Cdt1 and geminin are down-regulated upon cell cycle exit and are over-expressed in cancer-derived cell lines
Cdt1 and geminin are down-regulated upon cell cycle exit and are over-expressed in cancer-derived cell lines
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DOI：
10.1111/j.1432-1033.2004.04271.x
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发表时间：
2004-08-01
期刊：
影响因子：
--
通讯作者：
Taraviras, S
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文献类型：
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作者：
Xouri, G;Lygerou, Z;Taraviras, S
在有丝分裂完成后许可复制起点确保了循环细胞中基因组的稳定性。cdt 1是最近发现的一个重要的许可因子，它被双生蛋白抑制。Cdt 1的过度表达被证明易使细胞发生恶性转化。我们在这里表明，Cdt 1是下调在蛋白质和RNA水平时，原代人成纤维细胞退出细胞周期进入G 0，其表达诱导细胞重新进入细胞周期，S期开始之前。Cdt 1的抑制剂geminin在蛋白质和RNA水平上在细胞周期退出时类似地下调，并且在血清再添加后，geminin蛋白积累比Cdt 1延迟3-6小时。同样，小鼠NIH 3 T3细胞下调Cdt 1和geminin mRNA和蛋白质时，血清饥饿。我们的数据表明，Cdt 1和双生蛋白的转录控制从静止到增殖的过渡。原位杂交和免疫组织化学定位Cdt 1以及双生蛋白的发育小鼠肠上皮细胞的增殖室。Cdt 1和双生蛋白水平在原代细胞与癌症衍生的人细胞系中进行比较。我们发现Cdt 1在蛋白质和RNA水平上都在癌细胞系中持续过表达，并且Cdt 1蛋白在单个癌细胞中积累到更高的水平。Geminin在大多数测试的癌细胞系中同样过表达。Cdt 1和geminin的相对比率在细胞系之间显著不同。我们的数据表明Cdt 1和geminin在细胞周期退出时受到调节，并表明控制Cdt 1和geminin水平的机制可能在癌细胞中发生改变。
Licensing origins for replication upon completion of mitosis ensures genomic stability in cycling cells. Cdt1 was recently discovered as an essential licensing factor, which is inhibited by geminin. Over-expression of Cdt1 was shown to predispose cells for malignant transformation. We show here that Cdt1 is down-regulated at both the protein and RNA level when primary human fibroblasts exit the cell cycle into G0, and its expression is induced as cells re-enter the cell cycle, prior to S phase onset. Cdt1's inhibitor, geminin, is similarly down-regulated upon cell cycle exit at both the protein and RNA level, and geminin protein accumulates with a 3-6 h delay over Cdt1, following serum re-addition. Similarly, mouse NIH3T3 cells down-regulate Cdt1 and geminin mRNA and protein when serum starved. Our data suggest a transcriptional control over Cdt1 and geminin at the transition from quiescence to proliferation. In situ hybridization and immunohistochemistry localize Cdt1 as well as geminin to the proliferative compartment of the developing mouse gut epithelium. Cdt1 and geminin levels were compared in primary cells vs. cancer-derived human cell lines. We show that Cdt1 is consistently over-expressed in cancer cell lines at both the protein and RNA level, and that the Cdt1 protein accumulates to higher levels in individual cancer cells. Geminin is similarly over-expressed in the majority of cancer cell lines tested. The relative ratios of Cdt1 and geminin differ significantly amongst cell lines. Our data establish that Cdt1 and geminin are regulated at cell cycle exit, and suggest that the mechanisms controlling Cdt1 and geminin levels may be altered in cancer cells.