Regulation of the salvage pathway of deoxynucleotides synthesis in apoptosis induced by growth factor deprivation.
Here we describe changes in dNTP metabolism that precede DNA fragmentation in a model of apoptosis driven by deprivation of the cytokine interleukin 3 (IL-3). In haemopoietic BAF3 cells, IL-3 withdrawal leads to a rapid decrease in the size of dATP, dTTP and dGTP pools without affecting dCTP levels. This imbalance in dNTP pools precedes DNA fragmentation and is accompanied by down-regulation of enzymes controlling the de novo and salvage pathways of dNTP synthesis, ribonucleotide reductase and thymidine kinase (TK) respectively. Readdition of IL-3 results in a rapid, protein synthesis-independent restoration of normal dNTP pools, enhanced TK activity and increased precursor incorporation through the salvage pathway. Up-regulation of TK activity after IL-3 readdition is prevented by the protein kinase C (PKC) inhibitor staurosporin, but not by tyrosine kinase inhibitors. Furthermore activation of PKC by phorbol esters mimics the stimulatory effect of IL-3 on TK activity, suggesting that PKC might be involved in regulating this effect. These results indicate that regulation by IL-3 of the salvage pathway of dNTP synthesis plays a role in the maintenance of cellular dNTP pool balance and suggests that alterations in dNTP metabolism after IL-3 deprivation could be a relevant event in the commitment of haemopoietic cells to apoptosis.
Oliver
F J
FJ
Instituto de Parasitología y Biomedicina, C.S.I.C., Granada, Spain.
Collins
M K
MK
López-Rivas
A
A
D000818:Animals; D017209:Apoptosis; D002460:Cell Line; D004247:DNA / Q000378:metabolism; D003854:Deoxyribonucleotides / Q000096:biosynthesis / Q000378:metabolism*; D004587:Electrophoresis, Agar Gel; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007377:Interleukin-3 / Q000502:physiology*; D008214:Lymphocytes / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D047428:Protein Kinase Inhibitors; D012264:Ribonucleotide Reductases / Q000378:metabolism; D013937:Thymidine Kinase / Q000378:metabolism; D014529:Uridine / Q000378:metabolism
D003854:Deoxyribonucleotides; D004791:Enzyme Inhibitors; D007377:Interleukin-3; D047428:Protein Kinase Inhibitors; D015240:Phorbol 12,13-Dibutyrate; D004247:DNA; D012264:Ribonucleotide Reductases; D013937:Thymidine Kinase; D014529:Uridine