MOLECULAR MECHANISMS OF THE CELL CYCLE REGULATION BY REPLICATION/TRANSCRIPTION FACTORS,MSSP

复制/转录因子调控细胞周期的分子机制

基本信息

批准号：
07044213
负责人：
ARIGA Sanae
金额：
$ 3.2万
依托单位：
Hokkaido University
依托单位国家：
日本
项目类别：
Grant-in-Aid for international Scientific Research
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1997
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07044213/
关键词：
REPLICATION TRANSCRIPTION MSSP C-MYC CELL CYCLE YEAST DNA BINDING PROTEINS AMY-1 DNAポリメラーゼ DNAポリメラーゼα 核移行阻止

项目摘要

MSSP,myc single strand binding proteins, have been identified as replication/transcription factors and shown to form specific complex with various proteins including C-MYC and cdc kinase. In addition, MSSP directly bound to DNA polymerase alpha, which is a major enzyme of DNA replication, and stimulated its activity in vitro. Competitive binding to MSSP was observed among C-MYC,cdc kinase and DNA polymerase alpha. MSSP was thus suggested to play an important role in the 'licencing' process at the progression from the G1 phase to the S phase of the cell cycle. The analyzes of the genomic MSSP gene revealed that the expression of MSSP was regulated according to the cell cycle by the sequences upstreem from the promoter and the expression was induced in the early G1 phase and reached a peak from the late G1 to the early S phase as that of C-MYC.Since the introduction of MSSP to cells resulted in activation not only of replication but also of transcription from various promoters, MSSP was suggested to be regulatory factors for both replication and transcription. The results we have obtained, however, indicate that MSSP is directly involved in the regulation of replication initiation and make cells 'licensed' to enter the S phase together with C-MYC,and that the transcription is subsequently activated or repressed. Another C-MYC binding protein, AMY-1 (associated with C-MYC) , has been cloned by the yeast two-hybrid system. AMY-1, as well as MSSP,specifically recognizes the N-terminal region covering the myc boxes. AMY-1 has a transactivation activity and localizes on and along the nuclear membrane on the cytoplasmic side, but translocates into nucleus in the late G1 and the early S phase when the C-MYC expression becomes high. These results hence strongly suggest that the competitive binding to C-MYC between the replication factor MSSP and the transcription factor AMY-1 functions as a switch of the cell 'licencing' to the S phase by C-MYC.

MSSP，MYC单链结合蛋白已被鉴定为复制/转录因子，并显示出与包括C-MYC和CDC激酶在内的各种蛋白质形成特定复合物。此外，MSSP直接与DNA聚合酶α结合，这是DNA复制的主要酶，并在体外刺激其活性。在C-MYC，CDC激酶和DNA聚合酶α中观察到与MSSP的竞争性结合。因此，建议MSSP在从G1阶段到细胞周期的S阶段的“许可”过程中起重要作用。基因组MSSP基因的分析表明，MSSP的表达受启动子的序列上下的细胞周期调节，并且在G1早期诱导了表达，并从G1晚期到早期S相达到峰由于C-Myc.由于将MSSP引入细胞不仅会激活复制，而且还导致了来自各种启动子的转录，因此MSSP被认为是复制和转录的调节因素。但是，我们获得的结果表明，MSSP直接参与了复制起始的调控，并使细胞“许可”与C-MYC一起进入S相，并且随后被激活或抑制了转录。另一个C-Myc结合蛋白AMY-1（与C-MYC相关）已由酵母双杂交系统克隆。 AMY-1以及MSSP专门识别覆盖MYC框的N末端区域。 AMY-1具有反式激活活性，并在细胞质侧的核膜上和沿线定位，但在G1晚期和S早期S阶段转移成核，当C-MYC表达变高。因此，这些结果强烈表明，复制因子MSSP和转录因子AMY-1之间与C-MYC的竞争结合是通过C-MYC将单元“许可”转换为S相的转换。