Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Huanglian is an herb that is widely used in China for the treatment of gastroenteritis. We elected to determine whether huanglian could inhibit tumor cell growth by modulating molecular events directly associated with the cell cycle. Huanglian inhibited tumor growth and colony formation of gastric, colon, and breast cancer cell lines in a time- and dose-dependent manner. Cell growth was completely inhibited after 3 days of continuous drug exposure to 10 microg/ml of herb. This degree of growth inhibition was significantly greater than that observed with berberine, the major constituent of the herb. The inhibition of cell growth by huanglian was associated with up to 8-fold suppression of cyclin B1 protein. This resulted in complete inhibition of cdc2 kinase activity and accumulation of cells in G(2). The mRNA expression of cyclin B1 was not changed after huanglian treatment. There was no change in the protein expression of cyclins A or E. Therefore, the effect of huanglian on inhibiting tumor growth seems to be mediated by the selective suppression of cyclin B1, which results in the inhibition of cdc2 kinase activity. Inhibition of cyclin dependent kinase (cdk) activity is emerging as an attractive target for cancer chemotherapy. Huanglian represents a class of agents that can inhibit tumor cell growth by directly suppressing the expression of a cyclin subunit that is critical for cell cycle progression. These results indicate that traditional Chinese herbs may represent a new source of agents designed for selective inhibition of cyclin dependent kinases in cancer therapy.
Mol Pharmacol 2000 Dec
PMID:Huanglian, A chinese herbal extract, inhibits cell growth by suppressing the expression of cyclin B1 and inhibiting CDC2 kinase activity in human cancer cells. 1109 65

Morphological and biochemical changes indicative of cytoplasmic maturation in relation to nuclear maturation progression and early embryo developmental potential was studied. Fluorescently labeled microfilaments and cortical granules were visualized by using laser scanning confocal microscopy. The mitogen-activated protein (MAP) kinase phosphorylation and cyclin B1 levels were revealed by Western blot. With the maturation of oocytes, cortical granules and microfilaments were localized at the cell cortex. A cortical granule-free domain (CGFD) and an actin-thickening area were observed over both the MII spindle of a mature oocyte and chromosomes of a nocodazole-treated oocyte, suggesting that chromosomes, but not the spindle, determined the localization of CGFD and actin-thickening area. In oocytes that are incompetent to resume meiosis, as indicated by the failure of germinal vesicle breakdown (GVBD), peripheral localization of cortical granules and microfilaments, phosphorylation of MAP kinase and synthesis of cyclin B1 did not occur after 44 hr in vitro. These cytoplasmic changes were also blocked when GVBD of meiotically competent oocytes was inhibited by cycloheximide. Culture of oocytes in a chemically defined medium showed that biological factors such as gonadotropins, cumulus cells and follicle size affected both nuclear and cytoplasmic maturation as well as embryo developmental potential. Absence of gonadotropins or removal of cumulus cells alone did not significantly influence GVBD or cyclin B1 levels, but decreased the final maturation and developmental ability of oocytes. A combination of gonadotropin absence and cumulus removal decreased GVBD, MAP kinase phosphorylation and embryo development. A high proportion of oocytes derived from small follicles were able to resume meiosis, synthesize cyclin B(1), phosphorylate MAP kinase and translocate CGs, but their maturation and embryo developmental ability were limited. Removal of cumulus cells from small follicle-derived oocytes severely affected their ability to undergo cytoplasmic and nuclear maturation.
Mol Reprod Dev 2001 Jun
PMID:Cytoplasmic changes in relation to nuclear maturation and early embryo developmental potential of porcine oocytes: effects of gonadotropins, cumulus cells, follicular size, and protein synthesis inhibition. 1138 54

Cyclin B, the regulatory subunit of maturation-promoting factor (MPF), comprises several subtypes that are presumed to confer different functions on MPF although no direct evidence has been provided to date. To clarify the difference in the roles of cyclins B1 and B2, we used frog (Rana japonica) oocytes in which MPF is formed only after progesterone stimulation because it is possible to produce oocytes containing either cyclin B1-MPF or cyclin B2-MPF by antisense RNA-mediated translational inhibition of each mRNA. Using this advantage, we investigated the functions of cyclins B1 and B2 and obtained the following results: (a) oocytes synthesizing cyclin B2-MPF underwent meiosis I and II with formation of a bipolar spindle at each metaphase; (b) oocytes synthesizing cyclin B1-MPF formed a monopolar spindle at metaphase I and extruded an abnormal polar body; and (c) both oocytes underwent germinal vesicle breakdown (GVBD) and chromosome condensation. Immunocytochemical observations also revealed continuous localization of cyclin B2 on the spindle during meiosis. These results provide evidence of the requirement of cyclin B2, but not cyclin B1, for organizing the bipolar spindle, though either cyclin B1 or B2 is redundant for inducing GVBD and chromosome condensation.
Mol Reprod Dev 2001 Jun
PMID:Requirement of cyclin B2, but not cyclin B1, for bipolar spindle formation in frog (Rana japonica) oocytes. 1138 55

