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)

The level of various G1 cyclins and cyclin-dependent kinases (cdks) present in the nuclei of synchronized ML-1 human myeloblastic leukemia cells was determined as a function of time after initiation of cell growth with insulin-like growth factor-1 (IGF-1) and transferrin (Tf), and following induction of differentiation with transforming growth factor-beta1 (TGF-beta1). Cyclin E and cdk2 were expressed at relatively high levels in the nuclei of proliferation-stimulated cells, whereas cyclin D1 and cdk5 were expressed at comparably high levels in the nuclei of differentiation-induced cells. In the nuclear extracts from proliferation-stimulated cells, cyclin E complexed specifically with cdk2, whereas in nuclear extracts from differentiation-induced cells, cyclin D1 bound specifically to cdk5. Increased cyclin E/cdk2 expression was accompanied by increased DNA synthesis, whereas increased cyclin D1/cdk5 levels correlated with decreased DNA synthesis. In both growth- and differentiation-induced cells, cyclin D2 expression preceded the expression of cyclin D3, and a significantly larger amount of these cyclins was present in differentiation- as compared to proliferation-induced cells. In contrast, cdk4 and cdk6 were present at similar levels in the nuclear extracts from both growth- and differentiation-induced cells. These data show that, in ML-1 cells, the proliferation-associated progression from G1 to S, as well as the differentiation-associated transit from G1 to maturation is accompanied by the expression of specific cyclin/cdk pairs, comprising cdk2/cyclin E in growth and cdk5/cyclin D1 in differentiation.
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PMID:Differential expression of proteins regulating cell cycle progression in growth vs. differentiation. 915 Feb 73

We previously described in the CCL39 hamster fibroblast cell line the inhibition of DNA synthesis reinitiation by agents that elevate cyclic AMP. Here, we show that 8Br-cAMP strongly blocks both the growth factor-induced increase in cyclin D1 protein expression and decrease in p27(KIP1) protein levels, leaving untouched the levels of cyclin D3, cdk2 and cdk4. To assess the role of cyclin D1 in the cAMP-mediated inhibition of DNA synthesis, we overexpressed the cyclin D1 gene in CCL39 and analysed the cAMP response in stable transfectants. We showed that the kinase activities associated to G1 cyclin-cdk complexes are significantly more resistant to cAMP in cyclin D1 transfectants than in their normal counterparts, although the serum-induced p27(KIP1) disparition is still cAMP sensitive in cyclin D1 overexpressors. Interestingly, the mitogen-induced DNA synthesis reinitiation is also much less inhibited by cAMP in cyclin D1 transfectants than in control cells. These data clearly establish that the cAMP-inducible blockade of the G1 phase of the cell cycle can be partially alleviated by overexpression of cyclin D1 in hamster fibroblasts, thus strongly suggesting that cyclin D1 protein is one of the major targets for cAMP inhibitory action in fibroblasts.
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PMID:Cyclin D1 expression is a major target of the cAMP-induced inhibition of cell cycle entry in fibroblasts. 915 Mar 65

To elucidate the roles of cyclin-dependent kinase 6 (cdk6) in T cells, we examined its intracellular localization, kinase activity, and associated proteins in the Jurkat T lymphoblastoid cell line. Jurkat cells had a high level of cdk6, which was associated with cyclin D3, but not cyclin D2, the member of the cyclin D family. When stimulated by a combination of PHA and anti-CD28 mAb, cdk6 activity was up-regulated, as measured by an in vitro kinase assay using recombinant, truncated retinoblastoma tumor suppressor gene protein (Rb protein) as substrate. Activation was most prominent when cells were stimulated with the combination of PHA and anti-CD28, although significant increases were detected after stimulation with PHA alone. The combination also resulted in maximal activation of c-Jun kinase and IL-2 production. Costimulation resulted in a rapid translocation of cdk6 to the nucleus, as demonstrated by both confocal immunofluorescence microscopy and biochemical fractionation techniques. Cdk6 activation and nuclear translocation were also observed after stimulation of Jurkat cells using the anti-CD28 Ab in combination with a mAb to CD3 (OKT3). Furthermore, nuclear translocation was observed in normal human T lymphocytes isolated from peripheral blood and stimulated in vitro with PHA. Two potential endogenous cdk6 substrates (with apparent molecular masses of 75-80 and 55-60 kDa), which were immunoprecipitated with cdk6 and phosphorylated in the in vitro kinase assay, were also identified. These data demonstrate the rapid activation and intracellular translocation of cdk6, implicating this kinase in early signal transduction events in T cells.
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PMID:Rapid nuclear translocation and increased activity of cyclin-dependent kinase 6 after T cell activation. 916 30

