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)

The activation of cyclin-dependent protein kinases (Cdks) is dependent upon site-specific phosphorylation and dephosphorylation reactions, as well as positive and negative regulatory subunits. The human Cdk-activating protein kinase (Cak1) is itself a Cdc2-related cyclin-dependent protein kinase that associates with cyclin H. The present study utilized specific anti-Cak1 antibodies and immunoaffinity chromatography to identify additional Cak1-associated proteins and potential target substrates. Immunoprecipitation of metabolically labeled human osteosarcoma cells revealed a number of Cak1-associated proteins, including p95, p37 (cyclin H), and a 35-kDa protein that was further characterized herein. Microsequence analysis obtained after limited proteolysis revealed peptide fragments that are similar, but not identical to, human and yeast cyclins, thus identifying p35 as a cyclin-like regulatory subunit. The greatest sequence similarity of human p35 is with Mcs2, a yeast cyclin that is essential for cell cycle progression. Immunoaffinity chromatography performed under nondenaturing conditions afforded the isolation of enzymatically active Cak1 from cell lysates, enabling studies of kinase autophosphorylation and comparative substrate utilization. Immunoaffinity-purified Cak1 phosphorylated monomeric Cdc2 and Cdk2, but not Cdk4; the phosphorylation of both Cdc2 and Cdk2 were increased in the presence of recombinant cyclin A. These studies indicate that the Cak1 catalytic subunit, like Cdc2 and Cdk2, associates with multiple regulatory partners and suggests that subunit composition may be an important determinant of this multifunctional enzyme.
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PMID:Biochemical characterization of the human cyclin-dependent protein kinase activating kinase. Identification of p35 as a novel regulatory subunit. 855 Jun 4

We report here the first extensive in vivo study of cell cycle regulation in the Xenopus embryo. Cyclin A1, B1, B2, and E1 levels, Cdc2 and Cdk2 kinase activity, and Cdc25C phosphorylation states were monitored during early Xenopus embryonic cell cycles. Cyclin B1 and B2 protein levels were high in the unfertilized egg, declined upon fertilization, and reaccumulated to the same level during the first cell cycle, a pattern repeated during each of the following 11 divisions. Cyclin A1 showed a similar pattern, except that its level was lower in the egg than in the cell cycles after fertilization. Cyclin B1/Cdc2 kinase activity oscillated, peaking before each cleavage, and Cdc25C alternated between a highly phosphorylated and a less phosphorylated form that correlated with high and low cyclin B1/Cdc2 kinase activity, respectively. Unlike the mitotic cyclins, the level of cyclin E1 did not oscillate during embryogenesis, although its associated Cdk2 kinase activity cycled twice for each oscillation of cyclin B1/Cdc2 activity, consistent with a role for cyclin E1 in both S-phase and mitosis. Although the length of the first embryonic cycle is regulated by both the level of cyclin B and the phosphorylation state of Cdc2, cyclin accumulation alone was rate-limiting for later cycles, since overexpression of a mitotic cyclin after the first cycle caused cell cycle acceleration. The activity of Cdc2 closely paralleled the accumulation of cyclin B2, but cell cycle acceleration caused by cyclin B overexpression was not associated with elevation of Cdc2 activity to higher than metaphase levels. Tyrosine phosphorylation of Cdc2, absent during cycles 2-12, reappeared at the midblastula transition coincident with the disappearance of cyclin E1. Cyclin A1 disappeared later, at the beginning of gastrulation. Our results suggest that the timing of the cell cycle in the Xenopus embryo evolves from regulation by accumulation of mitotic cyclins to mechanisms involving periodic G1 cyclin expression and inhibitory tyrosine phosphorylation of Cdc2.
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PMID:In vivo regulation of the early embryonic cell cycle in Xenopus. 860 1

