The p53 gene may be the most important gene preventing human cancer. This gene i

Question

The p53 gene may be the most important gene preventing human cancer. This gene is mutated in about half of all cancers (and the pathway in which it participates is mutated in essentially all cancers).

A. We can envisage two mechanisms to increase the amount of p53 protein when it is suddenly needed. First, transcription and translation of the p53 gene might be low in the absence of a stimulus and markedly increased after stimulation. Second, transcription and translation of the p53 gene might be high at all times, but the protein amount is normally low as a result of proteolytic degradation; after stimulation, degradation is inhibited and consequently the protein amount increases. The latter mechanism is actually used by cells. Suggest the most important advantage of this mechanism. B. List two of the four major classes of stimuli that evoke increased p53 amounts in normal human cells.

Explanation / Answer

A. The protein undergoes degradation if stimulation is not received. The advantage of this type of regulation is IT IS REVERSIBLE, quick, and efficient. The dose of gene product can be altered at the level of cytoplasm itself, since an actiator binding to a receptor in the cytoplasm is sufficient to regulate the process. The enzyme that degrades the protein may be activated by a simple phosphrylation, and can be deactivated by removal of phosphate groups. otherwise, the gene product itself may be phosphorylated or dephosphorylate to control its own dose. This mechanism of activation and deactivation can be regulated easily and reversibly.

B. Cellular stress due to DNA damage, High cell density - mediated through Cispt

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