In the present work we studied mechanisms of growth control in contact-inhibited and serum-deprived human diploid fibroblasts. The observation that the effects on [3H]thymidine incorporation and reduction of retinoblastoma gene product-phosphorylation were additive when contact-inhibition and serum-deprivation were combined led us to the conclusion that the underlying mechanisms might be different. Both contact-inhibition and serum-deprivation led to a strong decrease of cdk4-kinase-activity and cdk2-phosphorylation at Thr 160, while the total amounts of cdk4 and cdk2 remained constant. In contact-inhibited cells, we revealed a strong protein accumulation of the cdk2-inhibitor p27 and a slight, but significant increase of the cdk4-inhibitor p16. In serum-deprived cells, the protein levels in p27 and p16 remained low. In contrast, we detected a rapid decrease of cyclin D1 and cyclin D3 which did not occur in contact-inhibited cells. These results indicate that serum-deprivation and contact-inhibition have different mechanisms although they affect the same pathway cyclin D-cdk4, pRB, cyclin E-cdk2.
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PMID:Differences in the mechanisms of growth control in contact-inhibited and serum-deprived human fibroblasts. 940 Oct 1

Myxoid and round cell liposarcoma represents a morphological spectrum in which tumor progression from low-grade myxoid to high-grade round cell areas is frequently observed. A distinctive t(12;16)(q13;p11) reciprocal translocation rearranges the CHOP gene localized to 12q13 in most cases. Data concerning the occurrence of cell cycle aberrations in this subset of mesenchymal malignancies are very limited. Therefore, we analyzed a histologically homogeneous series of 21 cases of myxoid and round cell liposarcoma. The p53 pathway was studied by investigating the TP53 gene and protein, mdm2 protein, and p21Waf1 protein. The Rb-cyclin D pathway was analyzed by studying the pRb protein, the p16MTS1 gene, cyclin D1, cyclin D3, p27Kip1, cdk4, and cdk6 proteins. In contrast with the rare involvement of the TP53 gene in well differentiated liposarcoma, aberrations of the TP53 gene were observed in approximately 30% of cases of myxoid and round cell liposarcoma. Notably, mdm2 overexpression was seen in 56% of cases and correlated with histological grade, therefore indicating a possible role in tumor progression. Abnormalities involving the Rb-cyclin D pathway were observed in more than 90% of cases. pRb loss was present in one-third of cases and, at variance with that observed in other subsets of sarcoma, overexpression of cyclin Ds represented a rare event. Interestingly, upregulation of either cdk4 or cdk6 was demonstrated in 85% of cases.
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PMID:Molecular aberrations of the G1-S checkpoint in myxoid and round cell liposarcoma. 940 3

Tyr-Phe and Met limitation in vitro inhibited cell proliferation and proliferating cell nuclear antigen (PCNA) expression to a greater extent than serum limitation. Tyr-Phe and serum limitation arrested cells in the G0/G1 phase; Met limitation blocked cells in the G0/G1 and S phases. Tyr-Phe limitation progressively decreased cyclin D1 expression to 30% of control within four days and did not affect expression of cyclin D3 or cyclin-dependent kinase (CDK2, CDK4, and CDK5) expression, Met limitation decreased cyclin D3 expression to 25% of control and CDK2 expression to 32% of control by Day 4 and did not affect expression of cyclin D1, CDK4, and CDK5. Serum limitation inhibited cyclin D1 and cyclin D3 expression to 24% of control after four days and did not effect CDK expression. Expression of two CDK inhibitors, p21WAF1/Cip1 and p27Kip1, was not changed by amino acid or serum limitation. Dietary restriction of Tyr-Phe in mice bearing subcutaneous B16BL6 melanoma tumors decreased tumor growth rate compared with mice fed a normal diet. Tumors from Tyr-Phe-restricted mice exhibited decreased PCNA expression, G0/G1 phase cell cycle arrest, and reduced cyclin D1 expression. These data indicate that decreased tumor growth in vivo associated with dietary restriction of Tyr and Phe is cell cycle specific.
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PMID:Tyrosine and phenylalanine restriction induces G0/G1 cell cycle arrest in murine melanoma in vitro and in vivo. 942 72

