Concept
P21
Related concepts (16)
Restriction point
The restriction point (R), also known as the Start or G1/S checkpoint, is a cell cycle checkpoint in the G1 phase of the animal cell cycle at which the cell becomes "committed" to the cell cycle, and after which extracellular signals are no longer required to stimulate proliferation. The defining biochemical feature of the restriction point is the activation of G1/S- and S-phase cyclin-CDK complexes, which in turn phosphorylate proteins that initiate DNA replication, centrosome duplication, and other early cell cycle events.
Cyclin A
Cyclin A is a member of the cyclin family, a group of proteins that function in regulating progression through the cell cycle. The stages that a cell passes through that culminate in its division and replication are collectively known as the cell cycle Since the successful division and replication of a cell is essential for its survival, the cell cycle is tightly regulated by several components to ensure the efficient and error-free progression through the cell cycle.
S phase
S phase (Synthesis Phase) is the phase of the cell cycle in which DNA is replicated, occurring between G1 phase and G2 phase. Since accurate duplication of the genome is critical to successful cell division, the processes that occur during S-phase are tightly regulated and widely conserved. G1/S transition Entry into S-phase is controlled by the G1 restriction point (R), which commits cells to the remainder of the cell-cycle if there is adequate nutrients and growth signaling.
Cyclin-dependent kinase inhibitor 1C
Cyclin-dependent kinase inhibitor 1C (p57, Kip2), also known as CDKN1C, is a protein which in humans is encoded by the CDKN1C imprinted gene. Cyclin-dependent kinase inhibitor 1C is a tight-binding inhibitor of several G1 cyclin/Cdk complexes and a negative regulator of cell proliferation. Mutations of CDKN1C are implicated in sporadic cancers and Beckwith-Wiedemann syndrome suggesting that it is a tumor suppressor candidate. CDKN1C is a tumor suppressor human gene on chromosome 11 (11p15) and belongs to the cip/kip gene family.
G0 phase
DISPLAYTITLE:G0 phase The G0 phase describes a cellular state outside of the replicative cell cycle. Classically, cells were thought to enter G0 primarily due to environmental factors, like nutrient deprivation, that limited the resources necessary for proliferation. Thus it was thought of as a resting phase. G0 is now known to take different forms and occur for multiple reasons. For example, most adult neuronal cells, among the most metabolically active cells in the body, are fully differentiated and reside in a terminal G0 phase.
P16
p16 (also known as p16INK4a, cyclin-dependent kinase inhibitor 2A, CDKN2A, multiple tumor suppressor 1 and numerous other synonyms), is a protein that slows cell division by slowing the progression of the cell cycle from the G1 phase to the S phase, thereby acting as a tumor suppressor. It is encoded by the CDKN2A gene. A deletion (the omission of a part of the DNA sequence during replication) in this gene can result in insufficient or non-functional p16, accelerating the cell cycle and resulting in many types of cancer.
MyoD
MyoD, also known as myoblast determination protein 1, is a protein in animals that plays a major role in regulating muscle differentiation. MyoD, which was discovered in the laboratory of Harold M. Weintraub, belongs to a family of proteins known as myogenic regulatory factors (MRFs). These bHLH (basic helix loop helix) transcription factors act sequentially in myogenic differentiation. Vertebrate MRF family members include MyoD1, Myf5, myogenin, and MRF4 (Myf6). In non-vertebrate animals, a single MyoD protein is typically found.
G2 phase
DISPLAYTITLE:G2 phase G2 phase, Gap 2 phase, or Growth 2 phase, is the third subphase of interphase in the cell cycle directly preceding mitosis. It follows the successful completion of S phase, during which the cell’s DNA is replicated. G2 phase ends with the onset of prophase, the first phase of mitosis in which the cell’s chromatin condenses into chromosomes. G2 phase is a period of rapid cell growth and protein synthesis during which the cell prepares itself for mitosis.
Cell cycle checkpoint
Cell cycle checkpoints are control mechanisms in the eukaryotic cell cycle which ensure its proper progression. Each checkpoint serves as a potential termination point along the cell cycle, during which the conditions of the cell are assessed, with progression through the various phases of the cell cycle occurring only when favorable conditions are met. There are many checkpoints in the cell cycle, but the three major ones are: the G1 checkpoint, also known as the Start or restriction checkpoint or Major Checkpoint; the G2/M checkpoint; and the metaphase-to-anaphase transition, also known as the spindle checkpoint.
Cyclin-dependent kinase 1
Cyclin-dependent kinase 1 also known as CDK1 or cell division cycle protein 2 homolog is a highly conserved protein that functions as a serine/threonine protein kinase, and is a key player in cell cycle regulation. It has been highly studied in the budding yeast S. cerevisiae, and the fission yeast S. pombe, where it is encoded by genes cdc28 and cdc2, respectively. With its cyclin partners, Cdk1 forms complexes that phosphorylate a variety of target substrates (over 75 have been identified in budding yeast); phosphorylation of these proteins leads to cell cycle progression.