METABOLIC CONSEQUENCES OF ADENINE-PHOSPHORIBOSYL TRANSFERASE DEFICIENCY IN V79 HAMSTER FIBROBLASTS

Two APRT- clones (V79-E3 and V79-E1A) were isolated from V79 hamster fibroblasts treated with ethyl methanesulfonate. Selection involved sequential exposure of the mutagenized cells to the adenine analogues 8-azaadenine and 2,6-diaminopurine. To examine the influence of APRT deficiency on cell metabolism we determined the size and turnover of adenine ribonucleotide pools, the deoxyribonucleoside triphosphate pools, the rate of DNA synthesis, and the length of the cell cycle. Clone V79-E3 was hemizygous for aprt and carried a new chromosome, 3p-. Clone V79-E1A was quasitetraploid with a cell volume more than twice that of the WT cells. When the difference in size was taken into account, both clones behaved similarly. While WT V79 cells released no adenine into the medium, they excreted adenine at a rate of 6 pmol/min. This did not affect the size of the ATP pool. The main change in the deoxynucleotide pools was a marked decrease of the concentration of dCTP. The rate of DNA synthesis was the same in WT cells and in the diploid V79-E3 clone. APRT is known to recycle adenine produced during polyamine synthesis, but the enzyme apparently contributes little to the maintenance of adenine ribonucleotide pools of V79 fibroblasts. © 1992.