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

Cell cycle regulators such as cyclins, cyclin-dependent kinases (cdks) and their inhibitors control the growth of cells. SDI1/CIP1/WAF1/p21 is a potent inhibitor of G1 cdks, whose expression is induced by wild-type p53. To elucidate the mechanism of growth inhibition by transforming growth factor beta 1 (TGFbeta 1), we examined the effect of TGFbeta 1 on the expression of p21, G1 cyclins and cdks by human gastric cancer cell lines. TGFbeta 1 induced p21 expression and subsequently suppressed cdk2 kinase activity, followed by a reduction in phosphorylation of the product of the retinoblastoma tumor suppressor gene in TMK-1 cells, which are responsive to TGFbeta 1. Coimmunoprecipitation analysis demonstrated that TGFbeta 1 increased the level of p21 protein present in complexes with cdk2. In contrast, TGFbeta 1 did not induce p21 in TGFbeta 1-resistant MKN-28 cells. TGFbeta 1 did not affect the levels of p53 mRNA and protein in TMK-1 and MKN-28 cells, which contain mutated p53 genes. These mutated p53 complementary DNAs, when overexpressed, failed to activate transcription from the p21 promoter. Furthermore, TGFbeta 1 caused a reduction in the steady-state level of cyclin A protein concomitantly with inhibition of cdk2 kinase activity in TMK-1 cells. These results suggest that the growth inhibition of tumor cells by TGFbeta 1 is associated with p53-independent induction of p21, subsequent suppression of cdk activity and a decrease in cyclin A protein in TMK-1 cells.
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PMID:Inhibition of cell growth by transforming growth factor beta 1 is associated with p53-independent induction of p21 in gastric carcinoma cells. 864 69

Cyclin-dependent kinases (Cdks) form complexes with cyclins, and as a consequence they generally express kinase activities. One of these Cdks, Cdk2, is known to bind with cyclins A and E, and plays an important role in the progression of the cell cycle via phosphorylation of target proteins such as the product of the retinoblastoma tumor-suppressor gene (pRB). It has been suggested that Cdk2 bound with cyclin D1 and Cdk2-cyclin-D1 complex show neither H1 histone nor pRB kinase activity. However, it is not clear whether Cdk2-cyclin-D1 has unknown targets and why Cdk2 is not activated by binding with cyclin D1. We investigated these questions using Cdk, cyclin and Cdk-cyclin complexes produced in a baculovirus expression system. Cdk2 formed a complex with cyclin D1 in this system. After extensive purification, Cdk2 was still bound to cyclin D1. The Cdk2-cyclin-D1 complex did not phosphorylate any tested substrates, such as H1 histone, pRB, SV40 large T antigen, p53, E2F-1 or a preparation of nuclear proteins from HeLa cells; in contrast, Cdk2-cyclin-E and Cdk2-cyclin-A phosphorylated these proteins. Moreover, the Cdk2-cyclin-D1 complex was not activated by incubation with Cdk4 or cyclin E. Thus, Cdk2 and cyclin D1 formed a stable complex that was not activated. In order to determine why Cdk2-cyclin-D1 lacks kinase activity, we investigated the phosphorylation of Cdk2. Under-shifted Cdk2, the active form of Cdk2, was not detected in the Cdk2-cyclin-D1 complex in the baculovirus system. In human WI-38 cells, cyclin D1 began to form a complex with Cdk2 as well as with Cdk4 from the mid-G1 phase of the cell cycle. The Cdk2 bound to cyclin D1 in human cells was also the inactive form that was slowly migrated. Moreover, we found that Cdk2 bound to cyclin D1 was not phosphorylated by Cdk7-cyclin-H, while Cdk2 bound to cyclin E, as well as free Cdk2, was was phosphorylated by Cdk7-cyclin-H. Additionally, Cdk2 phosphorylated by Cdk7-cyclin-H did not bind to cyclin D1. These results strongly suggest that Cdk2 forms a stable complex with cyclin D1 but is not activated because the Cdk2 molecule in the complex is not phosphorylated by Cdk7-cyclin-H and the phosphorylated Cdk2, an active form, does not bind to cyclin D1.
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PMID:Cyclin-dependent kinase-2 (Cdk2) forms an inactive complex with cyclin D1 since Cdk2 associated with cyclin D1 is not phosphorylated by Cdk7-cyclin-H. 864 86

