the sequence 5'-GG(A or T)-3'.

• Research Organization: Chemical Industry Institute of Toxicology, Research Triangle Park, NC
• OSTI ID: 6119573
• Journal Information: Proc. Natl. Acad. Sci. U.S.A.; (United States), Vol. 84:2
• Country of Publication: United States
• Language: English

Related Subjects

63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
DNA
ALKYLATION
NITROSOUREAS
GENETIC EFFECTS
AMINO ACID SEQUENCE
DNA SEQUENCING
ESCHERICHIA COLI
GENE MUTATIONS
GENETIC MAPPING
HYPOXANTHINE PHOSPHORIBOSYLTRANSFERASE
IN VIVO
BACTERIA
BIOLOGICAL EFFECTS
CHEMICAL REACTIONS
ENZYMES
GLYCOSYL TRANSFERASES
MAPPING
MICROORGANISMS
MOLECULAR STRUCTURE
MUTATIONS
NITROSO COMPOUNDS
NUCLEIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PENTOSYL TRANSFERASES
STRUCTURAL CHEMICAL ANALYSIS
TRANSFERASES
560300* - Chemicals Metabolism & Toxicology