Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.1 (protein kinase)
 81,284 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Irreversible exit from the cell cycle precludes the ability of cardiac muscle cells to increase cell number after infarction. Using adenoviral E1A, we previously demonstrated dual pocket protein- and p300-dependent pathways in neonatal rat cardiac myocytes, and have proven that E2F-1, which occupies the Rb pocket, suffices for these actions of E1A. By contrast, the susceptibility of adult ventricular cells to viral delivery of exogenous cell cycle regulators has not been tested, in vitro or in vivo. In cultured adult ventricular myocytes, adenoviral gene transfer of E2F-1 induced expression of proliferating cell nuclear antigen, cyclin-dependent protein kinase 4, cell division cycle 2 kinase, DNA synthesis, and apoptosis. In vivo, adenoviral delivery of E2F-1 by direct injection into myocardium induced DNA synthesis, shown by 5'-bromodeoxyuridine incorporation, and accumulation in G2/M, by image analysis of Feulgen-stained nuclei. In p53(-)/- mice, the prevalence of G1 exit was more than twofold greater; however, E2F-1 evoked apoptosis and rapid mortality comparably in both backgrounds. Thus, the differential effects of E2F-1 on G1 exit in wild-type versus p53-deficient mice illustrate the combinatorial power of viral gene delivery to genetically defined recipients: E2F-1 can override the G1/S checkpoint in postmitotic ventricular myocytes in vitro and in vivo, but leads to apoptosis even in p53(-)/- mice.
 ...
PMID:Adenoviral delivery of E2F-1 directs cell cycle reentry and p53-independent apoptosis in postmitotic adult myocardium in vivo. 938 35

In previous studies we observed that inhibition of cyclic 3',5'-nucleotide phosphodiesterase (PDE) isozymes, namely isozyme PDE3, suppresses proliferation of rat renal glomerular mesangial cells in vitro and in vivo. To determine whether activation of the cyclic adenosine monophosphate (cAMP)-protein kinase A (PKA) signaling pathway coupled to specific PDE isozymes modulates accelerated proliferation of renal epithelial cells, we investigated the effect of selective PDE isozyme inhibition on renal epithelial cell proliferation induced in rats by injection of folic acid (FA). In extracts from suspensions of renal cortical tubules, cAMP was metabolized predominantly by isozyme PDE4; activity of PDE3 was about three times lower. The increase in proliferative activity of renal cortical tissue from FA-injected rats, evaluated by immunostaining with Mib-1 antibody, was limited to tubular epithelial cells. Administration of the PDE3 inhibitors cilostazol or cilostamide together with the PDE4 inhibitor rolipram blocked mitogenic synthesis of DNA, as determined by (3H)-thymidine incorporation into renal cortical DNA, in FA-treated rats. FA injection caused an increase of more than 10-fold in proliferating cell nuclear antigen (PCNA) in renal cortical tissue; administration of the potent PDE3 inhibitor lixazinone or, to a lesser degree, cilostazol suppressed these high PCNA levels, whereas rolipram alone had no effect. The results indicate that FA-stimulated in vivo proliferation of renal tubular epithelial cells is down-regulated by activation of a cAMP-PKA signaling pathway linked to PDE3 isozymes. These observations are consistent with the notion that negative crosstalk between cAMP signaling and mitogen-stimulated signaling pathways regulates mitogenesis of renal cells of different terminal differentiation, including tubular epithelial cells.
 ...
PMID:Inhibitors of cyclic nucleotide phosphodiesterase isozymes block renal tubular cell proliferation induced by folic acid. 939 Jun 32

PKR (protein kinase, interferon-responsive) is a ribosomal-associated protein kinase found in all human cells. When activated by dsRNA or polyanionic substances, PKR efficiently inhibits cellular protein synthesis. PKR expression has been correlated with cellular differentiation in a number of tumor types, including squamous cell carcinoma of the head and neck region. Although transfection of PKR into mouse fibroblasts and yeast cells inhibits proliferation, it is not known if modulation of native PKR levels occurs during cellular proliferation and differentiation in human normal and neoplastic tissues. To determine whether PKR expression was inversely related to proliferative activity in vivo, we used double-label immunohistochemistry to colocalize PKR and the proliferation marker, proliferating cell nuclear antigen (PCNA), in a series of head and neck squamous cell carcinomas. Overall, neoplasms demonstrating high levels of PKR showed low levels of PCNA immunoreactivity; carcinomas with low levels of PKR expressed high levels of PCNA. Within individual tumors, PKR and PCNA showed an inverse regional distribution: PKR was located predominantly in the center of tumor nests, while PCNA was restricted to the periphery. Patients whose tumors expressed high levels of both PKR and PCNA had the longest mean disease-free survival. These findings support the hypothesis that PKR levels are modulated in cell proliferation and differentiation in head and neck squamous cell carcinoma. Further studies are needed to clarify the mechanisms underlying the antiproliferative activity of PKR.
 ...
PMID:Interferon-responsive protein kinase (p68) and proliferating cell nuclear antigen are inversely distributed in head and neck squamous cell carcinoma. 942 82

