Park Junsoo, Seo Taegun, Kim Hakzoo, Choe Joonho
Department of Biological Sciences, Korea Advanced Institute of Science and Technology, Daejon 305-701, South Korea.
Mol Cell Biol. 2005 Sep;25(18):8202-14. doi: 10.1128/MCB.25.18.8202-8214.2005.
Replication protein A (RPA) is a single-stranded-DNA-binding protein composed of three subunits with molecular masses of 70, 32, and 14 kDa. The protein is involved in multiple processes of eukaryotic DNA metabolism, including DNA replication, repair, and recombination. In Xenopus, Xenopus RPA-interacting protein alpha has been identified as a carrier molecule of RPA into the nucleus. In this study, human RPA-interacting protein alpha (hRIPalpha) and five novel splice isoforms (named hRIPalpha, hRIPbeta, hRIPgamma, hRIPdelta1, hRIPdelta2, and hRIPdelta3 according to the lengths of their encoding peptides) were cloned. Among hRIP isoforms, hRIPalpha and hRIPbeta were found to be the major splice isoforms and to show different subcellular localizations. While hRIPalpha localized to the cytoplasm, hRIPbeta was found in the PML nuclear body. Modification of hRIPbeta by sumoylation was found to be required for localization to the PML nuclear body. The results of the present work demonstrate that hRIPbeta transports RPA into the PML nuclear body and releases RPA upon UV irradiation. hRIPbeta thus plays an important role in RPA deposition in PML nuclear bodies and thereby supplements RPA for DNA metabolism.
复制蛋白A（RPA）是一种单链DNA结合蛋白，由分子量分别为70、32和14 kDa的三个亚基组成。该蛋白参与真核生物DNA代谢的多个过程，包括DNA复制、修复和重组。在非洲爪蟾中，非洲爪蟾RPA相互作用蛋白α已被鉴定为RPA进入细胞核的载体分子。在本研究中，克隆了人RPA相互作用蛋白α（hRIPα）和五种新的剪接异构体（根据其编码肽的长度分别命名为hRIPα、hRIPβ、hRIPγ、hRIPδ1、hRIPδ2和hRIPδ3）。在hRIP异构体中，hRIPα和hRIPβ被发现是主要的剪接异构体，并表现出不同的亚细胞定位。hRIPα定位于细胞质，而hRIPβ存在于PML核体中。发现hRIPβ的SUMO化修饰是其定位于PML核体所必需的。本研究结果表明，hRIPβ将RPA转运到PML核体中，并在紫外线照射时释放RPA。因此，hRIPβ在RPA在PML核体中的沉积中起重要作用，从而为DNA代谢补充RPA。
