Interaction of benzo(a)pyrene-7,8-dihydrodiol-9,10-oxide with simian virus 40 DNA and chromatin

Technical Report · Thu Nov 01 04:00:00 EST 1979

OSTI ID:5732415

Gamper, Jr, H B

In mammalian cells, benzo(a)pyrene undergoes metabolic activation to the ultimate carcinogen benzo(a)pyrene-7,8-dihydrodiol-9,10-oxide (BaP diol epoxide). The conformation of simian virus 40 (SV40) DNA and chromatin reacted in vitro with BaP diol epoxide was studied. Nicking of superhelical SV40 DNA was monitored. Approximately 1% of the initial BaP diol epoxide alkylation sites rearranged with strand scission at pH 8.0. This strand scission was due to one or more minor alkylation products. The kinetics of nicking were characteristic of a multistep rearrangement terminating in strand scission. No evidence was obtained for nicking proceeding through a phosphotriester mechanism. The superhelical density of BaP diol epoxide modified superhelical and partially relaxed SV40 DNA was determined and an unwinding angle for the hydrocarbon guanine adduct was calculated. The anlge was dependent upon the torsional strain of the molecule. This data indicated that the modified G-C base pair was disrupted. In the absence of such strain the alkylation sites had an ordered structure with the hydrocarbon oriented in the minor or major groove of the helix. Although BaP diol epoxide adducts were externally bound, the hydrocarbon appeared to intercalate prior to reaction with the exocyclic amino group of guanine. Thus, covalent binding was modulated by helix stability. Counterions inhibited alkylation by up to 90%, Mg/sup 2 +/ being more effective than Na/sup +/, and superhelical SV40 DNA more susceptible than partially relaxed viral DNA. The alkylation of SV40 minichromosomes was also investigated. Relative to protein-free SV40 DNA, minichromosomal DNA was 1.5X less susceptible to alkylation but 2X more prone to strand scission. The alkylation of minichromosomal DNA was random. (ERB)

• Research Organization: California Univ., Berkeley (USA). Lawrence Berkeley Lab.
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 5732415
• Report Number(s): LBL-10096
• Country of Publication: United States
• Language: English

Related Subjects

550200 -- Biochemistry
560301* -- Chemicals Metabolism & Toxicology-- Cells-- (-1987)
59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ALKYLATION
AROMATICS
BENZOPYRENE
BIOLOGICAL EFFECTS
CARCINOGENS
CHEMICAL REACTIONS
CHROMATIN
CONDENSED AROMATICS
CONFORMATIONAL CHANGES
DATA
DATA FORMS
DNA
EPOXIDES
EXPERIMENTAL DATA
HYDROCARBONS
INFORMATION
ISOLATED VALUES
METABOLIC ACTIVATION
METABOLITES
MICROORGANISMS
NUCLEIC ACIDS
NUMERICAL DATA
ORGANIC COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
PARASITES
STRAND BREAKS
VIRUSES