The restriction point (R) separates two functionally different parts of G1 in continuously cycling cells. G1-pm represents the postmitotic interval of G1 that lasts from mitosis to R. G1-ps represents the pre S phase interval of G1 that lasts from R to S. G1-pm is remarkably constant in length (its duration is about three hours) in the different cell types studied so far. G1-ps, however, varies considerably, indicating that entry into S is not directly followed after passage through R. Progression through G1-pm requires continuous stimulation by mitogenic signals (e.g. growth factors) and a high rate of protein synthesis. Interruption of the mitogenic signals or moderate inhibition of protein synthesis leads to a rapid exit from the cell cycle to G0 in normal (untransformed) cells. Upon restimulation with mitogenic signals, the cell returns to the same point in G1-pm from which it left the cell cycle. Thus the cell seems to have a memory for how far it has advanced through G1-pm, suggesting that a continuous structural alteration, for example chromatin decondensation, takes place in G1. The molecular background to transition from growth factor dependence in G1-pm to growth factor independence in G1-ps (a switch which represents commitment to a new cell cycle and passage through R) is still not fully understood. Cyclin-dependent kinase (cdk)-mediated hyperphosphorylation of the retinoblastoma protein (Rb), and concomitant liberation (and activation) of members of the E2F family of transcription factors, are probably important aspects of R control in normal cells. A key component here could be cdk2 activity which is controlled by cyclin E. When cdk2 activity starts to increase rapidly in G1, due to activation of a positive feedback loop, it reaches a critical level above which cdk inhibitors (CKIs) such as p21 and p27 are outweighed; the cell has then become independent of mitogenic and inhibitory signals and is committed to a new cell cycle. However, other components are probably also involved in R control. For instance, a 'cryptic' R (a G1-pm-like state) can be induced even in tumour cells that do not respond to growth factor starvation or protein synthesis inhibitors, and are therefore probably defective in the cdk-Rb-E2F pathway. Possibly, a certain degree of chromatin decondensation has to take place after mitosis in order to allow transcription of, for example, the cyclin E gene or other critical E2F targets. Although the molecular basis for restriction point control still remains unclear, we can expect rapid progress in this important field over the next few years.
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PMID:What is the restriction point? 860 14

Activation of the cyclin-dependent kinases to promote cell cycle progression requires their association with cyclins as well as phosphorylation of a threonine (residue 161 in human p34cdc2). This phosphorylation is carried out by CAK, the Cdk-activating kinase. We have purified and cloned CAK from S. cerevisiae. Unlike CAKs from other organisms, Cak1p is active as a monomer, has full activity when expressed in E. coli, and is not a component of the basal transcription factor, TFIIH. A temperature-sensitive mutation in CAK1 confers a G2 delay accompanied by low Cdc28p protein kinase activity and shows genetic interactions with altered expression of the gene for the major mitotic cyclin, CLB2. Our data raise the intriguing possibility that p40MO15-cyclin H-MAT1, identified as the predominant CAK in vertebrate cell extracts, may not function as a physiological CAK.
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PMID:The Cdk-activating kinase (CAK) from budding yeast. 875 10

Granzyme B rapidly induces apoptosis in the presence of the pore-forming protein perforin. We have examined the cell cycle restriction of this apoptosis by separating Jurkat cells into fractions representing different stages of the cell cycle by centrifugal elutriation. Cells were susceptible to apoptosis from G1 through to G2/M, with no significant resistance detected at any stage. Similarly, cells arrested at G1/S or G2/M with either hydroxyurea or nocodazole were slightly more sensitive than asynchronously growing cells. Granzyme B induces Cdc2 kinase activity and requires its induction for apoptosis. Cyclin-dependent kinase (CDK) activity is regulated by phosphorylation and association with cyclins that also control subcellular localization of the CDK/cyclin complexes. Cdc2 associates with both cyclin A, which is synthesized at G1 and S, and cyclin B, which is produced later during S and G2 before G2/M transition. We find that the CDK activity induced by granzyme B is associated primarily with cyclin A in both asynchronous and G1/S-arrested cells, while cyclin B-associated kinase activity is minimal. Because cyclin A is also able to associate with Cdk2, a kinase that is important for G1/S transition, we examined the activation of this CDK during granzyme B-induced apoptosis and find that Cdk2 is induced as rapidly as Cdc2. In conclusion, we have identified a lack of cell cycle restriction of granzyme B-induced apoptosis and the rapid activation of both cyclin A/Cdc2 and cyclin A/Cdk2 kinase activity.
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PMID:Granzyme B induces apoptosis and cyclin A-associated cyclin-dependent kinase activity in all stages of the cell cycle. 880 36

