Mechanisms of mutagenesis for lambda phage
The principal experimental results are determination of the changes in DNA base sequence resulting from forward mutations in the cI (repressor) gene of lambda phage induced by various agents. For phage irradiated with ultraviolet light and assayed in lightly irradiated host cells to induce Weigle mutagenesis (targeted mutagenesis), two-thirds of the mutations are transitions. Most transitions seem to arise at the sites of Py(6-4)Pyo photoproducts, not at the more widely studied cyclobutane pyrimidine dimers. The other mutations induced by ultraviolet are equally divided among transversions, frameshifts and double mutation events. The latter, two closely spaced base changes or a base change plus a frameshift, should rarely revert and may be the deletions induced by ultraviolet which have been previously reported. Unirradiated phage assayed in host cells heavily irradiated with ultraviolet light (nontargeted mutagenesis) show mainly frameshift mutations. These frameshifts may arise from low intracellular activity of DNA polymerase I when the enzyme binds to host DNA damaged by irradiation of the cells. Mismatch repair greatly reduced the numbers of mutations from bromouracil (which induces transitions by base mispairing) and acridines which induce frameshifts at runs of G.C base pairs). Only when mismatch repair activity is saturated by the number of improperly stacked bases in the DNA does a high level of mutagenesis occur.
- Research Organization:
- Yale Univ., New Haven, CT
- OSTI ID:
- 6539528
- Journal Information:
- UCLA Symp. Mol. Cell. Biol., New Ser.; (United States), Vol. 11
- Country of Publication:
- United States
- Language:
- English
Similar Records
Effects of radiations on DNA and repair of the damage. Progress report, May 1, 1974--June 30, 1977. [Gamma and UV radiation, Escherichia coli, lambda phage]
Effects of radiations on DNA and repair of the damage. Progress report, May 1, 1976--March 31, 1977. [Escherichia coli, gamma radiation, UV radiation]
Related Subjects
BACTERIOPHAGES
BIOASSAY
MUTAGENESIS
DNA
BIOLOGICAL REPAIR
DAMAGE
ENZYME ACTIVITY
PHOTOCHEMICAL REACTIONS
POLYMERASES
ULTRAVIOLET RADIATION
BIOLOGICAL RECOVERY
CHEMICAL REACTIONS
ELECTROMAGNETIC RADIATION
ENZYMES
MICROORGANISMS
NUCLEIC ACIDS
NUCLEOTIDYLTRANSFERASES
ORGANIC COMPOUNDS
PARASITES
PHOSPHORUS-GROUP TRANSFERASES
RADIATIONS
RECOVERY
REPAIR
TRANSFERASES
VIRUSES
560121* - Radiation Effects on Cells- External Source- (-1987)