The Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, 986805 Nebraska Medical Center, Omaha, Nebraska 68198-6805, USA.
Biochemistry. 2009 Dec 15;48(49):11817-24. doi: 10.1021/bi9015346.
Human DNA polymerase N (PolN) is an A-family nuclear DNA polymerase whose function is unknown. This study examines the possible role of PolN in DNA repair in human cells treated with PolN-targeted siRNA. HeLa cells with siRNA-mediated knockdown of PolN were more sensitive than control cells to DNA cross-linking agent mitomycin C (MMC) but were not hypersensitive to UV irradiation. The MMC hypersensitivity of PolN knockdown cells was rescued by the overexpression of DNA polymerase-proficient PolN but not by DNA polymerase-deficient PolN. Furthermore, in vitro experiments showed that purified PolN conducts low-efficiency nonmutagenic bypass of a psoralen DNA interstrand cross-link (ICL), whose structure resembles an intermediate in the proposed pathway of ICL repair. These results suggest that PolN might play a role in translesion DNA synthesis during ICL repair in human cells.
人源 DNA 聚合酶 N（PolN）是 A 家族核 DNA 聚合酶，其功能未知。本研究通过 PolN 靶向 siRNA 处理，探讨了 PolN 在人细胞 DNA 修复中的潜在作用。用 siRNA 介导敲低 PolN 的 HeLa 细胞对 DNA 交联剂丝裂霉素 C（MMC）比对照细胞更敏感，但对紫外线照射不敏感。PolN 敲低细胞对 MMC 的敏感性可以通过表达有功能的 PolN 得到挽救，但不能通过表达无功能的 PolN 挽救。此外，体外实验表明，纯化的 PolN 可以低效、非突变地绕过补骨脂素 DNA 链间交联（ICL），其结构类似于所提出的 ICL 修复途径中的中间产物。这些结果表明，PolN 可能在人细胞 ICL 修复过程中的跨损伤 DNA 合成中发挥作用。
