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)

In a screen of mouse erythroleukemia cDNA expression libraries with anti-phosphotyrosine antibodies, designed to isolate tyrosine kinase coding sequences, we identified several cDNAs encoding proteins identical or very similar to known protein-tyrosine kinases. However, two frequently isolated cDNAs, clk and nek, encode proteins which are most closely related to protein kinases involved in regulating progression through the cell cycle, and contain motifs generally considered diagnostic of protein-serine/threonine kinases. The clk gene product contains a C-terminal cdc2-like kinase domain, most similar to the FUS3 catalytic domain. The Clk protein, expressed in bacteria, becomes efficiently phosphorylated in vitro on tyrosine as well as serine/threonine, and phosphorylates the exogenous substrate poly(glu, tyr) on tyrosine. Direct biochemical evidence indicates that both protein-tyrosine and protein-serine/threonine kinase activities are intrinsic to the Clk catalytic domain. These results suggest the existence of a novel class of protein kinases, with an unusual substrate specificity, which may be involved in cell cycle control.
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PMID:A mammalian protein kinase with potential for serine/threonine and tyrosine phosphorylation is related to cell cycle regulators. 182 55

Cell division cycle mutants defective in G1, DNA replication or nuclear division were tested for sporulation at semi-restrictive temperatures. In cdc1-7, cdc5-120, cdc17-L16 and cdc18-46 no abnormalities were observed; cdc10-129, cdc20-M10, cdc21-M6B, cdc23-M36 and cdc24-M38 formed four-spored asci but with a low efficiency; cdc22-M45 was completely defective in meiosis, but could conjugate and formed zygotes with a single nucleus. Mutants defective in the mitotic initiation genes cdc2, cdc25 and cdc13 were blocked in meiosis II. None of the wee1-50, adh.nim1+ and win1+ alleles had any affect on sporulation, suggesting that their interactions with cdc25 and cdc2 are specific to mitosis. The meiotic function of cdc13 is TBZ-sensitive and probably exerted downstream of cdc2. Single mutants in cut1 or cut2 did not effect sporulation, whereas the double mutant cut1 cut2 formed two-spored asci. The results demonstrate that the cell division cycle and the meiotic developmental pathway share common genes and regulatory cascades.
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PMID:Common genes and pathways in the regulation of the mitotic and meiotic cell cycles of Schizosaccharomyces pombe. 193 26

Progression through the G1 phase of the cell cycle is regulated in part by the D-type cyclin-dependent kinases, cdk4 and cdk6. Genes encoding two specific inhibitors of these kinases, human p16(INK4a/MTS1) and p15(INK4b/MTS2), map to a region of common cytogenetic abnormalities on chromosome 9p21. The murine cognates of these genes were isolated and identified as mouse p16INK4a and p15INK4b based on their homology to their human counterparts and their selective transcriptional induction by SV40T-antigen and TGF-beta, respectively. Both genes map to position C3-C6 on mouse chromosome 4, in a region syntenic with human chromosome 9p. Amplification of polyadenylated mRNA by polymerase chain reactions revealed no expression of mouse p16INK4a in many normal tissues, whereas p15INK4b was expressed ubiquitously. Like human p16INK4a, mouse p16INK4a binds specifically to cdk4 and cdk6 in vitro and inhibits the phosphorylation of the retinoblastoma protein, pRb, by each of these cyclin D-dependent kinases. In mouse MEL erythroleukemia cells, p16INK4a associates preferentially with cdk6 under conditions where cdk4 and cdk6 are coexpressed at equivalent levels. Expression vectors encoding human or mouse p16INK4a caused G1 phase arrest in NIH3T3 fibroblasts, and cyclin D1- and cdk4-dependent pRb kinase activities were inhibited in the p16INK4a-arrested cells.
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PMID:Cloning and characterization of murine p16INK4a and p15INK4b genes. 765 26

