Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P04637 (p53)
 77,613 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The cdk2 gene has been identified as a human cdc2/CDC28-related gene that encodes a protein kinase essential for the G1/S transition in mammalian cells, but not for the G2/M transition, which requires Cdk1, another p34cdc2/CDC28 homolog. Novel potential functions of Cdk2 have been uncovered by using two potent and specific inhibitors of its kinase activity, roscovitine and olomoucine, on human wt p53-expresser untransformed and tumor-derived cells. At concentrations equal or superior to respectively 30- and 20-fold their in vitro IC50 values for cyclin B/Cdk1, cyclin A/Cdk2 and cyclin E/Cdk2, the Cdk inhibitors precipitately induce a dramatic nuclear accumulation of wt p53 and a delocalization of nucleolin from the nucleolus in all interphase cells, whatever their cell cycle status, acting in this way like the DNA-damaging drug, mitomycin C (7 microg/ml). These early events are soon followed by a nucleolar fragmentation in both normal and tumor cells in the presence of the Cdk inhibitors but not in the presence of the DNA-damaging drug. Yet, treatment with either type of compounds eventually triggers rapidly the death of the tumor cells and, much more slowly, that of the normal cells. The Cdk inhibitors, however, stimulate cell death from any stage of the cell cycle, whereas the DNA-damaging drug kills more efficaciously S phase cells. These observations provide a hint that the Cdk2 kinase might be involved in controlling the nuclear levels of the tumor suppressor wt p53 protein and in maintaining the nucleolar integrity and function, linking in this way the cell division cycle machinery to survival functions and overall cell metabolism via the control of nucleocytoplasmic transport and of ribosome production.
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PMID:Potent inhibitors of cyclin-dependent kinase 2 induce nuclear accumulation of wild-type p53 and nucleolar fragmentation in human untransformed and tumor-derived cells. 1060

The CSF-1 receptor (CSF-1R) is expressed in >50% of human breast cancers. To investigate the consequence of CSF-1R expression, hormone-dependent human breast cancer cell lines, MCF-7 and T-47D, were transfected with CSF-1R. Unexpectedly, CSF-1 substantially inhibited estradiol (E2) and insulin-dependent proliferation of MCF-7 transfectants (MCF-7fms) and prevented cyclin E/cdk2 and cyclin A/cdk2 activation, consistent with a G1 arrest. In contrast, CSF-1 increased DNA synthesis in T-47D transfectants (T-47Dfms) alone and with E2 or insulin. In response to CSF-1, there was a marked and sustained upregulation of the cyclin-dependent kinase inhibitor, p21Waf1/Cip1, in MCF-7fms but not T-47Dfms. CSF-1 also markedly upregulated cyclin D1 in MCF-7fms. The coordinate increase in cyclin D1 and p21 had the effect of decreasing the specific but not absolute activity of cyclin D1/cdk4. p53 was not involved since CSF-1 induction of p21 was unaffected by dominant-negative p53 expression. ERK activation by CSF-1 was robust and sustained in MCF-7fms and to a much lesser extent in T-47Dfms. Using pharmacological and transient transfection approaches, we showed that ERK activation was necessary and sufficient for p21 induction in MCF-7fms. Moreover, activated MEK inhibited E2-stimulated cdk2 activity. Our findings indicate that the consequence of CSF-1R-mediated signals in human breast cancer cells is dependent on the genetic background of the particular tumor.
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PMID:CSF-1 activates MAPK-dependent and p53-independent pathways to induce growth arrest of hormone-dependent human breast cancer cells. 1060 7

Human Rec2/Rad51L1 is a member of the Rad51 family of proteins. Although recombinase activity, typical of this family, could not be established, its overexpression in mammalian cells has been shown to cause a delay in G1. Moreover, since hsRec2/Rad51L1 has been found to be induced by both ionizing and UV irradiation, it is likely that hsRec2/Rad51L1 is elevated following any DNA damage and causes a G1 delay to allow time for DNA repair to occur. Limited homology with catalytic domains X and XI of protein kinase A suggested that kemptide, an artificial substrate containing one phosphorylatable residue, a serine, might serve as a substrate for hsRec2/Rad51L1. Here, we report that hsRec2/Rad51L1 can phosphorylate kemptide, as well as myelin basic protein, p53, cyclin E, and cdk2, but not a peptide substrate containing tyrosine only. The finding that hsRec2/Rad51L1 exhibits protein kinase activity is a first step toward identifying a mechanism whereby this protein affects the cell cycle.
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PMID:HsRec2/Rad51L1, a protein influencing cell cycle progression, has protein kinase activity. 1062 63

