Conservative regulation of DNA replication and transcription in mammalian cells

C-MYC与多种蛋白质形成复合物，发挥多种作用。1）MSSP MSSP是c-myc基因起始/增强子上的DNA结合蛋白。MSSP作为DNA复制和转录因子发挥作用。2）AMY-1利用双杂交系统克隆了编码AMY-1的新cDNA。AMY-1定位于细胞核内，通过C端与C-MYC的N端结合。3）Pim-1 Pim-1能转化c-myc细胞，并能促进c-myc的转化。我们发现Pim-1与C-MYC直接相关，Pim-1通过其过表达诱导细胞凋亡。4）DNA聚合酶a和cdk 2与C-MYC和MSSP的结合位点均位于DNA聚合酶a催化亚基的N端，与G1/S检查点蛋白cdk 2的结合位点也位于C-MYC和MSSP的N端。MSSP刺激聚合酶活性。这些结果表明MSSP/C-MYC在G1/S期起着关键作用，尤其是在DNA复制的启动过程中。

C-MYC is making complex with a variety of proteins to play numerous roles. We have identified and cloned cDNAs encoding MYC-binding proteins.1) MSSP MSSP was found as an DNA binding protein on origin/enhancer in c-myc gene. MSSP plays a role as DNA replication and transcription factor. MSSP binds to N-terminal portion of C-MYC via its C-terminus portion.2) AMY-1 Using two hybrid system we cloned a novel cDNA encoding AMY-1. AMY-1 was located in the nucleus, and bound to N-terminal region of C-MYC via its C-terminus. AMY-1 acted as a transcription factor and stimulated transcriptional activity of C-MYC.AMY-1 also stimulated C-MYC's transforming activity dramatically.3) Pim-1 Pim-1 was known to transform cells with c-myc. Here we found that Pim-1 was directly associated with C-MYC.Pim-1 induced apoptosis by its overexpression. Signal transduction from Pim-1 to C-MYC may contribute apoptosis pathway.4) DNA polymerase a and cdk2 C-MYC and MSSP were also bound to N-terminal portion of catalytic subunit of DNA polymerase a and cdk2, a protein for G1/S checkpoint protein. MSSP stimulated polymerase activity. These results indicated that MSSP/C-MYC play a key role G1/S,especially the initiation of DNA replication.