Characterization of Cdc7 functional domains

细胞分裂过程受到严格调控，并与其遗传物质（DNA）的复制密切协调。这一过程的紊乱可能是致命的或导致遗传不稳定。被称为Cdc 7的蛋白激酶通过连接细胞周期引擎（即，细胞周期蛋白依赖性激酶）和复制机制（即，复制DNA的酶）。为了发挥其功能，Cdc 7必须进入细胞核，然后与染色质结合（即，DNA复制开始的地方。通过突变分析，我们先前发现氨基酸片段203-370包含Cdc 7核输入的信号。我们还发现片段306-326包含Cdc 7核保留的信号，可能是通过结合到新DNA合成开始的染色质。这种核滞留信号显然被Cdc 7蛋白羧基末端的两个小片段所拮抗，我们将其统称为核输出序列。目前，我们还不清楚：（a）细胞核导入和滞留信号是一个整合的信号还是两个独立的信号;（B）细胞核滞留序列的21个氨基酸片段（306-326）如何调节Cdc 7与DNA的相互作用（通过其DNA合成可以被激活或失活）;以及（c）Cdc 7的氨基酸修饰如何参与Cdc 7与染色质相互作用的调节。在这里，我们建议进行深入的研究Cdc 7蛋白结构域和关键氨基酸残基内的每个域。这项工作的数据将为DNA复制的调节提供重要的新线索，并将有助于解开细胞如何保持遗传稳定性的调节机制。

The cell division process is tightly regulated and closely coordinated with copying of its genetic material (DNA). Derangement of this process can be fatal or result in genetic instability. Protein kinase known as Cdc7 plays a critical role in this regulation by connecting the cell cycle engine (i.e., cyclin-dependent kinase) and the replication machinery (i.e., the enzymes copying DNA). To perform its function, Cdc7 must enter the nucleus and then bind to chromatin (i.e., DNA) where DNA replication starts. By mutation analysis, we previously found that the amino acid segment 203-370 contains the signal for the Cdc7 nuclear import. We also found that the segment 306-326 contained a signal for the Cdc7 nuclear retention, probably by binding to chromatin where new DNA synthesis begins. This nuclear retention signal is apparently antagonized by two small segments at the carboxyl terminus of Cdc7 protein, which we collectively term a nuclear export sequence. At present, we do not know: (a) if the signals for the nuclear import and retention are one integrated or two separate elements; (b) how the 21-amino acid segment (306-326) of the nuclear retention sequence regulates the interaction of Cdc7 with DNA (by which DNA synthesis may be activated or inactivated); and (c) how the amino acid modifications of Cdc7 is involved in the regulation of Cdc7 interactions with chromatin. We here propose to carry out an in-depth study of Cdc7 protein domains and critical amino acid residues within each domain. Data from this work will shed important new light on the regulation of DNA replication, and will help to unravelling the regulation mechanism as to how a cell maintains genetic stability.