RT Journal Article SR Electronic T1 Dysregulation of Purine Nucleotide Biosynthesis Pathways Modulates Cisplatin Cytotoxicity in Saccharomyces cerevisiae JF Molecular Pharmacology JO Mol Pharmacol FD American Society for Pharmacology and Experimental Therapeutics SP 1092 OP 1100 DO 10.1124/mol.108.048256 VO 74 IS 4 A1 Kowalski, David A1 Pendyala, Lakshmi A1 Daignan-Fornier, Bertrand A1 Howell, Stephen B. A1 Huang, Ruea-Yea YR 2008 UL http://molpharm.aspetjournals.org/content/74/4/1092.abstract AB We found previously that inactivation of the FCY2 gene, encoding a purine-cytosine permease, or the HPT1 gene, encoding the hypoxanthine guanine phosphoribosyl transferase, enhances cisplatin resistance in yeast cells. Here, we report that in addition to fcy2Δ and hpt1Δ mutants in the salvage pathway of purine nucleotide biosynthesis, mutants in the de novo pathway that disable the feedback inhibition of AMP and GMP biosynthesis also enhanced cisplatin resistance. An activity-enhancing mutant of the ADE4 gene, which constitutively synthesizes AMP and excretes hypoxanthine, and a GMP kinase mutant (guk1), which accumulates GMP and feedback inhibits Hpt1 function, both enhanced resistance to cisplatin. In addition, overexpression of the ADE4 gene in wild-type cells, which increases de novo synthesis of purine nucleotides, also resulted in elevated cisplatin resistance. Cisplatin cytotoxicity in wild-type cells was abolished by low concentration of extracellular purines (adenine, hypoxanthine, and guanine) but not cytosine. Inhibition of cytotoxicity by exogenous adenine was accompanied by a reduction of DNA-bound cisplatin in wild-type cells. As a membrane permease, Fcy2 may mediate limited cisplatin transport because cisplatin accumulation in whole cells was slightly affected in the fcy2Δ mutant. However, the fcy2Δ mutant had a greater effect on the amount of DNA-bound cisplatin, which decreased to 50 to 60% of that in the wild-type cells. Taken together, our results indicate that dysregulation of the purine nucleotide biosynthesis pathways and the addition of exogenous purines can modulate cisplatin cytotoxicity in Saccharomyces cerevisiae. The American Society for Pharmacology and Experimental Therapeutics