In vitro models of malignant transformation of human cells may provide considerable insight into the mechanisms of multi-step carcinogenesis. It is well established that normal human cells must be immortalized before they can be malignantly transformed; however, they are stringently destined for aging and are rarely immortalized. The mechanism of cellular aging and immortalization is still unknown. We detected expression of only mutated p53 mRNA by direct sequencing of the reverse-transcribed mRNA in 3 human cell lines immortalized either with 4-nitroquinoline 1-oxide or with 60Co gamma rays. Consequently, only the mutated pS3 protein was expressed in each immortalized cell line. The expression of sdiI/p21 and mdm2, both of which are positively regulated by wild-type p53, was significantly down-regulated in the immortalized cell lines, resulting in over-expression of cdk2 and cdk4. Introduction of the sdiI/p21 gene into these cells was followed by a remarkable decrease in their ability to synthesize DNA. These results indicate that the p53 cascade may play an important role in the immortalization of human cells.
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PMID:Mutation in p53 and de-regulation of p53-related gene expression in three human cell lines immortalized with 4-nitroquinoline 1-oxide or 60Co gamma rays. 864 35

Normal keratinocytes from epidermis and from buccal mucosa underwent dissimilar stages of differentiation in the same culture medium and responded differently to changes in the composition of the medium. Manifestations of these variations were examined in terms of the expression at the mRNA level (as measured by reverse transcriptase-polymerase chain reaction) of three regulatory genes (cdc2, c-myc, and p53) and five that encode structural proteins (keratins K5, K10 and K13, involucrin, and filaggrin), in three growth-medium formulations. The culture conditions enhanced or retarded maturation; the observed alterations in gene expression correlated with these changes. Except for the proliferation genes, the non-keratinizing buccal mucosa generally responded more weakly than the orthokeratotic epidermis to culture-medium supplementation favouring differentiation. Gene expression in cultured keratinocytes reflected their ability to differentiate in vivo; genes were expressed even when the corresponding protein was not seen in vitro. Although keratin K10 is not prevalent in the buccal mucosa nor keratin K13 in the epidermis, the genes for both were found to be expressed in both tissues.
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PMID:Gene expression of markers associated with proliferation and differentiation in human keratinocytes cultured from epidermis and from buccal mucosa. 865 90

The p21WAF-1 gene is positively regulated by the wild-type p53 protein. p21WAF-1 has been shown to interact with several cyclin-dependent kinase complexes and block the activity of G1 cyclin-dependent kinases (cdks). Mutational analysis with the p21WAF-1 gene localized a site, at amino acid residues 21 and 24 in the amino terminus of the protein, for p21WAF-1 binding to cyclins D and E. This region of the protein is conserved (residues 21 to 26) in other p21WAF-1 family members, p27kip-1 and p57kip-2. The same p21WAF-121,24 mutant also fails to bind to cyclin D1-cdk 4 or cyclin E-cdk 2 complexes in vitro, suggesting that amino acid residues 21 and 24 are important for p21WAF-1-cdk-cyclin trimeric complex interactions. The p21WAF-1 wild-type protein will suppress tumor cell growth in culture while p21WAF-1 mutant proteins with defects in residues 21 and 24 fail to suppress tumor cell growth. The overexpression of cyclin D or E in these cells will partially overcome the growth suppression of wild-type p21WAF-1 protein in cells. These results provide evidence that p21WAF-1 acts through cyclin D1-cdk4 and cyclin E-cdk2 complexes in vivo to induce the growth suppression. The p21WAF-1 binding sites for cyclins (residues 21 to 26), cdk2 (residues 49 to 71), and proliferating-cell nuclear antigen (residues 124 to 164) have all been mapped to discrete sites on the protein.
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PMID:Analysis of wild-type and mutant p21WAF-1 gene activities. 865 54

