The long-term goal of this investigation is to understand mechanisms of mutagenesis during the replication of damaged DNA. Ultraviolet(UV) irradiation of single strand DNA phage and phage DNA is used to provide DNA containing premutagenic lesions; phage DNA replication, carried out in vivo or in vitro, provides a system for studying the response of DNA replication proteins to specific damage in DNA and the induction of mutations that may be consequence of replicating lesion-containing DNA. The primary aim of this application is to develop the use of the M131ac hybrid phage, a single-strand DNA bacteriophage carrying a portion of the E. coli lactose operon, as a forward mutation system for studying UV mutagenesis in vivo and in vitro. Infection of E. coli with UV-irradiated m131ac phage allows detection of mutated phage with a lac- phenotype. This mutagenesis is enhanced (10-fold) by infection of host cells that have been induced for error-prone DNA replication and repair by UV irradiation prior to infection. Mutant clones are amenable to direct nucleotide sequencing to determine sites of misincorporation during replication of UV-irradiated DNA and to assess the contribution of a host error-prone replication apparatus to UV mutagenesis. Experiments are proposed for using the M131ac phage DNA in an in vitro system for DNA replication and determination of mutation induction by transfection assays. The proposed experiments are a basis for studying the biochemical reactions that give rise to mutations during replication of damaged DNA templates. This relatively simple system will yield information on mechanisms of mutagenesis that are part of an inefficent recovery system for phage and bacteria, but may be very significant to induction of carcinogenesis in mammalian cells.