Differentiation of murine erythroleukemia cells induced by hexamethylene bisacetamide (HMBA) is associated with accumulation of underphosphorylated retinoblastoma protein (pRB) and an increase in retinoblastoma (RB) gene expression. Here we show that HMBA causes a rapid decrease in the level of cyclin-dependent kinase 4 (cdk4) protein. This decrease results from decreased stability of the protein, while the rate of synthesis of the protein is not affected by HMBA. The decrease in the level of cdk4 protein is followed by suppression of the pRB kinase activity associated with cdk4. Cyclin D3, which can bind and activated cdk4, is increased in HMBA-induced cells and is found in complex with pRB and the transcription factor E2F. In uninduced cells cyclin D3 complexes with pRB and E2F are barely detected. At the later stages of differentiation, MEL cells become arrested in G1 and cdk2 kinase activity is suppressed; this is accompanied by a decrease in the level of cyclin A and cdk2 proteins. Cells transfected with cdk4, which continue to overexpress cdk4 protein during culture with HMBA, are resistant to HMBA-induced differentiation. In contrast, overexpression of cdk2 protein does not inhibit induced differentiation. These findings suggest that suppression of cdk4 is a critical event in the pathway leading to terminal differentiation of erythroleukemia cells.
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PMID:Suppression of cyclin-dependent kinase 4 during induced differentiation of erythroleukemia cells. 793 34

Transformed cells do not necessarily lose their capacity to differentiate. Various agents can induce many types of neoplastic cells to terminal differentiation. Among such inducers, a particularly potent group consists of hybrid polar compounds; hexamethylene bisacetamide (HMBA) is the prototype of this group. With virus-transformed murine erythroleukemia cells as a model, HMBA was shown to cause these cells to arrest in G1 phase and express globin genes. This review focuses on HMBA-induced modulation of factors regulating G1-to-S phase progression, including a decrease in the G1 cyclin-dependent kinase cdk4, associated with inhibition of phosphorylation of the retinoblastoma protein pRB and possibly other related proteins that, in turn, sequester factors required for initiation of DNA synthesis; this provides a possible mechanism for HMBA-induced terminal cell division. Evidence that hybrid polar compounds have therapeutic potential for cancer treatment will also be reviewed.
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PMID:Inducing differentiation of transformed cells with hybrid polar compounds: a cell cycle-dependent process. 793 35

Phosphoprotein p18 was identified originally on the basis of its very high level of expression in leukemic cells of different lineages. Changes in the level of p18 accumulation and phosphorylation associated with induction of differentiation of leukemic cells suggested a potential role for this phosphoprotein in cellular proliferation and differentiation and possibly in malignant transformation. Recent studies have demonstrated that p18 plays an important role in cell cycle progression by serving as a substrate for p34(cdc2) kinase. These studies showed that inhibition of p18 expression in leukemic cells results in growth retardation and accumulation of cells in G(2)-M. In this study, we explore the potential role of p18 in cellular transformation by investigating the effects of inhibition of p18 expression on the malignant phenotype of K562 erythroleukemia cells. These studies show that antisense inhibition of p18 expression in leukemic cells results in growth arrest at a lower saturation density, loss of serum independence, and loss of anchorage-independent growth in vitro. In addition, inhibition of p18 expression results in a marked inhibition of tumorigenicity of leukemic cells in vivo in the severe combined immune deficiency mouse model. These studies demonstrate that the high level of p18 expression in leukemic cells is necessary for the maintenance of the transformed phenotype and suggest p18 as a potential target for antileukemic interventions.
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PMID:Antisense RNA inhibition of phosphoprotein p18 expression abrogates the transformed phenotype of leukemic cells. 864 Aug 38

The pathways that regulate the S-phase events associated with the control of DNA replication are poorly understood. The bone marrow megakaryocytes are unique in that they leave the diploid (2C) state to differentiate, synthesizing 4 to 64 times the normal DNA content within a single nucleus, a process known as endomitosis. Human erythroleukemia (HEL) cells model this process, becoming polyploid during phorbol diester-induced megakaryocyte differentiation. The mitotic arrest occurring in these polyploid cells involves novel alterations in the cdk1/cyclin B1 complex: a marked reduction in cdk1 protein levels, and an elevated and sustained expression of cyclin B1. Endomitotic cells thus lack cdk1/cyclin B1-associated H1-histone kinase activity. Constitutive over-expression of cdk1 in endomitotic cells failed to re-initiate normal mitotic events even though cdk1 was present in a 10-fold excess. This was due to an inability of cyclin-B1 to physically associate with cdk1. Nonetheless, endomitotic cyclin B1 possesses immunoprecipitable H1-histone kinase activity, and specifically translocates to the nucleus. We conclude that mitosis is abrogated during endomitosis due to the absence of cdk1 and the failure to form M-phase promoting factor, resulting in a disassociation of mitosis from the completion of S-phase. Further studies on cyclin and its interacting proteins should be informative in understanding endomitosis and cell cycle control.
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PMID:Novel alterations in CDK1/cyclin B1 kinase complex formation occur during the acquisition of a polyploid DNA content. 868 53