We have isolated Xenopus p28Kix1, a member of the p21CIP1/p27KIP1/p57KIP2 family of cyclin-dependent kinase (Cdk) inhibitors. Members of this family negatively regulate cell cycle progression in mammalian cells by inhibiting the activities of Cdks. p28 shows significant sequence homology with p21, p27, and p57 in its N-terminal region, where the Cdk inhibition domain is known to reside. In contrast, the C-terminal domain of p28 is distinct from that of p21, p27, and p57. In co-immunoprecipitation experiments, p28 was found to be associated with Cdk2, cyclin E, and cyclin A, but not the Cdc2/cyclin B complex in Xenopus egg extracts. Xenopus p28 associates with the proliferating cell nuclear antigen, but with a substantially lower affinity than human p21. In kinase assays with recombinant Cdks, p28 inhibits pre-activated Cdk2/cyclin E and Cdk2/cyclin A, but not Cdc2/cyclin B. However, at high concentrations, p28 does prevent the activation of Cdc2/cyclin B by the Cdk-activating kinase. Consistent with the role of p28 as a Cdk inhibitor, recombinant p28 elicits an inhibition of both DNA replication and mitosis upon addition to egg extracts, indicating that it can regulate multiple cell cycle transitions. The level of p28 protein shows a dramatic developmental profile: it is low in Xenopus oocytes, eggs, and embryos up to stage 11, but increases approximately 100-fold between stages 12 and 13, and remains high thereafter. The induction of p28 expression temporally coincides with late gastrulation. Thus, although p28 may play only a limited role during the early embryonic cleavages, it may function later in development to establish a somatic type of cell cycle. Taken together, our results indicate that Xenopus p28 is a new member of the p21/p27/p57 class of Cdk inhibitors, and that it may play a role in developmental processes.
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PMID:Cell cycle control by Xenopus p28Kix1, a developmentally regulated inhibitor of cyclin-dependent kinases. 886 73

A protein present in extracts of the dinoflagellate Gonyaulax that was capable of binding an antibody directed against the conserved Cdc2 kinase epitope EGVPSTAIREISLLKE was characterized by Western blot analysis and DNA sequencing and shown not to encode a Cdc2 kinase. The amount, size, and isoelectric point of the immunoreactive species were invariant over a 24-hour period (encompassing S and M phases), and the DNA sequence of a cDNA isolated by immunologic screening showed that no conserved kinase regions were present in the deduced amino acid sequence. A method based on polymerase chain reaction (PCR), using primers designed from conserved regions in the Cdc2 kinases, was also unsuccessful in isolating a cdc2 gene homologue, although other kinases were identified.
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PMID:Do dinoflagellates contain a Cdc2-like protein kinase? 886 17