In search for angiogenesis inhibitors, we tested protease and proteasome inhibitors for the induction of G1 arrest and selective inhibition of growth of human umbilical vein endothelial cells (HUVECs). Serine protease-, cysteine protease-, aspartate protease-, and aminopeptidase-inhibitors did not inhibit bFGF/FBS-induced S-phase induction in HUVECs, but a proteasome inhibitor, lactacystin did inhibit it reversibly. Lactacystin increased the cellular level of p53 and cdk2-associated p21WAF1/CIP1 leading to cdk2 inactivation. In addition to the angiogenesis inhibitor TNP-470, lactacystin also inhibited the growth of HUVECs selectively at about a 20 times lower concentration than that of other human cell lines, including normal fibroblasts and carcinoma cells. Lactacystin induced p53-dependent p21WAF1/CIP1 expression at lower concentrations in HUVECs than in other cells. These cellular effects were also observed with a tripeptide-type proteasome inhibitor, N-Ac-Leu-Leu-norleucinal.
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PMID:Induction of G1 arrest and selective growth inhibition by lactacystin in human umbilical vein endothelial cells. 1062 38

Staurosporine has been reported to cause arrest of cells in G1 phase at low concentration and in G2 phase at high concentration. This raises the question of why the effects of staurosporine on the cell cycle depend on the applied concentration. In order to verify these multiple functions of staurosporine in Meth-A cells, we used cyclin E as a landmark of G1/S transition, cyclin B as a landmark of G2/M transition and MPM2 as a hallmark of M phase. We found that staurosporine arrested cells in G1 phase at a low concentration (20 nM) and in G2/M phase at a high concentration (200 nM). However, 200 nM staurosporine increased the expression of cyclin B and cdc2 proteins, suggesting that the cells progressed through the G2/M transition, and increased the expression of MPM2 protein, indicating that the cells entered M phase. Moreover, 200 nM staurosporine increased the expression of p53 and p21 proteins and inhibited the expression of cyclin E and cdk2 proteins, suggesting that the cells were arrested in the G1 phase of the next cycle. Morphological observation showed similar results as well. These data suggest that the G2/M accumulation induced by 200 nM staurosporine does not reflect G2 arrest, but rather results from M phase arrest, followed by progression from M phase to the G1 phase of the next cycle without cytokinesis, and finally arrest of the cells in G1 phase.
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PMID:Both low and high concentrations of staurosporine induce G1 arrest through down-regulation of cyclin E and cdk2 expression. 1069 60

Elevation of the cyclin-dependent kinase (cdk) inhibitor, p27(kip1) is necessary for Interleukin (IL)-4-mediated growth arrest of human low grade astrocytoma (RTLGA) cells and occurs at 24 h of treatment. Pathways involved in IL4 alteration of p27(kip1) are unknown, however. Here we investigated whether other cdk inhibitors contributed to the actions of IL-4 on RTLGA cells. By 12 h of IL-4 treatment, both cdk4 and cdk2 kinase activities against the retinoblastoma protein (pRb) were reduced and nuclear entry of pRb was prohibited. Twelve-hour cdk complexes contained elevated p21(waf1/cip1) but not p27(kip1), p15(ink4B) or p16(ink4A). IL-4 increased p21(waf1/cip1) but not p27(kip1) mRNA levels, and stimulated luciferase activity of a p21(waf1/cip1) promoter-luciferase reporter. In p53-mutant WITG3 cells, IL-4 did not alter p21(waf1/cip1) mRNA and promoter-luciferase activity or p27(kipl) protein, suggesting a need for functional p53. STAT6 phosphorylation by IL-4, however, occurred in both p53-mutant WITG3 and p53-functional RTLGA cells. Pre-treatment of RTLGA with anti-sense but not missense p21(waf1/cip1) oligonucleotide prior to IL-4: (a) restored cdk activities; (b) reduced cdk4-associated p21(waf1/cip1) levels; (c) prevented p27(kipl) elevation; and (d) reversed growth arrest. These results are the first to suggest that p21(waf1/cip1) is essential for IL-4-mediated elevation of p27(kip) and growth arrest of astrocytoma cells.
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PMID:Anti-sense oligonucleotide of p21(waf1/cip1) prevents interleukin 4-mediated elevation of p27(kip1) in low grade astrocytoma cells. 1069 11

Previous studies have shown that TGFbeta1 expression is upregulated in mouse keratinocytes infected with a v-rasHa retrovirus, although the functional significance of this has not been clear. Here we show that v-rasHa retrovirus transduced primary mouse keratinocytes undergo hyperproliferation followed by a TGFbeta1 dependent G1 growth arrest and senescence. The growth arrest is accompanied by a 15-fold increase in total TGFbeta1 secreted and a fourfold increase in secreted active TGFbeta1. When cultured in the presence of a neutralizing antibody to TGFbeta1, the senescence response is suppressed. Levels of the TGFbeta1 target p15ink4b increase during senescence as does association of this kinase inhibitor with cyclinD/cdk4 complexes. However, p16ink4a, p53 and p19ARF expression also increase during senescence. Genetic analysis shows that TGFbeta1 null and dominant negative TbetaBRII expressing v-rasHa keratinocytes resist the G1 growth arrest and do not senescence. This resistance is associated with low expression of p15ink4b and p16ink4a, constitutive Rb phosphorylation and high levels of cdk4 and cdk2 kinase activity. In contrast, inactivation of TGFbetabeta1 secretion or response does not block the induction of p53 and p19ARF, but the level of p21waf1, a p53 target gene, is reduced in cyclin D/cdk4 and cyclin E/cdk2 complexes. Thus, although multiple senescence pathways are activated in response to a ras oncogene, inactivation of TGFbeta1 secretion or response is sufficient to block the senescence program. Since v-rasHa transduced TGFbeta1-/- keratinocytes form squamous cell carcinomas following skin grafting, these results suggest that in mouse keratinocytes, defects in TGFbeta1 signaling accelerate malignant progression by overcoming oncogene induced replicative senescence.
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PMID:Defects in TGF-beta signaling overcome senescence of mouse keratinocytes expressing v-Ha-ras. 1076 27

