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)

We identified a novel human nucleolar phosphoprotein p130 (130 kDa) using a strategy for selecting monoclonal antibodies against nuclear proteins which oscillate in the cell cycle. p130 is localized in interphase nucleoli in a dotted manner. Complete extraction of p130 required a high concentration of salt (0.5 M NaCl) indicating that it binds firmly to the nucleolar components via ionic interaction. p130 is heavily phosphorylated, since alkaline phosphatase treatment converted the purified p130 into a 95 kDa product; this was further supported by the in vitro demonstration that cellular phosphatase and casein kinase II activities were responsible for the interchange of these two forms. Extracts of mitotic cells had lower concentrations of p130 compared to those of interphase cells suggesting that a proportion of p130 might be degraded during mitosis. Moreover, all the remaining p130 in mitotic cells was further phosphorylated, likely by a cdc2 kinase, resulting in increase in its solubility, and its dispersion throughout the entire cytoplasm. Thus, p130 in metaphase and anaphase cells was unable to be detected by immunofluorescence microscopy. At telophase, p130 reappeared and aggregated into a granular structure, resembling the prenucleolar bodies. These granules migrated from the nucleoplasm to the nucleoli in early G1-phase. Actinomycin D was able to induce segregation of p130-containing granules into the nucleoplasm, similar to the well-known behavior of the fibrillarin-containing granules, indicating that p130 is localized in the dense fibrillar component, a subnucleolar region for pre-rRNA synthesis and processing. The cDNA sequence of p130 revealed a remarkable feature, that a serine-rich stretch interspersed with acidic residues is repeated ten times. Such a characteristic is shared with a rat nucleolar phosphoprotein Nopp140, which is thought to shuttle between the nucleolus and the cytoplasm. Although p130 shows 74% identity to Nopp140, our observations suggest that during mitosis the functions of p130 are related to nucleologenesis.
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PMID:Cell-cycle-dependent alterations of a highly phosphorylated nucleolar protein p130 are associated with nucleologenesis. 765 14

The CDK-inhibitor p21WAF1/CIP1 has been implicated as a growth arrest mediator in p53-tumour suppression, cellular senescence and terminal differentiation. Cell type specific differences in p53-independent p21 expression and cell cycle arrest were found following treatment of human tumour cell lines with serum, 12-O-tetradecanoyl-phorbol-13-acetate (TPA), or okadaic acid (OA). TPA induced p21 in ML1, K562 and HL60 leukemia cells, whereas OA induced p21 in SW480 and GM4723 carcinoma cells as well as in leukemic cells. In addition, TPA- and serum- but not OA-induced cell cycle arrest was reversed upon return of p21 to basal levels. To further investigate the mechanisms underlying p53-independent regulation of p21, the transcription inhibitor, Actinomycin D (AMD), was used to block p21 expression. The results showed a complete inhibition of p21 mRNA and protein induction by TPA or adriamycin but little effect on p21 mRNA induced by OA in the presence of AMD. These results suggested that TPA-induced p21 expression requires transcription initiation, while a post-transcriptional mechanism may be involved in OA-induction as well. Transient transfection assays with p21 promoter-luciferase reporters and TPA or OA treatment further confirmed that TPA, and to a lesser extent, OA, initiated transcription of p21. Finally, the protein kinase C inhibitor, staurosporine, was found to interfere with p21 induction and prevent cell cycle arrest following treatment with TPA but not OA, suggesting a requirement for PKC in TPA activation of p21 expression.
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PMID:Regulation of p21WAF1/CIP1 expression by p53-independent pathways. 862 72

