Department of Pathology, NYU Cancer Institute, New York University School of Medicine, 522 First Avenue, SRB 1107, New York, NY 10016, USA.
Cell. 2012 May 25;149(5):1023-34. doi: 10.1016/j.cell.2012.03.043.
F-box proteins are the substrate binding subunits of SCF (Skp1-Cul1-F-box protein) ubiquitin ligase complexes. Using affinity purifications and mass spectrometry, we identified RRM2 (the ribonucleotide reductase family member 2) as an interactor of the F-box protein cyclin F. Ribonucleotide reductase (RNR) catalyzes the conversion of ribonucleotides to deoxyribonucleotides (dNTPs), which are necessary for both replicative and repair DNA synthesis. We found that, during G2, following CDK-mediated phosphorylation of Thr33, RRM2 is degraded via SCF(cyclin F) to maintain balanced dNTP pools and genome stability. After DNA damage, cyclin F is downregulated in an ATR-dependent manner to allow accumulation of RRM2. Defective elimination of cyclin F delays DNA repair and sensitizes cells to DNA damage, a phenotype that is reverted by expressing a nondegradable RRM2 mutant. In summary, we have identified a biochemical pathway that controls the abundance of dNTPs and ensures efficient DNA repair in response to genotoxic stress.
F-box 蛋白是 SCF（Skp1-Cul1-F-box 蛋白）泛素连接酶复合物的底物结合亚基。通过亲和纯化和质谱分析，我们鉴定出 RRM2（核糖核苷酸还原酶家族成员 2）是 F-box 蛋白 cyclin F 的相互作用蛋白。核糖核苷酸还原酶（RNR）催化核苷酸转化为脱氧核苷酸（dNTPs），这是复制和修复 DNA 合成所必需的。我们发现，在 G2 期，CDK 介导的 Thr33 磷酸化后，RRM2 通过 SCF（cyclin F）降解，以维持平衡的 dNTP 池和基因组稳定性。在 DNA 损伤后，cyclin F 以 ATR 依赖性方式下调，以允许 RRM2 的积累。cyclin F 的消除缺陷会延迟 DNA 修复，并使细胞对 DNA 损伤敏感，这种表型可通过表达不可降解的 RRM2 突变体来逆转。总之，我们已经确定了一个生化途径，该途径控制着 dNTP 的丰度，并确保在应对遗传毒性应激时有效地修复 DNA。
