induced tumor suppressors a GRIM story Biology Diagrams The tumor suppressor protein p53 also regulates progression through the G1 checkpoint of the cell-cycle. In particular, p53 is activated in response to DNA damage and serves to arrest cell-cycle progression in G1 and hence allow time for DNA repair.
The products of the Rb and INK4 tumor suppressor genes regulate cell cycle progression at the same point as that affected by cyclin D1 (Figure 15.38). Rb inhibits passage through the restriction point in G 1 by repressing transcription of a number of genes involved in cell cycle progression and DNA synthesis (see Figure 14.20). In normal cells Tumor suppressor genes encode proteins that normally inhibit tumor formation caused by abnormal cellular proliferation. Tumor suppressor proteins can participate in a variety of processes such as negative regulation of the cell cycle, positive regulation of apoptosis, regulation of DNA damage response, or other mechanisms (Stanbridge, 1990
Tumor suppressor gene Biology Diagrams
When something goes wrong with a tumor suppressor gene, such as a pathogenic variant (mutation) that stops it from working, cell division can get out of control. Inherited changes in tumor suppressor genes have been found in some family cancer syndromes. They cause certain types of cancer to run in families. But most tumor suppressor gene In contrast to the cellular proliferation-stimulating function of proto-oncogenes and oncogenes that drive the cell cycle forward, tumor suppressor genes code for proteins that normally operate to
Both, in balance, regulate the whole cell cycle activities. Proto-oncogenes prevent cells from undergoing apoptosis, on the other side, tumor suppressor genes force cells to undergo apoptosis, if damaged. Note that apoptosis is a programmed cell death process that is also necessary for healthy cell cycle activities.
Suppressor Genes Biology Diagrams
Checkpoints are depicted as thick red bars. The stages of the cell cycle (G1: Gap 1, S: DNA synthesis, G2: Gap 2, and M: mitosis) are indicated. Tumor suppressors act to maintain checkpoints
