Cell cycle inhibitory proteins are encoded by
The correct answer and explanation is:
Cell cycle inhibitory proteins are encoded by tumor suppressor genes. These proteins regulate the progression of the cell cycle, ensuring that cells do not divide uncontrollably, which is a characteristic of cancer cells. Tumor suppressor genes produce proteins that act as checkpoints to halt the cell cycle if any DNA damage or other irregularities are detected.
One of the most well-known tumor suppressor genes is TP53, which encodes the p53 protein. The p53 protein plays a crucial role in maintaining genomic stability by responding to DNA damage. When DNA damage is detected, p53 can activate genes that either repair the damage or induce cell death (apoptosis) if the damage is irreparable. In this way, p53 helps prevent the proliferation of cells with damaged DNA, which could lead to cancer.
Another important class of cell cycle inhibitors are cyclin-dependent kinase inhibitors (CKIs). These include proteins like p21, p27, and p16. These CKIs bind to cyclin-dependent kinases (CDKs), which are enzymes that drive the progression of the cell cycle by adding phosphate groups to other proteins. By inhibiting CDKs, CKIs prevent cells from advancing through the cell cycle inappropriately, thus maintaining proper control over cell division.
The function of these inhibitory proteins is critical because unchecked cell cycle progression is a hallmark of cancer. Mutations in tumor suppressor genes like TP53 or the loss of CKIs can result in cells bypassing critical checkpoints, leading to the uncontrolled proliferation that is characteristic of cancer. Consequently, these proteins are often studied for their potential in cancer therapies, aiming to restore or mimic their function to stop tumor growth.
In summary, cell cycle inhibitory proteins are encoded by tumor suppressor genes, and their role in halting the cell cycle at various checkpoints is essential for preventing cancer and maintaining healthy cell division.