Furukawa Tomoyuki, Ishibashi Toyotaka, Kimura Seisuke, Tanaka Hiroshi, Hashimoto Junji, Sakaguchi Kengo
National Institute of Agrobiological Sciences, 2-1-2 Tsukuba-shi, Ibaraki-ken 305-8602, Japan.
Plant Mol Biol. 2003 Sep;53(1-2):15-25. doi: 10.1023/B:PLAN.0000009258.04711.62.
Replication factor C (RFC), which is composed of five subunits, is an important factor involved in DNA replication and repair mechanisms. Following previous studies on the RFC3 homologue from rice (Oryza sativa L. cv. Nipponbare) (OsRFC3), we succeeded in isolating and characterizing one large and three small subunits of RFC homologues from the same rice species and termed them OsRFC1, OsRFC2, OsRFC4 and OsRFC5. The plant was found to have all RFC subunits known in yeasts, human and other eukaryotes. The open reading frames of OsRFCs encoded a predicted product of 1021 amino acid residues with a molecular mass of 110.8 kDa for OsRFC1, 339 amino acid residues with a molecular mass of 37.4 kDa for OsRFC2, 335 amino acid residues with a molecular mass of 36.8 kDa for OsRFC4, and 354 amino acid residues with a molecular mass of 40.5 kDa for OsRFC5. All the OsRFC subunits have highly conserved amino acid motifs among RFC proteins, RFC box, and an unrooted phylogenetic tree shows each OsRFC subunit belongs to each RFC subunit group. These subunits showed differences in their expression patterns among tissues. The transcripts of OsRFCs were expressed strongly in the proliferating tissue, the shoot apical meristem (SAM), and very weakly in the mature leaves which have no proliferating tissues. However, in young leaves and flag leaves, tissue-specific expression of OsRFC3 and OsRFC4 was shown. On the other hand, cell cycle arrest by cell cycle inhibitors resulted in significant differences in OsRFC expression patterns. These results suggest the functional differences of each OsRFC subunit in tissues and the plant cell cycle. The roles of these molecules in plant DNA replication and DNA repair are discussed.
复制因子C（RFC）由五个亚基组成，是参与DNA复制和修复机制的重要因子。在之前对水稻（Oryza sativa L. cv. Nipponbare）的RFC3同源物（OsRFC3）进行研究之后，我们成功地从同一水稻品种中分离并鉴定了RFC同源物的一个大亚基和三个小亚基，并将它们命名为OsRFC1、OsRFC2、OsRFC4和OsRFC5。研究发现该植物具有酵母、人类和其他真核生物中已知的所有RFC亚基。OsRFCs的开放阅读框编码的预测产物中，OsRFC1为1021个氨基酸残基，分子量为110.8 kDa；OsRFC2为339个氨基酸残基，分子量为37.4 kDa；OsRFC4为335个氨基酸残基，分子量为36.8 kDa；OsRFC5为354个氨基酸残基，分子量为40.5 kDa。所有OsRFC亚基在RFC蛋白中都有高度保守的氨基酸基序、RFC框，并且无根系统发育树表明每个OsRFC亚基都属于每个RFC亚基组。这些亚基在不同组织中的表达模式存在差异。OsRFCs的转录本在增殖组织、茎尖分生组织（SAM）中强烈表达，而在没有增殖组织的成熟叶片中表达非常微弱。然而，在幼叶和旗叶中，显示出OsRFC3和OsRFC4的组织特异性表达。另一方面，细胞周期抑制剂导致的细胞周期停滞使得OsRFC的表达模式出现显著差异。这些结果表明每个OsRFC亚基在组织和植物细胞周期中的功能差异。本文还讨论了这些分子在植物DNA复制和DNA修复中的作用。