Detailed investigations have addressed the infection pathway of recombinant adenovirus (Ad) gene transfer vectors, but little attention has been paid to the influence of cell physiology on the outcome of Ad infection. Based on observations that Ad infection of clonal cell populations show cell-to-cell variability in the extent of capsid binding, we hypothesized that the cell cycle may influence the outcome of Ad infection. To address this hypothesis, we evaluated Ad association with cells in both unsynchronized and pharmacologically synchronized cell populations. In unsynchronized cell populations, elevated Ad association with cells correlated with expression of cyclin B1, a marker of entry into the M phase of mitosis. The same analysis conducted on cell populations that were synchronized at M phase (using paclitaxel or nocodazole) or at S phase (using aphidicolin) confirmed that M phase cells bound three- to sixfold more capsid compared with unsynchronized cells, which are primarily in the G(1) and G(2) phases. The elevated association of vectors with cells translated into 2.5- to 4-fold greater transgene expression 24 hours after infection. Assessment of cell surface expression of Ad receptors demonstrated that both the high-affinity coxsackie-adenovirus receptor for Ad fiber protein and the low-affinity alpha(v) integrin receptor for Ad penton base protein showed increased cell surface expression at M phase (1.5-fold and 2- to 3-fold increases, respectively). These data demonstrate that Ad infection of a homogenous population of cells can vary depending on the cell cycle stage, with enhanced Ad binding and expression correlating with the enhanced expression of Ad receptors during M phase. These observations have relevance to understanding the mechanisms of gene transfer by Ad vectors and should help in the design of in vivo gene transfer strategies.
Mol Ther 2001 Jul
PMID:Variation in adenovirus receptor expression and adenovirus vector-mediated transgene expression at defined stages of the cell cycle. 1147 1

In mitosis, the anaphase-promoting complex (APC) regulates the onset of sister-chromatid separation and exit from mitosis by mediating the ubiquitination and degradation of the securin protein and mitotic cyclins. With the use of a baculoviral expression system, we have reconstituted the ubiquitin ligase activity of human APC. In combination with Ubc4 or UbcH10, a heterodimeric complex of APC2 and APC11 is sufficient to catalyze the ubiquitination of human securin and cyclin B1. However, the minimal APC2/11 ubiquitin ligase module does not possess substrate specificity, because it also ubiquitinates the destruction box deletion mutants of securin and cyclin B1. Both APC11 and UbcH10 bind to the C-terminal cullin homology domain of APC2, whereas Ubc4 interacts with APC11 directly. Zn(2+)-binding and mutagenesis experiments indicate that APC11 binds Zn(2+) at a 1:3 M ratio. Unlike the two Zn(2+) ions of the canonical RING-finger motif, the third Zn(2+) ion of APC11 is not essential for its ligase activity. Surprisingly, with Ubc4 as the E2 enzyme, Zn(2+) ions alone are sufficient to catalyze the ubiquitination of cyclin B1. Therefore, the Zn(2+) ions of the RING finger family of ubiquitin ligases may be directly involved in catalysis.
Mol Biol Cell 2001 Dec
PMID:APC2 Cullin protein and APC11 RING protein comprise the minimal ubiquitin ligase module of the anaphase-promoting complex. 1173 84

