Yes, p21 is indeed a protein.
p21 (also known as WAF1, CIP1, or SD11) is a protein that plays a crucial role in regulating the cell cycle. Specifically, it functions as an inhibitor of cyclin-dependent kinases (CDKs), which are essential for cell cycle progression. By inhibiting CDKs, p21 effectively halts the cell cycle, preventing cells from dividing. This function is particularly important in response to DNA damage or other cellular stresses, allowing the cell time to repair itself or undergo apoptosis if the damage is irreparable.
In addition to its role in cell cycle arrest, p21 has also been shown to inhibit apoptosis (programmed cell death) induced by various stimuli. This dual functionality highlights the complex role of p21 in cellular processes related to proliferation and survival.