Human papillomavirus (HPV) survives by reactivating DNA replication in post-mitotic cells. In the present study, we describe a mouse model of HPV-dependent disease. In these mice, DNA synthesis is activated in suprabasal keratinocytes, leading to acanthosis, parakeratosis and enhanced desquamation. The full-length E6/E7 transcript and two alternately spliced products are produced and in most lines the predominant product is E6*. In the present study, we examine the effects of E6/E7 on cell cycle regulatory protein expression. E6/E7 expression in mouse epidermis is correlated with increased levels of the p53, p21, p27, cdk2, cdk4, cdk6, cyclin D1 and cyclin E regulatory proteins. Hyperproliferation is also observed in the buccal mucosa and the tongue epithelia of E6/E7 mice, and p53 levels are markedly increased in these epithelia. These results suggest that the major changes in cell cycle regulatory protein expression are in response to the presence of E7 and that E6 has a lesser impact.
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PMID:Suprabasal expression of the human papillomavirus type 16 oncoproteins in mouse epidermis alters expression of cell cycle regulatory proteins. 1078 29

Productive high-titer infection by human immunodeficiency virus type 1 (HIV-1) requires the activation of target cells. Infection of quiescent peripheral CD4 lymphocytes by HIV-1 results in incomplete, labile reverse transcripts and lack of viral progeny formation. An interplay between Tat and p53 has previously been reported, where Tat inhibited the transcription of the p53 gene, which may aid in the development of AIDS-related malignancies, and p53 expression inhibited HIV-1 long terminal repeat transcription. Here, by using a well-defined and -characterized stress signal, gamma irradiation, we find that upon gamma irradiation, HIV-1-infected cells lose their G(1)/S checkpoints, enter the S phase inappropriately, and eventually apoptose. The loss of the G(1)/S checkpoint is associated with a loss of p21/Waf1 protein and increased activity of a major G(1)/S kinase, namely, cyclin E/cdk2. The p21/Waf1 protein, a known cyclin-dependent kinase inhibitor, interacts with the cdk2/cyclin E complex and inhibits progression of cells into S phase. We find that loss of the G(1)/S checkpoint in HIV-1-infected cells may in part be due to Tat's ability to bind p53 (a known activator of the p21/Waf1 promoter) and sequester its transactivation activity, as seen in both in vivo and in vitro transcription assays. The loss of p21/Waf1 in HIV-1-infected cells was specific to p21/Waf1 and did not occur with other KIP family members, such as p27 (KIP1) and p57 (KIP2). Finally, the advantage of a loss of the G(1)/S checkpoint for HIV-1 per se may be that it pushes the host cell into the S phase, which may then allow subsequent virus-associated processes, such as RNA splicing, transport, translation, and packaging of virion-specific genes, to occur.
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PMID:Loss of G(1)/S checkpoint in human immunodeficiency virus type 1-infected cells is associated with a lack of cyclin-dependent kinase inhibitor p21/Waf1. 1079 78

The mechanism of growth inhibition and triggering of cell death by the antibiotic brefeldin A (BFA) was investigated in human prostatic cancer DU-145 cells. After cells were cultured with various concentrations of BFA, cell number and viability were determined at specified times. Compared with untreated cells, a drastic growth reduction (>80%) with approximately 50% cell death was observed in the cells cultured with BFA (30 ng/mL) for 72 h. Cell-cycle analysis using flow cytometry revealed that such growth inhibition was associated with approximately 85% reduction in the S-phase population, indicating the inhibition of the G(1)-S phase progression. Western blots further showed that cell-cycle-dependent kinases (cdk2 and cdk4), cyclin D(1), and p53 were all downregulated, whereas WAF1 (p21) was upregulated with BFA treatment. Possible induction of apoptosis by BFA was also assessed by TUNEL assay and by DNA analysis using agarose gel electrophoresis. The TUNEL assay demonstrated the positive staining of BFA-treated cells, and gel electrophoresis confirmed nucleosomal DNA ladder formation. Thus, these results suggest that growth inhibition of DU-145 cells by BFA is attributable mainly to a G1 cell-cycle arrest through the modulation of specific cell-cycle regulators. The accompanying cell death may follow a p53-independent apoptotic pathway.
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PMID:Mechanism of Brefeldin A-Induced Growth Inhibition and Cell Death in Human Prostatic Carcinoma Cells. 1085 Dec 91


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