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.
 ...
PMID:Tyrosine and phenylalanine restriction induces G0/G1 cell cycle arrest in murine melanoma in vitro and in vivo. 942 72

Proper control of the mammalian cell cycle requires the function of cyclin-dependent kinase (CDK) inhibitors. The p21 family currently includes three distinct genes, p21, p27(Kip1), and p57(Kip2), that share a common N-terminal domain for binding to and inhibiting the kinase activity of CDK-cyclin complexes. The p21 protein also binds to proliferating cell nuclear antigen (PCNA) through a separate C-terminal domain affecting DNA replication and repair. The p27 and p57 proteins also each contain unique C-terminal domains whose functions are unknown. Here we show that the human p57 protein, like p21, contains a PCNA-binding domain within its C terminus that, when separated from its N-terminal CDK-cyclin binding domain, can prevent DNA replication in vitro and S phase entry in vivo. Disruption of either CDK/cyclin or PCNA binding partially reduced p57's ability to suppress myc/RAS-mediated transformation in primary cells, while loss of both inhibitory functions completely eliminated p57's suppressive activity. Thus, control of cell cycle and suppression of cell transformation by p57 require both CDK and PCNA inhibitory activity, and disruption of either or both functions may lead to uncontrolled cell growth.
 ...
PMID:Suppression of cell transformation by the cyclin-dependent kinase inhibitor p57KIP2 requires binding to proliferating cell nuclear antigen. 946 25

A unique feature of p21 that distinguishes it from the other cyclin-dependent kinase (CDK) inhibitors is its ability to associate with the proliferating cell nuclear antigen (PCNA), an auxiliary factor for DNA polymerases delta and epsilon. While it is now well established that inhibition of cyclin/CDK complexes by p21 can result in G1 cell cycle arrest, the consequences of p21/PCNA interaction on cell cycle progression have not yet been determined. Here, we show, using a tetracycline-regulated system, that expression of wild-type p21 in p53-deficient DLD1 human colon cancer cells inhibits DNA synthesis and causes G1 and G2 cell cycle arrest. Similar effects are observed in cells expressing p21CDK-, a mutant impaired in the interaction with CDKs, but not in cells expressing p21PCNA-, a mutant deficient for the interaction with PCNA. Analysis of cells treated with a p21-derived PCNA-binding peptide provides additional evidence that the growth inhibitory effects of p21 and p21CDK result from their ability to bind to PCNA. Our results suggest that p21 might inhibit cell cycle progression by two independent mechanisms, inhibition of cyclin/CDK complexes, and inhibition of PCNA function resulting in both G1 and G2 arrest.
 ...
PMID:p21 binding to PCNA causes G1 and G2 cell cycle arrest in p53-deficient cells. 946 56

p21waf1 has been shown to mediate the p53-dependent growth arrest induced by DNA-damaging agents. Several functions have been ascribed to p21waf1 that could be involved in this growth arrest. For one, p21waf1 is an efficient inhibitor of cyclin-dependent kinases (CDKs). Also, p21waf1 can interact with proliferating cell nuclear antigen (PCNA), and as such inhibit in vitro DNA-replication. Finally, p21waf1 has been reported to inhibit stress-activated protein kinases (SAPKs). In order to study these multiple functions of p21waf1 we have established U2OS-derived cell lines, in which the expression of p21waf1 can be regulated by the concentration of tetracycline in the culture medium. We observed a virtually complete, but reversible inhibition of cell growth upon induction of p21waf1-expression. Both [3H]thymidine-incorporation and CDK2-activity were strongly inhibited by p21waf1. Upon induction of p21waf1 cells accumulated with a 2N or 4N DNA content suggesting events in G1 and G2 can be inhibited by p21waf1. Indeed, kinase activity associated with cyclin B was reduced dramatically upon induction of p21waf1, although cyclin B continues to be expressed. In contrast, p21waf1 does not seem to inhibit the function of PCNA in ongoing DNA replication, since cells expressing high levels of p21waf1 apparently progressed normally through S-phase. Also, the activity of SAPKs was not substantially affected by the high levels of p21waf1. We conclude that, at least in these U2OS-derived cells, p21waf1 functions as an inhibitor of CDK-activity in G1 and G2, but not as an inhibitor of PCNA or SAPKs.
 ...
PMID:p21waf1 can block cells at two points in the cell cycle, but does not interfere with processive DNA-replication or stress-activated kinases. 948 32

