Yamamoto Taichi, Mori Yoko, Ishibashi Toyotaka, Uchiyama Yukinobu, Sakaguchi Norihiro, Furukawa Tomoyuki, Hashimoto Junji, Kimura Seisuke, Sakaguchi Kengo
Department of Applied Biological Science, Faculty of Science and Technology, Science University of Tokyo, 2641 Yamazaki, Noda-shi, 278-8510 Chiba-ken, Japan.
Biochem Biophys Res Commun. 2004 Feb 6;314(2):434-9. doi: 10.1016/j.bbrc.2003.12.144.
We report here the existence of interactions between a ubiquitin-conjugating enzyme, Rad6, from rice, Oryza sativa L. cv. Nipponbare (OsRad6), and Sgt1 (OsSgt1), a novel subunit of the SCF ubiquitin ligase complex. Rad6 is not only related to post-replicational repair but also to the proteasome system, while Sgt1 has a function in kinetochore assembly. The relationship between the two is unexpected, but of great interest. The open reading frames of OsRad6 and OsSgt1 encode predicted products of 152 and 367 amino acid residues, respectively, with molecular weights of 17.3 and 40.9kDa. Two-hybrid and pull-down analyses indicated that OsRad6 binds to OsSgt1, and transcripts of both OsRad6 and OsSgt1 were found to be strongly expressed only in the proliferating tissues such as the shoot apical meristem, suggesting that their expression is cell cycle-dependent. The amount of the Rad6 mRNA in cultured cells increased rapidly after division was halted, and mRNA levels of Rad6 and Sgt1 were induced by UV- and DNA-damaging agents such as MMS or H(2)O(2). The Rad6 pathway for repair or the proteasome system may thus require Sgt1 as ubiquitin-conjugating enzyme.
我们在此报道了来自水稻（Oryza sativa L. cv. Nipponbare）的泛素结合酶Rad6（OsRad6）与SCF泛素连接酶复合体的一个新亚基Sgt1（OsSgt1）之间存在相互作用。Rad6不仅与复制后修复有关，还与蛋白酶体系统有关，而Sgt1在动粒组装中发挥作用。二者之间的关系出人意料，但却非常有趣。OsRad6和OsSgt1的开放阅读框分别编码预测的含有152和367个氨基酸残基的产物，分子量分别为17.3 kDa和40.9 kDa。双杂交和下拉分析表明OsRad6与OsSgt1结合，并且发现OsRad6和OsSgt1的转录本仅在增殖组织如茎尖分生组织中强烈表达，这表明它们的表达是细胞周期依赖性的。在培养细胞中，分裂停止后Rad6 mRNA的量迅速增加，并且Rad6和Sgt1的mRNA水平受到紫外线和DNA损伤剂如MMS或H₂O₂的诱导。因此，用于修复的Rad6途径或蛋白酶体系统可能需要Sgt1作为泛素结合酶。
