Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.11.22 (cdc2)
 8,319 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Stage VI Xenopus oocytes are suspended at the G2/M transition of meiosis I, and represent an excellent system for the identification and examination of cell cycle regulatory proteins. Essential cell cycle regulators such as MAPK, cyclins and mos have the ability to induce oocyte maturation, causing the resumption of the cell cycle from its arrested state. We have identified the product of a novel Xenopus gene, Speedy or Spy1, which is able to induce rapid maturation of Xenopus oocytes, resulting in the induction of germinal vesicle breakdown (GVBD) and activation of M-phasepromoting factor (MPF). Spy1 activates the MAPK pathway in oocytes, and its ability to induce maturation is dependent upon this pathway. Spy1-induced maturation occurs much more rapidly than maturation induced by other cell cycle regulators including progesterone, mos or Ras, and does not require any of these proteins or hormones, indicating that Spy1-induced maturation proceeds through a novel regulatory pathway. In addition, we have shown that Spy1 physically interacts with cdk2, and prematurely activates cdk2 kinase activity. Spy1 therefore represents a novel cell cycle regulatory protein, inducing maturation through the activation of MAPK and MPF, and also leading to the premature activation of cdk2.
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PMID:Speedy: a novel cell cycle regulator of the G2/M transition. 1020 50

The decision for a cell to self-replicate requires passage from G1 to S phase of the cell cycle and initiation of another round of DNA replication. This commitment is a critical one that is tightly regulated by many parallel pathways. Significantly, these pathways converge to result in activation of the cyclin-dependent kinase, cdk2. It is, therefore, important to understand all the mechanisms regulating cdk2 to determine the molecular basis of cell progression. Here we report the identification and characterization of a novel cell cycle gene, designated Speedy (Spy1). Spy1 is 40% homologous to the Xenopus cell cycle gene, X-Spy1. Similar to its Xenopus counterpart, human Speedy is able to induce oocyte maturation, suggesting similar biological characteristics. Spy1 mRNA is expressed in several human tissues and immortalized cell lines and is only expressed during the G1/S phase of the cell cycle. Overexpression of Spy1 protein demonstrates that Spy1 is nuclear and results in enhanced cell proliferation. In addition, flow cytometry profiles of these cells demonstrate a reduction in G1 population. Changes in cell cycle regulation can be attributed to the ability of Spy1 to bind to and prematurely activate cdk2 independent of cyclin binding. We demonstrate that Spy1-enhanced cell proliferation is dependent on cdk2 activation. Furthermore, abrogation of Spy1 expression, through the use of siRNA, demonstrates that Spy1 is an essential component of cell proliferation pathways. Hence, human Speedy is a novel cell cycle protein capable of promoting cell proliferation through the premature activation of cdk2 at the G1/S phase transition.
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PMID:Human Speedy: a novel cell cycle regulator that enhances proliferation through activation of Cdk2. 1198 Sep 14

Speedy (Spy1) is a novel cell cycle regulator that binds and activates cdk2, and was originally identified as a suppressor of Rad1 deficiency in Schizosaccharomyces pombe. Here we demonstrate that overexpression of human Spy1 enhances mammalian cell viability during cellular responses to DNA damage induced by genotoxic agents such as camptothecin, cisplatin, and hydroxyurea. Clonogenic survival assays and comet assays also show that Spy1 expression enhances cell survival after DNA damage. Consistent with Spy1 having a role in the DNA damage response, endogenous Spy1 protein levels are up-regulated in response to DNA damage induced by camptothecin, cisplatin, or hydroxyurea. We found that Spy1 can activate cdk2 during the DNA damage response and that expression of a dominant-negative form of cdk2 overrides Spy1 function in damaged cells. Lastly, ablation of endogenous Spy1 expression using small interference RNA results in hypersensitization of cells to DNA damage. Together, these results demonstrate that human Spy1 mediates protection of mammalian cells against DNA damage.
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PMID:Human Spy1 promotes survival of mammalian cells following DNA damage. 1283 62

Progression through the G1/S transition commits cells to synthesize DNA. Cyclin dependent kinase 2 (CDK2) is the major kinase that allows progression through G1/S phase and subsequent replication events. p27 is a CDK inhibitor (CKI) that binds to CDK2 to prevent premature activation of this kinase. Speedy (Spy1), a novel cell cycle regulatory protein, has been found to prematurely activate CDK2 when microinjected into Xenopus oocytes and when expressed in mammalian cells. To determine the mechanism underlying Spy1-induced proliferation in mammalian cell cycle regulation, we used human Spy1 as bait in a yeast two-hybrid screen to identify interacting proteins. One of the proteins isolated was p27; this novel interaction was confirmed both in vitro, using bacterially expressed and in vitro translated proteins, and in vivo, through the examination of endogenous and transfected proteins in mammalian cells. We demonstrate that Spy1 expression can overcome a p27-induced cell cycle arrest to allow for DNA synthesis and CDK2 histone H1 kinase activity. In addition, we utilized p27-null cells to demonstrate that the proliferative effect of Spy1 depends on the presence of endogenous p27. Our data suggest that Spy1 associates with p27 to promote cell cycle progression through the G1/S transition.
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PMID:Spy1 interacts with p27Kip1 to allow G1/S progression. 1297 55

