Growth Factors Growth Factors G rowth factors are gene products that play important roles in the regulation of cell division and tissue proliferation. Each growth factor has a specific cell-surface receptor. Binding of a growth factor to its receptor initiates or, in some cases, blocks cell division. Most growth factors regulate only certain types of cells and tissues. Mitosis , for example, will not occur in the presence of active inhibition and the absence of stimulation.
Growth factors regulate defined phases of the cell cycle.
An important growth factor regulating the transition from G 1 to S is insulin-like growth factor, IGF1. A growth factor receptor is activated by binding to a specific growth factor at the cell's surface. The activated receptor, in turn, activates an intracellular protein, or substrate. In turn, Ras triggers a short, time-limited signal initiating cell division. Class III consists of a large group of intracellular signal transmitters, or transducers, belonging to different families, for example, Ras proteins and protein kinases such as Src.