Control of dTTP pool size by anaphase promoting complex/cyclosome is essential for the maintenance of genetic stability.
Anaphase promoting complex/cyclosome (APC/C)-mediated proteolysis is essential for chromosome segregation, mitotic exit, and G1 entry. Here, we show the importance of APC/C in the control of dTTP pool size in mammalian cells. Two enzymes, thymidine kinase 1 (TK1) and thymidylate kinase (TMPK), involved in dTTP formation are the targets of the APC/C pathway. We demonstrate that TMPK is recognized and degraded by APC/C-Cdc20/Cdh1-mediated pathways from mitosis to the early G1 phase, whereas TK1 is targeted for degradation by APC/C-Cdh1 after mitotic exit. Overexpression of wild-type TK1 and TMPK induces a four- to fivefold increase in the cellular dTTP pool without promoting spontaneous mutations in the hprt (hypoxanthine-guanine phosphoribosyl transferase) gene. In contrast, coexpression of nondegradable TK1 and TMPK expands the dTTP pool size 10-fold accompanied by a drastic dNTP pool imbalance. Most interestingly, disruption of APC/C proteolysis of TK1 and TMPK leads to growth retardation and a striking increase in gene mutation rate. We conclude that down-regulation of dTTP pool size by the APC/C pathway during mitosis and the G1 phase is an essential means to maintain a balanced dNTP pool and to avoid genetic instability.
Ke
Po-Yuan
PY
Graduate Institute of Biochemistry and Molecular Biology, College of Medicine, National Taiwan University, Taipei.
Kuo
Yuan-Yeh
YY
Hu
Chuan-Mei
CM
Chang
Zee-Fen
ZF
D000705:Anaphase / Q000235:genetics*; D064173:Anaphase-Promoting Complex-Cyclosome; D000818:Animals; D064199:Cdc20 Proteins; D018797:Cell Cycle Proteins / Q000502:physiology; D042822:Genomic Instability / Q000235:genetics / Q000502:physiology*; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008938:Mitosis / Q000502:physiology; D041681:NIH 3T3 Cells; D009703:Nucleoside-Phosphate Kinase / Q000378:metabolism; D013937:Thymidine Kinase / Q000378:metabolism; D013942:Thymine Nucleotides / Q000378:metabolism*; D043743:Ubiquitin-Protein Ligase Complexes / Q000235:genetics / Q000502:physiology*
D064199:Cdc20 Proteins; D018797:Cell Cycle Proteins; D013942:Thymine Nucleotides; C577488:CDC20 protein, human; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome; D013937:Thymidine Kinase; C092717:thymidine kinase 1; D009703:Nucleoside-Phosphate Kinase; C020093:dTMP kinase; C024157:thymidine 5'-triphosphate