The cyclin-dependent kinase (CDK) inhibitor p21 is induced by the tumor suppressor gene product p53 and is thought to be important for the arrest of the cell cycle following DNA damage. Here we have investigated the contribution of p21 in inhibiting different cyclin-CDK complexes that drive different cell cycle transitions following UV irradiation-induced DNA damage in normal human fibroblasts and immortalized rodent fibroblasts. When cells were exposed to a low dose of UV irradiation, both p53 and p21 were induced; the protein kinase activities associated with Cdc2, Cdk2, and Cdk4 were inhibited; and there was a good correlation between their inhibition and binding to p21. p21 alone is likely to be sufficient for the inhibition of Cdk2 because all the cyclin-complexed forms of Cdk2 were associated with p21 after irradiation. In contrast, only a small proportion of Cdk4 and Cdc2 was complexed with p21, although the level of Cdk4 associated with either p21 or p27 was increased after irradiation. Furthermore, recombinant p21 added to an unirradiated cell lysate at the same level as that induced by irradiation damage inhibited only the kinase activity associated with Cdk2. Cdc2 is likely to be inhibited by Thr-14/Tyr-15 phosphorylation after irradiation because Cdc2 was tyrosine-phosphorylated, and recombinant Cdc25 was able to increase its kinase activity significantly. Taken together, these results suggest that different CDKs are inhibited by different mechanisms following UV-induced DNA damage: Cdk2 is inhibited by the elevated level of p21; Cdk4 is inhibited by cooperation of p21 with other CDK inhibitors, like p27, and possibly by phosphorylation; and Cdc2 is inhibited by Thr-14/Tyr-15 phosphorylation. It is likely that these underlying mechanisms that inactivate CDKs are similar for other kinds of DNA damage.
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PMID:Cyclin-dependent kinases are inactivated by a combination of p21 and Thr-14/Tyr-15 phosphorylation after UV-induced DNA damage. 866 25

Cyclin-dependent protein kinases (Cdks) play a key role in the cell division cycle of eukaryotic cells. Cdc2, the first mammalian Cdk that was discovered, is expressed in S phase and functions in the G2 to M phase transition. By transfecting segments of the human cdc2 promoter linked to a reporter gene into monkey kidney (CV-1) cells, we identified the region containing the Sp1, E2F, and two CCAAT box binding sites as essential and sufficient for basal transcription. SV40 large T antigen (SV40-LT) is a viral oncoprotein that transactivates viral and cellular promoters and induces DNA synthesis in quiescent cells. SV40-LT transactivated wild-type cdc2 promoter/reporter constructs in a dose-dependent manner, coinciding with an increase in endogenous cdc2 mRNA. A mutant promoter from which the two CCAAT box motifs were deleted was 8-fold less sensitive to SV40-LT. Activation by SV40-LT did not require its ability to bind the retinoblastoma or p53 tumor suppressor proteins. SV40-LT induced a specific CCAAT box-binding factor (CBF) in CV-1 and COS-7 cells, as judged by gel shift and Southwestern analyses. Similar results were obtained in human fibroblasts expressing a conditional SV40-LT. The SV40-LT-inducible CBF appears to be novel and differs from the CBF that activates heat shock protein 70 gene expression.
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PMID:SV40 large T antigen transactivates the human cdc2 promoter by inducing a CCAAT box binding factor. 866 14

