M-phase inducer phosphatase 1 also known as dual specificity phosphatase Cdc25A is a protein that in humans is encoded by the cell division cycle 25 homolog A (CDC25A) gene.
M-phase inducer phosphatase 1 also known as dual specificity phosphatase Cdc25A is a protein that in humans is encoded by the cell division cycle 25 homolog A (CDC25A) gene.
CDC25A is a member of the CDC25 family of dual-specificity phosphatases.
Dual-specificity protein phosphatases remove phosphate groups from phosphorylated tyrosine and serine / threonine residues. They represent a subgroup of the tyrosine phosphatase family (as opposed to the serine/threonine phosphatase family).
All mammals examined to date have three homologues of the ancestral Cdc25 gene (found e.g. in the fungus species S. pombe ), designated Cdc25A, Cdc25B, and Cdc25C. In contrast, some invertebrates harbour two (e.g., the Drosophila proteins String and Twine) or four (e.g., C. elegans Cdc-25.1 - Cdc-25.4) homologues. CDC25A is required for progression from G1 to the S phase of the cell cycle, but also plays roles in later cell cycle events. In particular, it is stabilized in metaphase cells and is degraded upon metaphase exit akin to Cyclin B. It is competent to activate the G1/S cyclin-dependent kinases CDK4 and CDK2 by removing inhibitory phosphate groups from adjacent tyrosine and threonine residues; it can also activate Cdc2 (Cdk1), the principal mitotic Cdk.
CDC25A is specifically degraded in response to DNA damage, resulting in cell cycle arrest. Thus, this degradation represents one axis of a DNA damage checkpoint, complementing induction of p53 and p21 in the inhibition of CDKs. CDC25A is considered an oncogene, as it can cooperate with oncogenic RAS to transform rodent fibroblasts, and it is overexpressed in tumours from a variety of tissues, including breast and head & neck tumours. It is a target of the E2F family of transcription factors. Therefore, its overexpression is a common consequence of dysregulation of the p53-p21-Cdk axis in carcinogenesis. [5]
CDC25A has been shown to interact with:
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. It is one of three main cell cycle checkpoints, the other two being the G2-M DNA damage checkpoint and the spindle checkpoint.
Cdc25 is a dual-specificity phosphatase first isolated from the yeast Schizosaccharomyces pombe as a cell cycle defective mutant. As with other cell cycle proteins or genes such as Cdc2 and Cdc4, the "cdc" in its name refers to "cell division cycle". Dual-specificity phosphatases are considered a sub-class of protein tyrosine phosphatases. By removing inhibitory phosphate residues from target cyclin-dependent kinases (Cdks), Cdc25 proteins control entry into and progression through various phases of the cell cycle, including mitosis and S ("Synthesis") phase.
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. Progression through these checkpoints is largely determined by the activation of cyclin-dependent kinases by regulatory protein subunits called cyclins, different forms of which are produced at each stage of the cell cycle to control the specific events that occur therein.
Tyrosine-protein phosphatase non-receptor type 11 (PTPN11) also known as protein-tyrosine phosphatase 1D (PTP-1D), Src homology region 2 domain-containing phosphatase-2 (SHP-2), or protein-tyrosine phosphatase 2C (PTP-2C) is an enzyme that in humans is encoded by the PTPN11 gene. PTPN11 is a protein tyrosine phosphatase (PTP) Shp2.
Cyclin-dependent kinase 2, also known as cell division protein kinase 2, or Cdk2, is an enzyme that in humans is encoded by the CDK2 gene. The protein encoded by this gene is a member of the cyclin-dependent kinase family of Ser/Thr protein kinases. This protein kinase is highly similar to the gene products of S. cerevisiae cdc28, and S. pombe cdc2, also known as Cdk1 in humans. It is a catalytic subunit of the cyclin-dependent kinase complex, whose activity is restricted to the G1-S phase of the cell cycle, where cells make proteins necessary for mitosis and replicate their DNA. This protein associates with and is regulated by the regulatory subunits of the complex including cyclin E or A. Cyclin E binds G1 phase Cdk2, which is required for the transition from G1 to S phase while binding with Cyclin A is required to progress through the S phase. Its activity is also regulated by phosphorylation. Multiple alternatively spliced variants and multiple transcription initiation sites of this gene have been reported. The role of this protein in G1-S transition has been recently questioned as cells lacking Cdk2 are reported to have no problem during this transition.
Mitogen-activated protein kinase 1, also known as ERK2, is an enzyme that in humans is encoded by the MAPK1 gene.
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 ; phosphorylation of these proteins leads to cell cycle progression.
Transcription factor E2F1 is a protein that in humans is encoded by the E2F1 gene.
Tyrosine-protein phosphatase non-receptor type 6, also known as Src homology region 2 domain-containing phosphatase-1 (SHP-1), is an enzyme that in humans is encoded by the PTPN6 gene.
G2/mitotic-specific cyclin-B1 is a protein that in humans is encoded by the CCNB1 gene.
The cell division cycle protein 20 homolog is an essential regulator of cell division that is encoded by the CDC20 gene in humans. To the best of current knowledge its most important function is to activate the anaphase promoting complex (APC/C), a large 11-13 subunit complex that initiates chromatid separation and entrance into anaphase. The APC/CCdc20 protein complex has two main downstream targets. Firstly, it targets securin for destruction, enabling the eventual destruction of cohesin and thus sister chromatid separation. It also targets S and M-phase (S/M) cyclins for destruction, which inactivates S/M cyclin-dependent kinases (Cdks) and allows the cell to exit from mitosis. A closely related protein, Cdc20homologue-1 (Cdh1) plays a complementary role in the cell cycle.
M-phase inducer phosphatase 2 is an enzyme that in humans is encoded by the CDC25B gene.
CDK-activating kinase assembly factor MAT1 is an enzyme that in humans is encoded by the MNAT1 gene.
G1/S-specific cyclin-E1 is a protein that in humans is encoded by the CCNE1 gene.
Cell division control protein 6 homolog is a protein that in humans is encoded by the CDC6 gene.
Cyclin-A1 is a protein that in humans is encoded by the CCNA1 gene.
14-3-3 protein beta/alpha is a protein that in humans is encoded by the YWHAB gene.
M-phase inducer phosphatase 3 is an enzyme that in humans is encoded by the CDC25C gene.
Membrane-associated tyrosine- and threonine-specific cdc2-inhibitory kinase also known as Myt1 kinase is an enzyme that in humans is encoded by the PKMYT1 gene.
The G2-M DNA damage checkpoint is an important cell cycle checkpoint in eukaryotic organisms that ensures that cells don't initiate mitosis until damaged or incompletely replicated DNA is sufficiently repaired. Cells with a defective G2-M checkpoint will undergo apoptosis or death after cell division if they enter the M phase before repairing their DNA. The defining biochemical feature of this checkpoint is the activation of M-phase cyclin-CDK complexes, which phosphorylate proteins that promote spindle assembly and bring the cell to metaphase.
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