Considerable progress has been made toward elucidating the pathway of induction of terminal differentiation of transformed cells by hybrid polar compounds such as hexamethylene bisacetamide (HMBA). HMBA alters factors controlling G1-to-S phase transition, leading to G1 arrest and inhibition of DNA synthesis. Among the inducer-mediated changes, suppression of cyclin-dependent kinase cdk4, which may be required for phosphorylation of the retinoblastoma protein pRB and perhaps p107, is critical in the pathway of terminal differentiation. HMBA induces an increase in the level of p21 which inhibits cyclin-dependent kinase activity and, in turn, may cause cells to arrest in G1. p107 complexes with transcription factor E2F, which may alter E2F-dependent gene transcription. the relationship of the inducer-mediated changes in cyclins, cdks, cyclin-cdk inhibitors and transcription factors to the expression of differentiation-specific genes has not yet been established. The hybrid polar compounds are potent inducers of differentiation of a wide variety of transformed cells. HMBA has been shown to induce differentiation of neoplastic cells in patients. A second generation of hybrid polar compounds have been synthesized which are up to 1000 fold more potent than HMBA on a molar basis as inducers of murine erythroleukemia (MEL) cells and other transformed cells in vitro. The potential of these compounds as clinically useful inducers of differentiation of cancer cells is under study.
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PMID:Cell cycle regulatory proteins are targets for induced differentiation of transformed cells: Molecular and clinical studies employing hybrid polar compounds. 871 72

The cytodifferentiation agent hexamethylene bisacetamide (HMBA) is an inducer of differentiation of a variety of transformed cells, including the murine erythroleukemia (MEL) cell line. Induction of differentiation of MEL cells is a multistep process resulting in cessation of cell division and phenotypic maturation (including hemoglobin production). To investigate HMBA-induced MEL cell differentiation, we have analyzed the regulation of the E2F transcription factor. E2F regulates the transcription of several genes whose products are involved in both cell cycle regulation and differentiation. In nuclear extracts from uninduced MEL cells, three complexes were detected using gel mobility assays with the E2F/E2 oligonucleotide. The complex with the fastest mobility is the free form of E2F binding to DNA, and the more slowly migrating complexes contain E2F, p107, and cdk2. By 8 h of HMBA induction and for the remainder of the differentiation process, the free E2F complex is not detected, and only complexes of slower mobility, which contain p107 and cdk2, are found. The level of p107 protein increases during induction of differentiation; there is no change in the level of cdk2 protein and E2F-4 and DP-1 proteins during the first 4 days. The level of E2F-1 mRNA does not change, but a new form of E2F is detected during induction of differentiation. Thus, HMBA causes a selective loss in the free E2F DNA-binding complex, an increase in p107 protein, and an increase in a form of E2F protein during MEL cell differentiation.
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PMID:Changes in E2F DNA-binding activity during induced erythroid differentiation. 878 31

It is generally recognized that bcl-2 gene strongly protects cells from apoptosis in various situations. But its function is still to be examined. We analyzed the effect of bcl-2 gene using growth factor dependent cell line, TF-1, derived from an erythroleukemia patient. On GM-CSF removal TF-1 (bcl-2) cells which were transfected with bcl-2 cDNA by retrovirus vector system survived and arrested in G0-1 phase of the cell cycle, while TF-1 (mock) cells which were transfected with vector only also arrested in G0-1 but decreased in number in several days and showed typical apoptosis. N-acetylcysteine, one of antioxidants, did not show such anti-apoptotic effect as bcl-2 in the preincubation experiment. By centrifugal elutriation system the G0-1 arrested subfraction of TF-1 (bcl-2) showed time delay at the re-entry into cell after GM-CSF re-addition when compared with the G0-1 arrested subfraction of TF-1 (mock). Similar delay in cell cycle progression was observed after 24hs-exposure of staurosporine, a protein kinase C (PKC) inhibitor. The expression of cell cycle genes including cyclin A, C, D1, E, cdk2, 4, c-myc, bax and bcl-x showed no difference between these two cell lines upon growth factor removal. These results imply that the functional commitment of bcl-2 into cell cycle progression under the situation of apoptosis especially at the restriction point of G1-S transition.
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PMID:[Overexpression of bcl-2 suppresses apoptosis in the human leukemia cell line TF-1]. 925 8


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