Apigenin, a nonmutagenic flavonoid, has been shown to inhibit ultraviolet light-induced skin tumorigenesis when topically applied to mouse skin. Our previous studies have shown that apigenin treatment of cultured mouse keratinocytes induces G(2)/M arrest accompanied by an increase in p53 protein stability and expression of p21(waf1). In this study, we determined whether the G(2)/M arrest induced by apigenin was dependent upon the presence of the cyclin dependent kinase inhibitor p21(waf1). We exposed WWT.8 (p21(waf1) wild-type) and WKO.16 (p21(waf1) null) mouse keratinocytes to various doses of apigenin for 24 h and observed G(2)/M arrest in both cell lines, thereby establishing that the apigenin-induced G(2)/M arrest was p21(waf1) independent. A 4-h treatment with apigenin induced increases in p53 protein level by sixfold and tenfold in the WWT.8 p21(waf1) wild-type cells and WKO.16 p21(waf1) null cells, respectively. After 24 h in WWT.8 cells, p21(waf1) protein also was induced in a dose-dependent manner, but it was not expressed in WKO.16 keratinocytes. We then measured the effect of apigenin treatment on the mammalian homologue of the yeast cdc2 gene (p34(cdc2)) cyclin-dependent kinase and cyclin B1 (cycB1), because these proteins complex to regulate G(2)/M progression. Apigenin treatment decreased the protein level of p34(cdc2), and p34(cdc2) kinase activity was inhibited in both p21(waf1)(+/+) and p21(waf1)(-/-) cell lines by approximately 40%. The inhibition of p34(cdc2) kinase activity by apigenin treatment correlated with increasing levels of p34(cdc2) phosphorylation at Tyr15, a site in the p34(cdc2) kinase that undergoes inhibitory phosphorylation by Wee1 kinase. Apigenin treatment also had no effect on the protein level or activity of the competing phosphatase, cdc25c, which dephosphorylates p34(cdc2) kinase at Tyr15. Apigenin had little effect on the accumulation of cycB1 protein. These results supported the conclusion that G(2)/M arrest induced by apigenin was accompanied by inhibition of the p34(cdc2) cyclin-dependent kinase protein level and activity in a p21(waf1)-independent manner.
Mol Carcinog 2002 Jan
PMID:A p21(waf1)-independent pathway for inhibitory phosphorylation of cyclin-dependent kinase p34(cdc2) and concomitant G(2)/M arrest by the chemopreventive flavonoid apigenin. 1180 56

1. The ubiquitin-proteasome pathway is involved in a variety of cellular functions in mammalian cells. The role of proteasome, however, in the course of cell differentiation is not well characterized. We hypothesized that proteasome activity might be essential during neuronal cell differentiation. 2. To investigate the role of proteasome during neuronal differentiation, we made use of a murine neuroblastoma cell line (NBP2) that terminally differentiates into mature neurons upon elevation of the intracellular level of adenosine 3',5'-cyclic monophosphate (cAMP). To monitor proteasome activity in NBP2 cells, we integrated an expression cassette for a short-lived green fluorescent protein (d2EGFP) into these cells, which were designated as NBP2-PN25. When NBP2-PN25 cells were treated with a proteasome inhibitor, lactacystin or MG132, a dose-dependent increase in the constitutive levels of d2EGFP expression was detected. 3. We also found that proteasome inhibition by lactacystin during the cAMP-induced differentiation of NBP2-PN25 cells triggered cell death. Both lactacystin and cAMP induction reduced the expression of mRNA for the differentiation-associated genes, such as N-myc and cyclin B1. While cAMP-inducing agents decreased the level of N-myc and cyclin B1 proteins, lactacystin increased the level of these proteins. 4. Our data suggest that a reduced level of N-myc and cyclin B1 proteins is critical to commence differentiation, and this can be blocked by a proteasome inhibitor, leading to cell death. Concomitant induction of differentiation and proteasome inhibition, may, therefore, be potentially useful for the treatment of human neuroblastomas.
Cell Mol Neurobiol 2001 Oct
PMID:Proteasome activity is critical for the cAMP-induced differentiation of neuroblastoma cells. 1186 Jan 88

While transport of RNA-binding protein HuR from nucleus to cytoplasm is emerging as a key regulatory step for HuR function, the mechanisms underlying this process remain poorly understood. Here, we report that the AMP-activated kinase (AMPK), an enzyme involved in responding to metabolic stresses, potently regulates the levels of cytoplasmic HuR. Inhibition of AMPK, accomplished either through cell treatment or by adenovirus infection to express dominant-negative AMPK, was found to increase the level of HuR in the cytoplasm and to enhance the binding of HuR to p21, cyclin B1, and cyclin A mRNA transcripts and elevate their expression and half-lives. Conversely, AMPK activation, achieved by means including infection to express constitutively active AMPK, resulted in reduced cytoplasmic HuR; decreased levels and half-lives of mRNAs encoding p21, cyclin A, and cyclin B1; and diminished HuR association with the corresponding transcripts. We therefore propose a novel function for AMPK as a regulator of cytoplasmic HuR levels, which in turn influences the mRNA-stabilizing function of HuR and the expression of HuR target transcripts.
Mol Cell Biol 2002 May
PMID:AMP-activated kinase regulates cytoplasmic HuR. 1197 74

