Specialized DNA polymerases (DNA pols) are required for lesion bypass in human cells. Auxiliary factors have an important, but so far poorly understood, role. Here we analyse the effects of human proliferating cell nuclear antigen (PCNA) and replication protein A (RP-A) on six different human DNA pols--belonging to the B, Y and X classes--during in vitro bypass of different lesions. The mutagenic lesion 8-oxo-guanine (8-oxo-G) has high miscoding potential. A major and specific effect was found for 8-oxo-G bypass with DNA pols lambda and eta. PCNA and RP-A allowed correct incorporation of dCTP opposite a 8-oxo-G template 1,200-fold more efficiently than the incorrect dATP by DNA pol lambda, and 68-fold by DNA pol eta, respectively. Experiments with DNA-pol-lambda-null cell extracts suggested an important role for DNA pol lambda. On the other hand, DNA pol iota, together with DNA pols alpha, delta and beta, showed a much lower correct bypass efficiency. Our findings show the existence of an accurate mechanism to reduce the deleterious consequences of oxidative damage and, in addition, point to an important role for PCNA and RP-A in determining a functional hierarchy among different DNA pols in lesion bypass.

Molecular modeling studies and an updated highly predictive 3-D QSAR model led to the discovery of exceptionally potent indolyl aryl sulfones (IASs) characterized by the presence of either a pyrrolidyn-2-one nucleus at the indole-2-carboxamide or some substituents at the indole-2-carbohydrazide. Compounds 7 and 9 were found active in the sub-nanomolar range of concentration in both MT-4 and C8166 cell-based anti-HIV assays. These compounds, and in particular compound 9, also showed excellent inhibitory activity against both HIV-112 and HIV-AB1 primary isolates in lymphocytes and against HIV WT in macrophages.

Significance Macromolecules (DNA, proteins, and lipids) in all cells are constantly damaged by reactive oxygen species (ROS). In particular, ROS cause 1,000–7,000 DNA damages per day. Due to its lowest redox potential, the base guanine is mostly affected, resulting in the formation of 8-oxo-7,8-dihydroguanine. This modified base instructs incorporation of adenosine, instead of cytidine, by replicative DNA polymerases, potentially leading to GC→TA transversion mutations. DNA polymerase λ is the most efficient enzyme in performing accurate translesion synthesis over 8-oxo-7,8-dihydroguanine, since it preferentially incorporates the correct cytidine. In this paper we found that the protein called “DNA polymerase δ interacting protein 2” supports DNA polymerase λ in its important task and can protect cells from ROS DNA damage.