Final answer:
The anaphase promoting complex/cyclosome (APC/C) is the protein that adds ubiquitins to cyclin, aiding in its degradation following its role in cell cycle regulation together with cyclin-dependent kinases (Cdks). This regulatory mechanism is essential for proper cell division and prevents uncontrolled cell proliferation like cancer.
Step-by-step explanation:
In cell division, a protein called anaphase promoting complex/cyclosome (APC/C) adds ubiquitins to cyclin and other proteins involved in the regulation of mitosis. This process is crucial for the cell cycle's regulation. Proteins called cyclins and cyclin-dependent kinases (Cdks) play significant roles in the positive regulation of this cycle, ensuring the cell progresses through various checkpoints.
Cyclins, of which there are four major types, have concentrations that fluctuate throughout the cell cycle. When a cell advances to a new stage, the cyclins from the previous stage are marked for degradation. This degradation is facilitated by the ubiquitin system, where ubiquitin molecules act as flags, signaling that the protein's lifespan is complete. The proteins tagged with ubiquitin are then directed to the proteasome to be broken down.
Within this context, cell cycle checkpoints are governed by complex interactions among multiple molecules, including the aforementioned cyclins and Cdks, to ensure that a cell only proceeds to the next phase of the cycle when certain conditions have been met. This molecular regulation is critical for maintaining healthy cell proliferation and preventing diseases like cancer, which are characterized by uncontrolled cell division due to dysregulation of these processes.