In addition to their activation via binding to cyclins, cyclin-dependent kinases (CDKs) can be activated via binding to a novel cell cycle regulator termed Speedy/Ringo, which shows no apparent similarity to cyclins. The first Speedy/Ringo protein was found to be essential for Xenopus oocyte maturation and a human homolog (Spy1, herein called Speedy/ Ringo A1) regulates S-phase entry and cell survival after DNA damage in cultured somatic cells. We have identified a Speedy/Ringo-like gene in the most primitive branching clade of chordates (Ciona intestinalis), as well as four mammalian homologs. Of the mammalian proteins, two, Speedy/Ringo A and C, bind to Cdc2 and Cdk2, whereas Speedy/Ringo B binds preferentially to Cdc2. Despite their distinct CDK-binding preferences, both Speedy/Ringo A and B can promote the maturation of Xenopus oocytes and all three Speedy/Ringo proteins can bind to and activate CDKs in vivo. These mammalian Speedy/Ringo proteins exhibit distinct tissue expression patterns, though all three are enriched in testis, consistent with the initial observation that Xenopus Speedy/Ringo functions during meiosis. Speedy/Ringo A is widely expressed in tissues and cell lines. Speedy/Ringo B expression appears to be testis-specific. Speedy/Ringo C is expressed in diverse tissues, particularly those that undergo polyploidization. All Speedy/Ringo proteins share a highly conserved approximately 140-aa domain we term the Speedy/Ringo box that is essential for CDK binding. Point mutations in this domain abolish CDK binding. Besides the central Speedy/Ringo box, Speedy/Ringo A contains a C-terminal portion, which promotes CDK activation, and an N-terminal portion, which is dispersible for both CDK binding and activation but that influences protein expression. The existence of this growing family of CDK activators suggests that Speedy/Ringo proteins may play as complex a role in cell cycle control as the diverse family of cyclins.
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PMID:Identification and comparative analysis of multiple mammalian Speedy/Ringo proteins. 1561 25

The intrinsic damage response is activated by DNA damage that arises during the cell division process. The ability of the cell to repair this damage during proliferation is important for normal cell growth and, when disrupted, may lead to increased mutagenesis and tumorigenesis. The atypical CDK activator, Spy1, was previously shown to promote cell survival, prevent apoptosis and inhibit checkpoint activation in response to DNA damage. Prior studies have shown that Spy1 is upregulated in breast carcinomas and accelerates mammary tumorigenesis in vivo. In this report, first, we demonstrate that the ability of Spy1 to inhibit apoptosis and bypass UV-induced checkpoint activation is dependent on the presence of the gene regulatory protein p53 and the CKI p21. Second, we demonstrate that Spy1 expression has the following effects: prevents repair of cyclobutane pyrimidine dimers through bypass of nucleotide excision repair; increases the cellular mutation frequency; and reduces the formation of cyclin E induced gammaH2A.X foci. Lastly, we show that knockdown of endogenous Spy1 leads to gammaH2A.X foci formation, Chk1 phosphorylation and proliferation defects, demonstrating a functional role for Spy1 in the intrinsic DNA damage response. These results also demonstrate that Spy1 fulfills a novel regulatory role in the intrinsic DNA damage response and maintains the balance between checkpoint activation, apoptosis, repair and cell cycle progression in response to exogenous or intrinsic damage. Furthermore, the overexpression of Spy1 as a contributing factor in cancer progression will most likely be confined to p53-positive cells.
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PMID:The atypical CDK activator Spy1 regulates the intrinsic DNA damage response and is dependent upon p53 to inhibit apoptosis. 1910 3

Families of cyclin-like proteins have emerged that bind and activate cyclin dependent kinases (Cdk)s, directing the phosphorylation of noncanonical Cdk substrates. One of these proteins, Spy1, has demonstrated the unique ability to directly bind and activate both Cdk1 and Cdk2, as well as binding and promoting the degradation of at least one Cdk inhibitor, p27(Kip1). Spy1 accelerates somatic cell growth and proliferation and is implicated in a number of human cancers including the breast, brain and liver. Herein we isolate key residues mediating the direct interaction with p27. We use mutants of Spy1 to determine the physiological role of direct interactions with distinct binding partners Cdk2 and p27. We demonstrate that disrupting the direct interaction with either Spy1 binding partner decreased endogenous activity of Cdk2, as well as Spy1-mediated proliferation. However, only the direct interaction with p27 was essential for Spy1-mediated effects on p27 stability. In vivo neither mutation completely prevented tumorigenesis, although each mutation slowed the rate of Spy1-mediated tumorigenesis and decreased overall tumor volumes. This work supports the conclusion that direct interaction with both p27 and Cdk2 contribute to Spy1-mediated effects on cell growth. It is important to elucidate the dynamics of these interactions and to consider these data when assessing functional outcomes.
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PMID:Direct interactions with both p27 and Cdk2 regulate Spy1-mediated proliferation in vivo and in vitro. 2675 40