In tissue culture systems, p21 and p27 inhibit cyclin-dependent kinase (CDK) activity and cell cycle progression in response to numerous stimuli, but little is known about their involvement in cell growth in vivo. We examined the modulation of CDK activity by these proteins after 70% partial hepatectomy (PH), an in vivo model of synchronous hepatocyte cell cycle progression. After PH in BALB/c mice, p21 was induced during the prereplicative (G1) phase and was maximally expressed after peak hepatocyte DNA synthesis. p27 was present in quiescent liver and was minimally induced after PH. p21 and p27 immunoprecipitated with CDK2, CDK4, and cyclin D1 in the regenerating liver. The activity of CDK2-, CDK4- and cyclin D1-associated kinases was upregulated after PH, and maximal activity of these enzyme complexes corresponded to peak DNA synthesis. Immunodepletion experiments suggested that p27 plays a role in downregulating CDK2 activity before and after peak DNA synthesis. Compared to cogenic wild-type mice, p21-/- mice demonstrated evidence of markedly accelerated hepatocyte progression through G1 phase after PH: DNA synthesis, upregulation of cyclin A and PCNA, induction of cyclin D1- and CDK2-associated kinase activity, and appearance of a phosphorylated retinoblastoma protein (Rb) species occurred earlier in the p21-/- mice. These results suggest that p21 and p27 modulate CDK activity in the regenerating liver, and that p21 regulates the rate of progression through G1 phase of the cell cycle in vivo.
 ...
PMID:Involvement of p21 and p27 in the regulation of CDK activity and cell cycle progression in the regenerating liver. 957 95

The cyclin-dependent kinase inhibitor p21(WAF1/CIP1/SDI1/CAP20) exists in normal human fibroblasts in a quaternary complex with a cyclin, a cyclin-dependent kinase, and proliferating cell nuclear antigen. A model was proposed in which, during p53-mediated suppression of cell proliferation following treatment with 254 nm UV radiation (UVC), the enhanced expression of p21 might inhibit DNA replication by virtue of its interactions with proliferating cell nuclear antigen. To test this model, we examined the mechanisms of inhibition of DNA replication in diploid human fibroblasts that express human papillomavirus type 16 E6, which inactivates p53. E6-expressing cells were defective in G1 checkpoint responses of induction of p21 and G1 arrest after ionizing radiation-induced damage to DNA. Accordingly, E6-expressing cells were resistant to inactivation of single-cell colony formation by ionizing radiation. E6 cells also displayed normal S-phase checkpoint responses of inhibition and recovery of replicon initiation following exposure to ionizing radiation and normal ability to bypass pyrimidine dimers during DNA replication soon after UVC irradiation (i.e., postreplication repair). However, DNA replication 6 h after UVC exposure was significantly inhibited in E6 cells in comparison to isogenic controls. This failure to maintain DNA replication in S-phase cells was associated with enhanced sensitivity to inactivation of single-cell colony formation by UVC. These results indicate that the p53-induced p21 pathway is not involved in the immediate S-phase responses to radiation-induced DNA damage of inhibition of replicon initiation and translesion bypass. However, our results demonstrate that p53 and, conceivably, p21 contribute to the ability of normal human fibroblasts to sustain DNA replication activity and form colonies following UVC irradiation.
 ...
PMID:p53-dependent signaling sustains DNA replication and enhances clonogenic survival in 254 nm ultraviolet-irradiated human fibroblasts. 958 44

The p21 protein, a cyclin-dependent kinase (CDK) inhibitor, is capable of binding to both cyclin-CDK and the proliferating cell nuclear antigen (PCNA). Through its binding to PCNA, p21 can regulate the function of PCNA differentially in replication and repair. To gain an understanding of the precise mechanism by which p21 affects PCNA function, we have designed a new assay for replication factor C (RFC)-catalyzed loading of PCNA onto DNA, a method that utilizes a primer-template DNA attached to agarose beads via biotin-streptavidin. Using this assay, we showed that RFC remains transiently associated with PCNA on the DNA after the loading reaction. Addition of p21 did not inhibit RFC-dependent PCNA loading; rather, p21 formed a stable complex with PCNA on the DNA. In contrast, the formation of a p21-PCNA complex on the DNA resulted in the displacement of RFC from the DNA. The nonhydrolyzable analogs of ATP, adenosine-5'-O-(3-thiotriphosphate) (ATPgammaS) and adenyl-imidodiphosphate, each stabilized the primer recognition complex containing RFC and PCNA in the absence of p21. RFC in the ATPgammaS-activated complex was no longer displaced from the DNA by p21. We propose that p21 stimulates the dissociation of the RFC from the PCNA-DNA complex in a process that requires ATP hydrolysis and then inhibits subsequent PCNA-dependent events in DNA replication. The data suggest that the conformation of RFC in the primer recognition complex might change on hydrolysis of ATP. We also suggest that the p21-PCNA complex that remains attached to DNA might function to tether cyclin-CDK complexes to specific regions of the genome.
 ...
PMID:Cyclin-dependent kinase inhibitor p21 modulates the DNA primer-template recognition complex. 963 2


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>