In different systems, cyclic adenosine monophosphate (cAMP) either blocks or promotes cell cycle progression in mid to late G1 phase. Dog thyroid epithelial cells in primary culture constitute a model of positive control of DNA synthesis initiation and G0-S prereplicative phase progression by cAMP as a second messenger for thyrotropin (TSH). The cAMP-dependent mitogenic pathway is unique as it is independent of mitogen-activated protein kinase activation and differs from growth factor-dependent pathways at the level of the expression of several protooncogenes/transcription factors. This study examined the involvement of D-type G1 cyclins and their associated cyclin-dependent kinase (cdk4) in the cAMP-dependent G1 phase progression of dog thyroid cells. Unlike epidermal growth factor (EGF)+serum and other cAMP-independent mitogens, TSH did not induce the accumulation of cyclins D1 and D2 and partially inhibited the basal expression of the most abundant cyclin D3. However, TSH stimulation enhanced the nuclear detection of cyclin D3. This effect correlated with G1 and S phase progression. It was found to reflect both the unmasking of an epitope of cyclin D3 close to its domain of interaction with cdk4, and the nuclear translocation of cyclin D3. TSH and EGF+serum also induced a previously undescribed nuclear translocation of cdk4, the assembly of precipitable cyclin D3-cdk4 complexes, and the Rb kinase activity of these complexes. Previously, cdk4 activity was found to be required in the cAMP-dependent mitogenic pathway of dog thyrocytes, as in growth factor pathways. Here, microinjections of a cyclin D3 antibody showed that cyclin D3 is essential in the TSH/ cAMP-dependent mitogenesis, but not in the pathway of growth factors that induce cyclins D1 and D2. The present study (a) provides the first example in a normal cell of a stimulation of G1 phase progression occurring independently of an enhanced accumulation of cyclins D, (b) identifies the activation of cyclin D3 and cdk4 through their enhanced assembly and/or nuclear translocation, as first convergence steps of the parallel cAMP-dependent and growth factor mitogenic pathways, and (c) strongly suggests that this new mechanism is essential in the cAMP-dependent mitogenesis, which provides the first direct demonstration of the requirement for cyclin D3 in a G1 phase progression.
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PMID:A requirement for cyclin D3-cyclin-dependent kinase (cdk)-4 assembly in the cyclic adenosine monophosphate-dependent proliferation of thyrocytes. 950 75

The steroid hormone progesterone regulates proliferation and differentiation in the mammary gland and uterus by cell cycle phase-specific actions. In breast cancer cells the predominant effect of synthetic progestins is long-term growth inhibition and arrest in G1 phase. Progestin-mediated growth arrest of T-47D breast cancer cells was preceded by inhibition of cyclin D1-Cdk4, cyclin D3-Cdk4, and cyclin E-Cdk2 kinase activities in vitro and reduced phosphorylation of pRB and p107. This was accompanied by decreases in the expression of cyclins D1, D3, and E, decreased abundance of cyclin D1- and cyclin D3-Cdk4 complexes, increased association of the cyclin-dependent kinase (CDK) inhibitor p27 with the remaining Cdk4 complexes, and changes in the molecular masses and compositions of cyclin E complexes. In control cells cyclin E eluted from Superdex 200 as two peaks of approximately 120 and approximately 200 kDa, with the 120-kDa peak displaying greater cyclin E-associated kinase activity. Following progestin treatment, almost all of the cyclin E was in the 200-kDa, low-activity form, which was associated with the CDK inhibitors p21 and p27; this change preceded the inhibition of cell cycle progression. These data suggest preferential formation of this higher-molecular-weight, CDK inhibitor-bound form and a reduced number of cyclin E-Cdk2 complexes as mechanisms for the decreased cyclin E-associated kinase activity following progestin treatment. Ectopic expression of cyclin D1 in progestin-inhibited cells led to the reappearance of the 120-kDa active form of cyclin E-Cdk2 preceding the resumption of cell cycle progression. Thus, decreased cyclin expression and consequent increased CDK inhibitor association are likely to mediate the decreases in CDK activity accompanying progestin-mediated growth inhibition.
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PMID:Mechanisms of cyclin-dependent kinase inactivation by progestins. 952 53

