Department of Surgical Oncology, Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310009, China.
Biochem Biophys Res Commun. 2011 Jun 24;410(1):102-7. doi: 10.1016/j.bbrc.2011.05.114. Epub 2011 May 25.
Ribonucleotide reductase (RR) is a rate-limiting enzyme that catalyzes de novo conversion of ribonucleotide 5'-diphosphates to the corresponding 2'-deoxynucleotide, essential for DNA synthesis and replication. The mutations or knockout of RR small subunit, p53R2, results in the depletion of mitochondrial DNA (mtDNA) in human, implying that p53R2 might play a critical role for maintaining mitochondrial homeostasis. In this study, siRNA against p53R2 knockdown approach is utilized to examine the impact of p53R2 depletion on mitochondria and to derive underlying mechanism in KB and PC-3 cancer cells. Our results reveal that the p53R2 expression not only positively correlates with mtDNA content, but also partakes in the proper mitochondria function, such as ATP synthesis, cytochrome c oxidase activity and membrane potential maintenance. Furthermore, overexpression of p53R2 reduces intracellular ROS and protects the mitochondrial membrane potential against oxidative stress. Unexpectedly, knockdown of p53R2 has a modest, if any, effect on mitochondrial and total cellular dNTP pools. Taken together, our study provides functional evidence that mitochondria is one of p53R2-targeted organelles and suggests an unexpected function of p53R2, which is beyond known RR function on dNTP synthesis, in mitochondrial homeostatic control.
核糖核苷酸还原酶（RR）是一种限速酶，可催化核苷酸 5'-二磷酸转化为相应的 2'-脱氧核苷酸，这对 DNA 的合成和复制至关重要。RR 小亚基 p53R2 的突变或敲除会导致人类线粒体 DNA（mtDNA）耗竭，这表明 p53R2 可能在维持线粒体稳态方面发挥关键作用。在这项研究中，利用 p53R2 的 siRNA 敲低方法来研究 p53R2 耗竭对线粒体的影响，并探讨其在 KB 和 PC-3 癌细胞中的潜在机制。我们的结果表明，p53R2 的表达不仅与 mtDNA 含量呈正相关，而且还参与适当的线粒体功能，如 ATP 合成、细胞色素 c 氧化酶活性和膜电位维持。此外，p53R2 的过表达可减少细胞内 ROS 并保护线粒体膜电位免受氧化应激的影响。出乎意料的是，p53R2 的敲低对线粒体和总细胞 dNTP 池几乎没有影响。总之，我们的研究提供了功能证据，表明线粒体是 p53R2 靶向的细胞器之一，并提示了 p53R2 的一个意外功能，即在 dNTP 合成之外，参与线粒体稳态的控制。