The TRAIL death receptor KILLER/DR5 is induced by DNA damaging agents in wild-type p53-expressing cells. Here we show that, unlike the p53-target CDK-inhibitor p21WAF1/CIP1, the TRAIL death receptor KILLER/DR5 is only induced in cells undergoing p53-dependent apoptosis and not cell cycle arrest. Thus GM glioblastoma cells carrying an inducible MMTV-driven p53 gene undergo cell cycle arrest and upregulate p21 but not KILLER/DR5 expression upon dexamethasone exposure. WI38 normal lung fibroblasts undergoing cell cycle arrest in response to ionizing irradiation also induce p21 but not KILLER/DR5 gene expression. KILLER/DR5 upregulation is also deficient in irradiated lymphoblastoid cells derived from patients with Ataxia Teleangiectasia suggesting a role for the ATM-p53 pathway in regulating KILLER/DR5 expression after DNA damage. Inhibition of transcription by Actinomycin D blocks both KILLER/DR5 and p21 induction in cells undergoing p53-dependent apoptosis. Our results suggest that the p53-dependent transcriptional induction of KILLER/DR5 death receptor is restricted to cells undergoing apoptosis and not cells undergoing exclusively p53-dependent G1 arrest.
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PMID:Induction of the TRAIL receptor KILLER/DR5 in p53-dependent apoptosis but not growth arrest. 1059 42

HPV-immortalized human oral keratinocytes can convert to tumorigenic cells by chemical carcinogens while normal human keratinocytes cannot. The different responses of these cells to chemical carcinogens may be due to their different genomic stability. Since the genomic stability of cells is closely associated with cell cycle control, we correlated cell cycle progression with the cellular levels or activities of key G(1) phase cell cycle regulatory proteins, p21(WAF/CIP1), cyclins (A, D1 and E), cdks (cdk2 and cdk4), gadd45 and PCNA proteins in normal and HPV-immortalized oral keratinocytes before and after treatment with a genotoxic agent, actinomycin D. Actinomycin D treatment in normal cells cause (i) an inhibition in the activity of cdk2 kinase, (ii) an increase in the level of WAF1/CIP1 mRNA and p21(WAF1/CIP1), (iii) an increase in the binding of the p21(WAF1/CIP1) protein with the cdk2 protein, (iv) a reduction in the transcription of cyclin A messages, (v) an increase in the p53 inducible gadd45 protein, and (vi) a significant decrease in the synthesis and level of the DNA replication protein, PCNA. However, actinomycin D failed to induce these changes in the HPV-immortalized cells. These results are consistent with the hypothesis that in HPV-immortalized oral keratinocytes, the key cell cycle regulatory components of the G(1) phase are significantly altered thereby making them prone to mutagenic damage when exposed to DNA damaging agents.
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PMID:Role of HPV in tumorigenesis of oral keratinocytes. 2154 26

Cdc25C is a cell cycle protein of the dual specificity phosphatase family essential for activating the cdk1/Cyclin B1 complex in cells entering into mitosis. Since altered cell cycle is a hallmark of human cancers, we investigated androgen regulation of Cdc25C protein in human prostate cancer (PCa) cells, including androgen-sensitive (AS) LNCaP C-33 cells and androgen-independent (AI) LNCaP C-81 as well as PC-3 cells. In the regular culture condition containing fetal bovine serum (FBS), Cdc25C protein levels were similar in these PCa cells. In a steroid-reduced condition, Cdc25C protein was greatly decreased in AS C-33 cells but not AI C-81 or PC-3 cells. In androgen-treated C-33 cells, the Cdc25C protein level was greatly elevated, following a dose- and a time-dependent manner, correlating with increased cell proliferation. This androgen effect was blocked by Casodex, an androgen receptor blocker. Nevertheless, epidermal growth factor (EGF), a growth stimulator of PCa cells, could only increase Cdc25C protein level by about 1.5-fold. Altered expression of Cdc25C in C-33 cells and PC-3 cells by cDNA and/or shRNA transfection is associated with the corresponding changes of cell growth and Cyclin B1 protein level. Actinomycin D and cycloheximide could only partially block androgen-induced Cdc25C protein level. Treatments with both proteasomal and lysosomal inhibitors resulted in elevated Cdc25C protein levels. Immunoprecipitation revealed that androgens reduced the ubiquitination of Cdc25C proteins. These results show for the first time that Cdc25C protein plays a role in regulating PCa cell growth, and androgen treatments, but not EGF, greatly increase Cdc25C protein levels in AS PCa cells, which is in part by decreasing its degradation. These results can lead to advanced PCa therapy via up-regulating the degradation pathways of Cdc25C protein.
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PMID:Androgens upregulate Cdc25C protein by inhibiting its proteasomal and lysosomal degradation pathways. 2363 32