Recent methodological developments allow expression measurement of many genes simultaneously, thereby revealing patterns of gene expression that can be related to phenotype. We hypothesized that through the use of such methods we could identify patterns of gene expression associated with the malignant phenotype in human bronchial epithelial cells (BEC). To test this hypothesis, a recently developed quantitative reverse transcriptase polymerase chain reaction method was used to assess simultaneously expression of 15 genes mechanistically associated with cell-cycle control (c-myc, E2F-1, p21, rb, PCNA, cyclin D2, cyclin D3, cyclin E, cdc2, CDK2, CDK4, mad, max p21, max p22, and p53) in normal cell cultures from five individuals and in nine different malignant BEC lines. Relative to the mean expression levels in cultured normal cell populations, expression of c-myc, E2F-1, PCNA, cyclin E, and CDK4 messenger RNA (mRNA) were significantly increased and expression of p21 and p53 mRNA were significantly decreased in one or two, but not all three subtypes (squamous, adenocarcinoma and small cell) of carcinoma cell lines evaluated. No single cell-cycle control gene discriminated all three subtypes from normal cell populations. In contrast, the gene expression index c-myc x E2F-1/p21 separated all carcinoma cell lines from all normal cell populations initially evaluated. This malignancy index was validated in an additional three cultured normal BEC and three carcinoma cell lines, as well as three pairs of matched primary normal bronchial epithelial and primary bronchogenic carcinoma samples, and three pairs of matched primary normal lung parenchyma and primary bronchogenic carcinoma tissue. Again, the c-myc x E2F-1/ p21 index successfully discriminated all cultured and primary normal from malignant samples and thereby had a predictive value of 1 (no false positives and no false negatives). We hypothesize that because of functional mutations in cell-cycle regulatory genes (e.g., p53 and/or rb), cells lose the ability to maintain a pattern of gene expression mechanistically associated with normal, division-limited homeostatic equilibrium. Because the c-myc x E2F-1/p21 gene expression index has high specificity for malignant tissue, it will allow confirmation that there is a significant amount of tumor tissue present in small (e.g., fine-needle) biopsy specimens prior to evaluating them for expression of other genes, such as those involved in chemoresistance or radioresistance. In addition, the goal of most gene therapy efforts is to alter levels of gene expression quantitatively. This index and others derived in a similar manner may better define potential gene therapy targets as well as response of targeted genes to therapy.
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PMID:The gene expression index c-myc x E2F-1/p21 is highly predictive of malignant phenotype in human bronchial epithelial cells. 965 Nov 76

To explore the regulation and function of D-type cyclins in breast cancer cells, the mouse mammary hyperplastic epithelial cell line TM2H was treated with 5 mM hexamethylenebisacetamide (HMBA), a polar differentiation factor. The resulting growth-inhibitory effect of HMBA was completely reversible and was analyzed in terms of percent cells in G1; association of D-type cyclins with cyclin-dependent kinase (cdk) 4 and cdk6; G1 kinase activity; association of retinoblastoma protein (pRb) and phosphorylated pRb with D-type cyclins; and association of p16INK4a, p15INK4b, and p27Kip1 with cdk4 and cdk6. Synchronized TM2H cells were examined at 0, 3, 5, 9, 12, and 24 h after exposure to 5 mM HMBA. Inhibition of DNA synthesis, as measured by thymidine uptake, was first observed at 5 h (40%) and peaked at 24 h (80%). Flow cytometry at 9 h showed treated cells to be in G1 arrest. Western blot analysis showed weakly detectable cyclin D1 but readily detectable cyclin D2 and D3 proteins at 0 h; thereafter, cyclin D2 and D3 protein levels remained higher while cyclin D1 levels declined significantly in treated versus untreated cells. By 5 h (early G1), HMBA had markedly inhibited cdk4 and cdk6 kinase activity (67% and 75%, respectively) in treated versus untreated cells. By 9 and 12 h, pRb levels had increased 3.4-fold in treated versus untreated cells. At 5 h, cyclin D-associated pRb was totally hypophosphorylated in treated cells and hyperphosphorylated in untreated cells. The levels of pRb associated with cyclin D2 and D3 increased 2.89-fold and 4.6-fold, respectively, in treated versus untreated cells. At 5 h, treated cells showed a fivefold increase in cdk4-associated p27Kip1 and, at 9 h, a fourfold increase in cdk6-associated p27Kip1 over control levels. In confirmation of these data, HMBA was found to inhibit the growth of Rb-positive Du/145Rb cells but not their Rb-negative parental Du/145 cells. The data suggest that HMBA-induced growth inhibition is due to multifactorial mechanisms involving decreases in total cyclin D1 and inhibition of cdk4 and cdk6 kinase activities through elevation of levels of cdk4- and cdk6-associated p27Kip1 and concomitant increases in hypophosphorylated pRb and stable cyclin D2/pRb and cyclin D3/pRb complexes that help maintain pRb in a functional state.
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PMID:Interaction of retinoblastoma protein and D cyclins during cell-growth inhibition by hexamethylenebisacetamide in TM2H mouse epithelial cells. 965 57


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