Vol. 173, No. 2, 1990 December 14, 1990 BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS Pages 704-710 MUTAGENIC PROPERTIES OF A UNIQUE ABASIC SITE IN MAMMALIAN CELLS A. GENTIL, G. RENAULT, C. MADZAK, A. MARGOT, J. B. CABRAL-NETO, J.J. VASSEUR*, B. RAYNER*, J.L. IMBACH* and A. SARASIN Laboratory of Molecular Genetics, Institut de Recherches Scientifiques sur le Cancer, B.P. n° 8 - 94801-VILLEJUIF, France *Laboratoire de Chimie Bio-organique, UA 488, C.N.R.S., Universit6 des Sciences et Techniques du Languedoc, Place E. Bataillon, 34060 MONTPELLIER Cedex, France Received October 26, 1990 Summary : The mutagenic properties of a true unique abasic site located opposite a guanine residue were studied. An oligonucleotide containing a chemically-produced abasic site was inserted into a shuttle vector able to replicate both in simian cells and in bacteria. Plasmid DNA was rescued from simian cells and screened in bacteria by differential hybridization with a labelled oligonucleotide probe. Mutations were easily dectected and sequenced. Results showed that opposite a guanine the abasic site was error free repaired or replicated by mammalian cells with an efficiency of 99%. Point mutations occurred at a frequency of approximately 1% in control host cells and at more than 3% in UV-pre-irradiated host cells. Adenine, cytosine or thymine were found to have been inserted opposite the abasic site. No preferential insertion for a particular base was observed in contrast to that reported in bacteria. ~199o Academic Pr .... Inc. Abasic sites are lesions which appear in the genome with a high frequency in both bacteria and mammalian cells by either spontaneous hydrolysis of the N-glycosylic bond or by treatment with physical or chemical agents (for review see Ref 1). Moreover abasic sites are produced at an intermediary step during repair of damaged DNA as a consequence of DNA glycosylase attack of modified bases (2). Abasic sites have been shown to be mutagenic both in prokaryotes and eukaryotes (3-5). In prokaryotes, it has been demonstrated a certain preference for adenine insertion opposite putative apurinic sites (6,7) whereas nothing is known about mutagenic 0006-291X/90 $1.50 Copyright © 1990 by Academic Press, Inc. All rights of reproduction in any form reserved. 704