Frouin Isabelle, Toueille Magali, Ferrari Elena, Shevelev Igor, Hübscher Ulrich
Institute of Veterinary Biochemistry and Molecular Biology, University of Zürich-Irchel Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.
Nucleic Acids Res. 2005 Sep 20;33(16):5354-61. doi: 10.1093/nar/gki845. Print 2005.
DNA polymerase (Pol) lambda is a member of the Pol X family and possesses four different enzymatic activities, being DNA polymerase, terminal transferase, deoxyribose phosphate lyase and polynucleotide synthetase, all localized in its C-terminal region. On the basis of its biochemical properties, Pol lambda has been implicated in various DNA repair pathways, such as abasic site translesion DNA synthesis, base excision repair and non-homologous end joining of double strand breaks. However, its role in vivo has not yet been elucidated. In addition, Pol lambda has been shown to interact with the replication clamp proliferating cell nuclear antigen (PCNA) in vitro and in vivo. In this work, we searched by affinity chromatography for novel partners and we identified the cyclin-dependent kinase Cdk2 as novel partner of Pol lambda. Pol lambda is phosphorylated in vitro by several Cdk/cyclin complexes, including Cdk2/cyclin A, in its proline-serine-rich domain. While the polymerase activity of Pol lambda was not affected by Cdk2/cyclin A phosphorylation, phosphorylation of Pol lambda was decreased by its interaction with PCNA. Finally, Pol lambda is also phosphorylated in vivo in human cells and this phosphorylation is modulated during the cell cycle.
DNA聚合酶（Pol）λ是Pol X家族的成员，具有四种不同的酶活性，即DNA聚合酶、末端转移酶、脱氧核糖磷酸裂解酶和多核苷酸合成酶，所有这些活性都位于其C末端区域。基于其生化特性，Pol λ参与了多种DNA修复途径，如无碱基位点跨损伤DNA合成、碱基切除修复和双链断裂的非同源末端连接。然而，其在体内的作用尚未阐明。此外，已证明Pol λ在体外和体内均与复制钳增殖细胞核抗原（PCNA）相互作用。在这项工作中，我们通过亲和色谱法寻找新伙伴，并鉴定出细胞周期蛋白依赖性激酶Cdk2是Pol λ的新伙伴。在体外，Pol λ在其富含脯氨酸-丝氨酸的结构域中被几种Cdk/细胞周期蛋白复合物磷酸化，包括Cdk2/细胞周期蛋白A。虽然Pol λ的聚合酶活性不受Cdk2/细胞周期蛋白A磷酸化的影响，但其与PCNA的相互作用会降低Pol λ的磷酸化水平。最后，Pol λ在人类细胞中也会在体内发生磷酸化，并且这种磷酸化在细胞周期中受到调节。
