Retinoblastoma tumor suppressor targets dNTP metabolism to regulate DNA replication
Retinoblastoma tumor suppressor targets dNTP metabolism to regulate DNA replication
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DOI：
10.1074/jbc.m205911200
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发表时间：
2002-11-15
影响因子：
4.8
通讯作者：
Knudsen, ES
中科院分区：
文献类型：
--
作者：
Angus, SP;Wheeler, LJ;Knudsen, ES
视网膜母细胞瘤肿瘤抑制因子1113是细胞周期的负调控因子，在大多数人类肿瘤中处于失活状态。Rb对细胞周期的抑制作用归因于CDK2活性的减弱。尽管异位周期素部分克服了RB介导的S期在复制分叉处的停滞，但DNA复制仍然受到抑制，细胞无法进展到G(2)期。这些数据表明，Rb在S阶段调节了一个额外的执行点。我们观察到，结构性活性1113减弱了特定dNTP合成酶的表达：二氢叶酸还原酶、核糖核苷酸还原酶(RNR)亚基R1/R2和胸苷合成酶(TS)。P16INK4a对内源Rb及相关蛋白的激活对酶的表达也有类似的影响。相反，靶向阻断Rb导致代谢蛋白水平(二氢叶酸还原酶，TS，RNR-R2)增加，并对TS或RNR抑制剂减少可用dNTPs的作用产生抵抗。对RB介导的细胞周期停滞期间dNTP池的分析显示，在TS和RNR蛋白丢失的同时，dNTP池显著枯竭。重要的是，活性Rb对细胞周期位置和有效dNTPs的影响与特定抗代谢药物的效果相当。综上所述，这些结果表明，RB介导的转录抑制减弱了可用于控制S阶段进展的dNTP池。因此，Rb同时采用规范的细胞周期蛋白依赖的激酶/细胞周期蛋白调节和代谢调节作为限制增殖的手段，强调了其在肿瘤抑制中的效力。
The retinoblastoma tumor suppressor, 1113, is a negative regulator of the cell cycle that is inactivated in the majority of human tumors. Cell cycle inhibition elicited by RB has been attributed to the attenuation of CDK2 activity. Although ectopic cyclins partially overcome RB-mediated S-phase arrest at the replication fork, DNA replication remains inhibited and cells fail to progress to G(2) phase. These data suggest that RB regulates an additional execution point in S phase. We observed that constitutively active 1113 attenuates the expression of specific dNTP synthetic enzymes: dihydrofolate reductase, ribonucleotide reductase (RNR) subunits R1/R2, and thymidylate synthase (TS). Activation of endogenous RB and related proteins by p16ink4a yielded similar effects on enzyme expression. Conversely, targeted disruption of RB resulted in increased metabolic protein levels (dihydrofolate reductase, TS, RNR-R2) and conferred resistance to the effect of TS or RNR inhibitors that diminish available dNTPs. Analysis of dNTP pools during RB-mediated cell cycle arrest revealed significant depletion, concurrent with the loss of TS and RNR protein. Importantly, the effect of active RB on cell cycle position and available dNTPs was comparable to that observed with specific antimetabolites. Together, these results show that RB-mediated transcriptional repression attenuates available dNTP pools to control S-phase progression. Thus, RB employs both canonical cyclin-dependent kinase/cyclin regulation and metabolic regulation as a means to limit proliferation, underscoring its potency in tumor suppression.