The cross-linking of surface immunoglobulins (sIg) of B cells can transmit a negative signal, resulting in cell cycle arrest, apoptosis or both. Signaling via the B cell antigen CD40 reverses the sIg-mediated negative signaling and induces activation and proliferation of B cells. We investigated the molecular mechanism for cell cycle regulation by negative and positive signaling via sIg and CD40, respectively, by using the B cell line WEHI-231. Cross-linking of sIg almost completely reduced the activity of cyclin-dependent kinase (Cdk) 2, essential for cell cycle progression in the late G1 phase, although the level of Cdk2 was not reduced. Among the factors that regulate Cdk2 activation, the activity of the Cdk-activating kinase (CAK) appeared intact and cyclin E was reduced only partially in sIg-cross-linked WEHI-231. In contrast, sIg cross-linking induced a significant Cdk inhibitor (CKI) activity. Since a 27-kDa protein was co-precipitated with Cdk2 in anti-Ig-treated, but not untreated WEHI-231, and the CKI activity in anti-Ig-treated WEHI-231 was neutralized by anti-p27Kip1 antibodies, it is most likely that p27Kip1 is responsible for the CKI activity induced by sIg cross-linking. p27Kip1 may thus play a role in growth inhibition of B cells by negative signaling via sIg. In contrast, CD40 signaling enhanced Cdk2 activity and reduced the p27Kip1 level in anti-Ig-treated WEHI-231, suggesting that the reduction of p27Kip1 plays an important role in the abrogation of sIg-mediated growth arrest by CD40 signaling. Taken together, p27Kip1 is likely to be a crucial target molecule of the negative signaling via sIg and the positive signaling via CD40 essential for T cell-dependent immune responses.
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PMID:Differential modulation of cyclin-dependent kinase inhibitor p27Kip1 by negative signaling via the antigen receptor of B cells and positive signaling via CD40. 889 56

Apoptosis has recently been hypothesized to be the result of aberrant cell cycle control. In this study, we have investigated the role of cell cycle-regulatory elements in Fas-induced apoptosis of hematopoietic cells. When HL-60 cells were treated with anti-Fas antibody, rapid activation of growth-associated histone H1 kinase was observed without any change in cell cycle distribution. This was accompanied by the increase in cdc2 mRNA expression and Cdc2 kinase activity. Up-regulation of cdc2 mRNA was similarly induced in BCL-2-overexpressing HL-60 subline by anti-Fas treatment independently of the appearance of apoptotic phenotypes. Fas-induced apoptosis was completely inhibited by butyrolactone I, a specific inhibitor of Cdc2 kinase. Moreover, the same phenomenon was observed during Fas-induced but not spontaneous apoptosis of postmitotic granulocytes. Finally, we have found that "Fas-responsive element" was located between nucleotides -730 and -552 of the cdc2 promoter and was responsive for transcriptional activation of the cdc2 gene during Fas-induced apoptosis. These results indicate that aberrant activation of Cdc2 is associated with Fas-induced apoptosis of hematopoietic cells, and that the mechanism of cdc2 transcription during Fas-induced apoptosis is different from that in normal cell cycle control.
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PMID:Transcriptional activation of the cdc2 gene is associated with Fas-induced apoptosis of human hematopoietic cells. 891 Apr 74

Cyclin-dependent kinase (Cdk) enzymes are activated for entry into the S phase of the cell cycle. Elimination of Cdk inhibitor protein p27Kip1 during the G1 to S phase is required for the activation process. An inhibitor of 3-hydroxy-3-methylglutaryl-CoA reductase prevents its elimination and leads to G1 arrest. Mevalonate and its metabolite, geranylgeranyl pyrophosphate, but not farnesyl pyrophosphate, restore the inhibitory effect of pravastatin on the degradation of p27 and allow Cdk2 activation. By the addition of geranylgeranyl pyrophosphate, Rho small GTPase(s) are geranylgeranylated and translocated to membranes during G1/S progression. The restoring effect of geranylgeranyl pyrophosphate is abolished with botulinum C3 exoenzyme, which specifically inactivates Rho. These results indicate (i) among mevalonate metabolites, geranylgeranyl pyrophosphate is absolutely required for the elimination of p27 followed by Cdk2 activation; (ii) geranylgeranylated Rho small GTPase(s) promote the degradation of p27 during G1/S transition in FRTL-5 cells.
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PMID:Geranylgeranylated rho small GTPase(s) are essential for the degradation of p27Kip1 and facilitate the progression from G1 to S phase in growth-stimulated rat FRTL-5 cells. 899 16


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