The process of cell division depends on the proper activity of cell cycle regulators. If these proteins are altered, they can override a cell cycle checkpoint. A mutation can also increase the activity of a positive regulator. For example, a mutation that causes Cdk to become activated without cyclin could push the cell cycle past the checkpoint before all conditions were met. This type of mutation will prevent the daughter cells from propagating, but if they are able to undergo further cell divisions, the mutations may accumulate in these cells and eventually lead to the subsequent generation.
The cell cycle has several checkpoints to regulate the process. The first checkpoint occurs just before the cell moves into the S phase, which is where the DNA is replicated. This checkpoint helps the cell determine whether it has enough nutrients and does not have DNA damage. It also activates proteins in the cell, which then trigger signal transduction pathways and tells the cell to continue or stop the cell cycle.
Cancer is caused by unchecked cell division. When this monitoring system fails, mistakes in cell replication are passed onto daughter cells. A small percentage of these errors will cause a faulty protein to be produced. This mutation results in cancer. It can also trigger leukemia or tumor growth.
One of the most important aspects of the cell cycle is its regulation. Without it, cancer cells could develop into dangerous tumors. This is one reason why cancer is so common. It is difficult to identify the primary cause of cancer because cells become too numerous. Several studies have been published that address the importance of cell cycle regulation.
The cell cycle control mechanism also includes checkpoint control, a type of supervisory regulation. While not a necessary component of the cell cycle-progression machinery, checkpoints sense flaws in critical events such as DNA replication and chromosome segregation. They send a signal to the cell cycle machinery to delay the cell cycle until the risk of mutations has been removed.
During the cell cycle, the cyclin protein seeks out the cyclin-dependent kinase (CDK) molecule. When this protein binds to the CDK, it initiates a phosphorylation cascade. The phosphorylated CDK then transfers phosphate groups to a number of other proteins. The phosphate groups on the CDK are transferred to a number of other proteins, which in turn activate a cellular response and drive the cell cycle forward.
Cyclins are serine/threonine protein kinases that phosphorylate key substrates during the cell cycle. These enzymes are tightly regulated at the synthesis and proteolysis stages of the cell cycle. Their activity can be negatively regulated by inhibitory tyrosine phosphorylation, which blocks phosphate transfer to their substrates.