Giuseppe Villani

Replication protein A and proliferating cell nuclear antigen coordinate DNA polymerase selection in 8-oxo-guanine repair

The adenine misincorporated by replicative DNA polymerases (pols) opposite 7,8-dihydro-8-oxoguanine (8-oxo-G) is removed by a specific glycosylase, leaving the lesion on the DNA. Subsequent incorporation of C opposite 8-oxo-G on the resulting 1-nt gapped DNA is essential for the removal of the 8-oxo-G to prevent G–C to T–A transversion mutations. By using model DNA templates, purified DNA pols β and λ and knockout cell extracts, we show here that the auxiliary proteins replication protein A and proliferating cell nuclear antigen act as molecular switches to activate the DNA pol λ- dependent highly efficient and faithful repair of A:8-oxo-G mismatches in human cells and to repress DNA pol β activity. By using an immortalized human fibroblast cell line that has the potential to induce cancer in mice, we show that the development of a tumoral phenotype in these cells correlated with a differential expression of DNA pols λ and β.

DNA Polymerases: Discovery, Characterization and Functions in Cellular DNA Transactions

Maintenance of the information embedded in the genomic DNA sequence is essential for life. DNA polymerases play pivotal roles in the complex physiological processes of DNA replication and repair. Besides the tasks in vivo, DNA polymerases are the workhorses in numerous biotechniques such as polymerase chain reaction (PCR), cDNA cloning, genome sequencing, nucleic acids-based diagnostics, as well as techniques to analyze ancient and otherwise damaged DNA. The authors have recently witnessed the discovery of a plethora of novel DNA polymerases with specialized properties whose physiological functions are only just beginning to be understood. This book summarizes the current knowledge of these fascinating enzymes in viruses, bacteria, archaea and eukaryotes. Moreover, some diseases are related to DNA polymerase defects, and chemotherapy through inhibition of DNA polymerases is used to fight HIV, Herpes, as well as Hepatitis B and C infections. This book will appeal to a broad audience including basic scientists, diagnostic laboratories, and clinicians who will gain an invaluable understanding of these fascinating enzymes.

Interaction of cis-diamminedichloroplatinum (II) with single-stranded DNA in the presence or absence of escherichia coli singlestranded binding protein

We have compared the mode of fixation in vitro of the antitumor drug cis-diamminedichloroplatinum (II) (cis-DDP) to single-stranded M13mp10 DNA either in the presence or absence of the Escherichia coli single-stranded binding protein (SSB). Platinum binding sites have been identified by taking advantage of their capacity to inhibit DNA replication of primed M13 DNA catalysed by E. coli DNA polymerase I large fragment. We report here that the presence of SSB increases the number of platinum-DNA lesions and alters their distribution. We also present evidence that SSB allows cis-DDP to bind to DNA sequences otherwise less accessible.