Cyclin B1, which plays a key role in the control of cell cycle progression from G(2) through M phase, was recently identified by us as a tumor antigen recognized by human T-cells. To understand what makes this normal molecule antigenic, we compared its expression in malignant versus normal cells. Immunohistology showed overexpression of cyclin B1 protein in tumors compared to surrounding normal tissue and localization in the cytoplasm rather than the nucleus. Cyclin B1 is overexpressed at protein and mRNA level in many tumor cell lines including breast, lung, colorectal carcinoma, lymphoma and leukemia. While overexpressed in tumor cells at all stages of the cell cycle, its expression still peaks at G(2)/M phase, as it does in normal cells. We compared cyclin B1 expression in two cell clones derived from the same colorectal tumor cell line, one wild type for p53 (HCT116p53(+/+)) and one with deleted p53 (HCT116p53(-/-)). HCT116p53(+/+) cells had undetectable (normal) level of cyclin B1 protein, while HCT116p53(-/-) cells showed overexpression. When reconstituted with p53, HCT116p53(-/-) cells reverted to normal cyclin B1 expression. We conclude that p53 plays an important role in cyclin B1 regulation and that tumors with mutated p53 will be good candidates for cyclin B1 based immunotherapy.
Mol Immunol 2002 May
PMID:Immune recognition of cyclin B1 as a tumor antigen is a result of its overexpression in human tumors that is caused by non-functional p53. 1200 77

Arsenic trioxide (As(2)O(3)) has been found to induce apoptosis in leukemia cell lines and clinical remissions in patients with acute promyelocytic leukemia. In this study, we investigated the cytotoxic effect and mechanisms of action of As(2)O(3) in human tumor cell lines. As(2)O(3) caused inhibition of cell growth (IC(50) range, 3-14 microM) in a variety of human solid tumor cell lines, including four human non-small-cell lung cancer cell lines (H460, H322, H520, H661), two ovarian cancer cell lines (SK-OV-03, A2780), cervical cancer HeLa, and breast carcinoma MCF-7, as assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Flow cytometry analysis showed that As(2)O(3) treatment resulted in a time-dependent accumulation of cells in the G(2)/M phase. We observed, using Wright-Giemsa and 4',6-diamidine-2-phenylindole-dihydrochloride staining, that As(2)O(3) blocked the cell cycle in mitosis. In vitro examination revealed that As(2)O(3) markedly promoted tubulin polymerization without affecting GTP binding to beta-tubulin. Immunocytochemical and EM studies of treated MCF-7 cells showed that As(2)O(3) treatment caused changes in the cellular microtubule network and formation of polymerized microtubules. Similar to most anti-tubulin agents, As(2)O(3) treatment induced up-regulation of the cyclin B1 levels and activation of p34(cdc2)/cyclinB1 kinase, as well as Bcl-2 phosphorylation. Furthermore, activation of caspase-3 and -7 and cleavage of poly(ADP-ribose) polymerase and beta-catenin occurred only in As(2)O(3)-induced mitotic cells, not in interphase cells, suggesting that As(2)O(3)-induced mitotic arrest may be a requirement for the activation of apoptotic pathways. In addition, As(2)O(3) exhibited similar inhibitory effects against parental MCF-7, P-glycoprotein-overexpressing MCF-7/doxorubicin cells, and multidrug resistance protein (MRP)-expressing MCF-7/etoposide cells (resistance indices, 2.3 and 1.9, respectively). Similarly, As(2)O(3) had similar inhibitory effect against parental ovarian carcinoma A2780 cells and tubulin mutation paclitaxel-resistant cell lines PTx10 and PTx22 (resistance indices, 0.86 and 0.93, respectively), suggesting that its effect on tubulin polymerization and G(2)/M phase arrest is distinct from that of paclitaxel. Taken together, our data demonstrate that As(2)O(3) has a paclitaxel-like effect, markedly promotes tubulin polymerization, arrests cell cycle at mitosis, and induces apoptosis. In addition, As(2)O(3) is a poor substrate for transport by P-glycoprotein and MRP, and non-cross-resistant with paclitaxel resistant cell lines due to tubulin mutation, suggesting that As(2)O(3) may be useful for treatment of human solid tumors, particularly in patients with paclitaxel resistance.
Mol Pharmacol 2002 Sep
PMID:Arsenic trioxide produces polymerization of microtubules and mitotic arrest before apoptosis in human tumor cell lines. 1218 29


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