1. Institute of Molecular Genetics IGM-CNR, via Abbiategrasso 207, I-27100 Pavia, Italy
2. Institute de Pharmacologie et de Biologie Structurale, IPBS-CNRS, Centre National de la Recherche Scientifique, Route de Narbonne 205, 31077 Toulouse, France
3. Institute National Français de Recherche Médicale, Université Paris Descartes, Faculté de Médecine René Descartes, Site Necker-Enfants Malades, 156 rue de Vaugirard 75730 Paris, Cedex 15, France
4. Institute for Veterinary Biochemistry and Molecular Biology, University of Zürich-Irchel, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland

Correspondence to: Giovanni Maga^1,4 Correspondence and requests for materials should be addressed to G.M. (Email: maga@igm.cnr.it).

Abstract

Specialized DNA polymerases (DNA pols) are required for lesion bypass in human cells¹. 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^{2, 3, 4}. A major and specific effect was found for 8-oxo-G bypass with DNA pols  and . 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 , and 68-fold by DNA pol , respectively. Experiments with DNA-pol--null cell extracts suggested an important role for DNA pol . On the other hand, DNA pol , together with DNA pols , and , 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.

MORE ARTICLES LIKE THIS

These links to content published by NPG are automatically generated.