Project Details


The long-term objective of this proposal is to elucidate the molecular
mechanisms by which environmental chemicals cause cancer. The specific
concentration in this project is on the mechanisms of mutagenesis by the
fungal metabolite aflatoxin B1, a common food contaminant and a suspected
human carcinogen. The experimental system primarily involves prokaryotic
model genomes (phase 0X174 and plasmid pBR322) although certain experiments
involve cultured primate cell lines. Both single and multiple AFB1 adducts
will be introduced into the model genomes using in vitro DNA manipulations
and their mutagenic consequences in vivo under selected repair conditions
will be studied. All mutational consequences in selected 0X genes will be
isolated by the strategy of plasmid-mediated complementation.
Representative mutants will be analyzed at the sequence level to answer the
following types of questions: (1) Are AFB1-induced DNA modifications
mutagenic? (2) If they are, what principal types of mutations are
produced? (3) Is there a positive correlation between site of AFB1 adduct
and mutation? (4) What are the mechanisms for the reported frameshift
mutagenesis by AFB1? If deletion of insertion, how many bases are involved
and are there pattern? Essentially similar questions will also be
addressed in a highly specific in vitro mutagenesis system. In addition,
we will examine certain aspects of the interaction of AFB1 with DNA in
vitro nd in vivo. Some of these experiments were suggested by our recent
finding that the rate of AFB1 modification of G residues is strongly and
predictably influenced by the sequence context. a) Are the in vitro
sequence-specific effects mimicked in vivo? b) How does DNA in chromatin
react with AFB1? c) Does AFB1 prefer actively expressed genes? d) How
does DNA superhelicity affect sequence specificity? and e) What is the
mechanistic basis for the specificity?
Effective start/end date5/1/844/30/89


  • National Institutes of Health
  • National Institutes of Health
  • National Institutes of Health
  • National Institutes of Health


  • Medicine(all)

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