Question

Understand how proteins that regulate the cell cycle can be altered (due to DNA mutation) and may lead to cancer (uncontrolled cell division). Know the role of tumor-suppressor genes and proto-oncogenes (genes are DNA segments).

Answer 1

Proteins and their products have a very critical role in regulating the cell cycle control. In this regard, the role of proto-oncogenes and tumor suppressor genes has been very widely investigated and understood. This can be elaborated as below:

Proto-oncogenes: These are the genes which are potentially cancerous in nature. These genes and their protein products are generally present in very minute amount or are altogether absent from the cells. Whenever these genes are mutated, their protein products get accumulated in the cells and they directly alter the nature of cell cycle. As a result of their accumulation, the proto-oncogenes tend to enhance cellular division by affecting a number of processes such as enhanced telomerase activity, enhanced CDK (cyclin dependent kinase) acitivities etc. As a result, the cell cycle undergoes un-regulated in nature and cancerous growth takes place.

Tumor suppressor genes: As the name suggests, these genes are generally known to suppress any tumor growth or uncontrolled cellular division in the cells. However, when mutations take place in these genes, they tend to decrease their protein products from the cell. As a result, the cell cycle regulation undergoes un-checked and hence, uncontrolled cellular division takes place. This is why most of the tumor-suppressor protein products are transcription factor-like in function.

Thus, this explains the role of protein products on regulation of cell cycle and cancerous growth.