Previously we reported that neu differentiation factor (NDF)/heregulin (HRG) elevates tyrosine phosphorylation of its receptors erbB-3, erbB-4, and erbB-2 (through heterodimer formation). We also showed that both NDF/HRG and antibodies to erbB-2 can arrest growth and induce differentiation in breast cancer cells. In this study, we report on the mechanism of NDF/HRG-induced cellular effects. We show that NDF/HRG and antibodies to erbB-2 receptors up-regulate expression of p53 by stabilizing the protein. This is accompanied by up-regulation of the p53 inducible gene, p21CIP1/WAF1, in a variety of cell lines: MCF7 and their derivatives (MCF7/HER2, MN1 and MCF-7-puro), ZR75T and LnCap cells. The induction of p21 is further enhanced when cells are treated with both NDF/HRG and DNA-damaging chemotherapeutic agents (i.e. doxorubicin). The NDF/HRG mediated induction of p21 is dependent on wildtype p53, as it fails to occur in cells expressing dominant negative p53 (MDD2). Furthermore, p21 induction is capable of inactivating cdk2 complexes as measured by Histone H1 phosphorylation assays. Finally, we show that in primary cultures of breast and other cancers, p21 is significantly induced in response to NDF/HRG treatment. Collectively, these observations suggest that the mechanism of breast cancer cell growth inhibition and differentiation via erbB receptors activation is through a p53-mediated pathway.
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PMID:Neu differentiation factor (Heregulin) activates a p53-dependent pathway in cancer cells. 870 May 12

Deficiency in p53-mediated cell death is common in human cancer, contributing to both tumorigenesis and chemoresistance. In an attempt to restore p53, we evaluated in vitro infectivity and cytotoxicity of a wild type (w.t.) p53-expressing adenovirus (Ad-p53) toward a panel of human cancer cell lines (n = 19). At a multiplicity of infection of 30, both Ad-p53 and adenovirus expressing beta-galactosidase (Ad-LacZ) infected greater than 99% of cells derived from brain, lung, breast, ovarian, colon, and prostate cancer, but failed to infect leukemia or lymphoma cells. Ad-p53, but not Ad-LacZ, infection of cancer cells was followed by nuclear accumulation of the CDK inhibitor p21WAFI/CIPI, cell cycle arrest and loss of viability. Ad-p53 induced apoptotic death in cancer cells that express mutant p53, including multi-drug resistant cells, but fewer deaths were observed in some w.t. p53 expressing cells. Ad-p53-infected SKBr3 breast cancer cells were more sensitive to cytotoxicity of the DNA damaging drugs mitomycin C or Adriamycin, but not the M-phase specific drug vincristine. Our results suggest that Ad-p53 is capable of infecting and killing cancer cells of diverse tissue origins (including multi-drug resistant cancer cells), that p21WAFI/CIPI may be a useful marker of p53 infectivity and that there may be synergy between Ad-p53 and either mitomycin C or Adriamycin induced cell death in tumors with p53 mutations.
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PMID:In vitro evaluation of a p53-expressing adenovirus as an anti-cancer drug. 870 13

The c-Abl protein tyrosine kinase is activated by certain DNA-damaging agents, and its overexpression causes arrest in the G1 phase of the cell cycle by a mechanism dependent on the tumour-suppressor protein p53 (refs 2-4). Here we investigate the possible role of c-Abl in growth arrest induced by DNA damage. Transient transfection experiments using wild-type or inactivated c-Abl show that both induce expression of p21, an effector of p53, but only wild-type c-Abl downregulates the activity of the cyclin-dependent kinase Cdk2 and causes growth arrest. Exposure to ionizing radiation of cells that stably express active or inactive c-Abl is associated with induction of c-Abl/p53 complexes and p21 expression. However, cells expressing the dominant-negative c-Abl mutant and cells lacking the c-abl gene are impaired in their ability to downregulate Cdk2 or undergo G1 arrest in response to ionizing radiation. We also show that expression of c-Abl kinase in p21(-1-), but not in p53(-1-), cells results in downregulation of Cdk2. Our results suggest that c-Abl kinase contributes to the regulation of growth arrest induced by ionizing radiation by a p53-dependent, p21-independent mechanism.
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PMID:Role for c-Abl tyrosine kinase in growth arrest response to DNA damage. 871 45


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