A role for DNA polymerase beta in mutagenic UV lesion bypass.
We report here that DNA polymerase beta (pol beta), the base excision repair polymerase, is highly expressed in human melanoma tissues, known to be associated with UV radiation exposure. To investigate the potential role of pol beta in UV-induced genetic instability, we analyzed the cellular and molecular effects of excess pol beta. We firstly demonstrated that mammalian cells overexpressing pol beta are resistant and hypermutagenic after UV irradiation and that replicative extracts from these cells are able to catalyze complete translesion replication of a thymine-thymine cyclobutane pyrimidine dimer (CPD). By using in vitro primer extension reactions with purified pol beta, we showed that CPD as well as, to a lesser extent, the thymine-thymine pyrimidine-pyrimidone (6-4) photoproduct, were bypassed. pol beta mostly incorporates the correct dATP opposite the 3'-terminus of both CPD and the (6-4) photoproduct but can also misinsert dCTP at a frequency of 32 and 26%, respectively. In the case of CPD, efficient and error-prone extension of the correct dATP was found. These data support a biological role of pol beta in UV lesion bypass and suggest that deregulated pol beta may enhance UV-induced genetic instability.
Servant
Laurence
L
Group "Genetic instability and cancer" at the Institut de Pharmacologie et Biologie Structurale, UMR CNRS 5089, 31077 Toulouse cédex 4, France.
Cazaux
Christophe
C
Bieth
Anne
A
Iwai
Shigenori
S
Hanaoka
Fumio
F
Hoffmann
Jean-Sébastien
JS
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D015153:Blotting, Western; D016466:CHO Cells; D002384:Catalysis; D006224:Cricetinae; D004247:DNA / Q000378:metabolism / Q000528:radiation effects*; D018736:DNA Adducts; D004249:DNA Damage; D019951:DNA Polymerase beta / Q000378:metabolism / Q000502:physiology*; D019281:Dimerization; D004926:Escherichia coli / Q000378:metabolism; D007700:Kinetics; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009154:Mutation; D010641:Phenotype; D051381:Rats; D013539:Simian virus 40 / Q000378:metabolism; D014466:Ultraviolet Rays; D015854:Up-Regulation
D018736:DNA Adducts; D000255:Adenosine Triphosphate; D004247:DNA; D019951:DNA Polymerase beta