RT Journal Article
SR Electronic
T1 Inhibition of the Synthesis of Thymine Nucleotides by Azaserine
JF Molecular Pharmacology
JO Mol Pharmacol
FD American Society for Pharmacology and Experimental Therapeutics
SP 71
OP 80
VO 3
IS 1
A1 ALAN C. SARTORELLI
A1 BARBARA A. BOOTH
YR 1967
UL http://molpharm.aspetjournals.org/content/3/1/71.abstract
AB The synthesis of purine nucleotides de novo in sarcoma 180 ascites cells propagated in mice was essentially completely inhibited for a prolonged period of time by azaserine (O-diazoacetyl-L-serine); this metabolic blockade resulted in a 60% decrease in the amount of adenine nucleotides in time cells. Concurrently, in the antibiotic-treated cells, the incorporation of thymidine-3H, formate-14C and deoxycytidine-3H into the thymine of DNA was markedly depressed, while the utilization of orotic acid-14C and leucine-14C for the formation of RNA and proteins, respectively, was unaffected. Azaserine did not decrease the rate of incorporation of adenine-14C into the purine nucleotides of DNA and RNA, suggesting that the polymerization processes per se were not altered by the drug. The inhibition of the incorporation of labeled precursors into the thymine of DNA in azaserine-treated cells was accounted for by a pronounced depression in the levels of thymidine kinase (ATP:thymidine 5'-phosphotransferase, EC 2.7.1.21) and thymidine monophosphate kinase (ATP:thymidine monophosphate phosphotransferase, EC 2.7.4.9). The availability to the cells of a supply of preformed adenine restored both the azaserinedepleted pool of adenine nucleotides and the activities of the thymine nucleotide-synthesizing enzymes; in this capacity, hypoxanthine was only slightly effective, while guanosine and azapurines were ineffective in reversing the azaserine-induced metabolic lesions. The results suggested a possible role for adenine nucleotides in regulating the activities of thymidine kinase and thymidine monophosphate kinase in intact cells. ACKNOWLEDGMENTS This investigation was supported by USPHS Research Giant CA-02817 from the National Cancer Institute. The authors wish to thank Mrs. Theresa Cheng, Miss Florence C. Dunmore, Miss Sheila J. Feld, and Miss Andrea F. Gorske for excellent technical assistance.