Cell division cycle 7-related protein kinase
Cell division cycle 7-related protein kinase is an enzyme that in humans is encoded by the CDC7 gene. The Cdc7 kinase is involved in regulation of the cell cycle at the point of chromosomal DNA replication. The gene CDC7 appears to be conserved throughout eukaryotic evolution; this means that most eukaryotic cells have the Cdc7 kinase protein. The product encoded by this gene is predominantly localized in the nucleus and is a cell division cycle protein with kinase activity. The protein is a serine-threonine kinase that is activated by another protein called either Dbf4 in the yeast Saccharomyces cerevisiae or ASK in mammals. The Cdc7/Dbf4 complex adds a phosphate group to the minichromosome maintenance (MCM) protein complex allowing for the initiation of DNA replication in mitosis (as explained in the Cdc7 and Replication section below). Although expression levels of the protein appear to be constant throughout the cell cycle, the protein kinase activity appears to increase during S phase. It has been suggested that the protein is essential for initiation of DNA replication and that it plays a role in regulating cell cycle progression. Overexpression of this gene product may be associated with neoplastic transformation for some tumors. Additional transcript sizes have been detected, suggesting the presence of alternative splicing. The gene, CDC7, is involved in the regulation of cell cycle because of the gene product Cdc7 kinase. The protein is expressed at constant levels throughout the cell cycle. The gene coding for the Dbf4 or ASK protein is regulated during the different phases of cell cycle. The concentration of Dbf4 at the G1/S transition of the cell cycle is higher than the concentration at the M/G1 transition. This tells us that Dbf4 is expressed around the time for replication; right after replication is over, the protein levels drop. Because the two proteins, Cdc7 and Dbf4, must form a complex before activating the MCM complex, the regulation of one protein is sufficient for both.
