aphidicolin and 2--deoxy-5--adenosine-monophosphate

Mutations in oncogenes and tumor suppressor genes are critical in the development of cancer. A major pathway for the formation of mutations is the replication of unrepaired DNA lesions. To better understand the mechanism of translesion replication (TLR) in mammals, a quantitative assay for TLR in cultured cells was developed. The assay is based on the transient transfection of cultured cells with a gapped plasmid, carrying a site-specific lesion in the gap region. Filling in of the gap by TLR is assayed in a subsequent bioassay, by the ability of the plasmid extracted from the cells, to transform an Escherichia coli indicator strain. Using this method it was found that TLR through a synthetic abasic site in the adenocarcinoma H1299, the osteogenic sarcoma Saos-2, the prostate carcinoma PC3, and the hepatoma Hep3B cell lines occurred with efficiencies of 92 +/- 6%, 32 +/- 2%, 72 +/- 4%, and 26 +/- 3%, respectively. DNA sequence analysis showed that 85% of the bypass events in H1299 cells involved insertion of dAMP opposite the synthetic abasic site. Addition of aphidicolin, an inhibitor of DNA polymerases alpha, delta, and epsilon, caused a 4.4-fold inhibition of bypass. Analysis of two XP-V cell lines, defective in DNA polymerase eta, showed bypass of 89%, indicating that polymerase eta is not essential for bypass of abasic sites. These results suggest that in human cells bypass of abasic sites does not require the bypass-specific DNA polymerase eta, but it does require at least one of the replicative DNA polymerases, alpha, delta, or epsilon. The quantitative TLR assay is expected to be useful in the molecular analysis of lesion bypass in a large variety of cultured mammalian cells.

Topics: Adenocarcinoma; Aphidicolin; Base Sequence; Deoxyadenine Nucleotides; DNA Damage; DNA Repair; DNA Replication; DNA-Directed DNA Polymerase; Humans; Lung Neoplasms; Nucleic Acid Synthesis Inhibitors; Plasmids; Transformation, Genetic; Tumor Cells, Cultured

The DNA of bacteriophage Cp-1 replicates at optimal conditions when Cp-1-infected Streptococcus pneumoniae was incubated at 30 degrees C. The in vitro formation of the initiation complex between the terminal protein and 5'-dAMP was only partially inhibited at 37 degrees C whereas an almost complete inhibition of the DNA replication was found at this temperature in vivo. Aphidicolin inhibited the multiplication of phage Cp-1 but not that of Dp-4. This drug did not affect the in vitro formation of the initiation complex but seems to affect extensive Cp-1 DNA replication in vivo.

Topics: Aphidicolin; Bacteriophages; Deoxyadenine Nucleotides; Diterpenes; DNA Replication; DNA-Binding Proteins; DNA, Viral; Streptococcus pneumoniae; Temperature; Viral Proteins; Virus Replication