共查询到20条相似文献,搜索用时 31 毫秒
1.
Anna Lena Illert Michael Zech Cathrin Moll Corinna Albers Stefanie Kreutmair Christian Peschel Florian Bassermann Justus Duyster 《The Journal of biological chemistry》2012,287(45):37997-38005
NIPA is an F-box-like protein that contributes to the timing of mitotic entry. It targets nuclear cyclin B1 for ubiquitination in interphase, whereas in G2/M phase, NIPA is inactivated by phosphorylation to allow for cyclin B1 accumulation, a critical event for proper G2/M transition. We recently specified three serine residues of NIPA and demonstrated a sequential phosphorylation at G2/M, where initial Ser-354 and Ser-359 phosphorylation is most crucial for SCFNIPA inactivation. In this study, we identified ERK2 as the kinase responsible for this critical initial phosphorylation step. Using in vitro kinase assays, we found that both ERK1 and ERK2 phosphorylated NIPA with high efficiency. Mutation of either Ser-354 or Ser-359 abolished ERK-dependent NIPA phosphorylation. Pharmacologic inhibition of ERK1/2 in cell lines resulted in decreased NIPA phosphorylation at G2/M. By combining cell cycle synchronization with stable expression of shRNA targeting either ERK1 or ERK2, we showed that ERK2 but not ERK1 mediated NIPA inactivation at G2/M. ERK2 knockdown led to a delay at the G2/M transition, a phenotype also observed in cells expressing a phospho-deficient mutant of NIPA. Thus, our data add to the recently described divergent functions of ERK1 and ERK2 in cell cycle regulation, which may be due in part to the differential ability of these kinases to phosphorylate and inactivate NIPA at G2/M. 相似文献
2.
Objectives: Tumour cells respond to ionizing radiation by cycle arrest, cell death or repair and possible regrowth. We have developed a dynamic mathematical model of the cell cycle to incorporate transition probabilities for entry into DNA replication and mitosis. In this study, we used the model to analyse effects of radiation on cultures of five human melanoma cell lines. Materials and methods: Cell lines were irradiated (9 Gy) prior to further culture and harvesting at multiple points up to 96 h later. Cells were fixed, stained with propidium iodide and analysed for G1‐, S‐ and G2/M‐phase cells by flow cytometry. Data for all time points were fitted to a mathematical model. To provide unique solutions, cultures were grown in the presence and absence of the mitotic poison paclitaxel, added to prevent cell division. Results: The model demonstrated that irradiation at 9 Gy induced G2‐phase arrest in all lines for at least 96 h. Two cell lines with wild‐type p53 status additionally exhibited G1‐phase arrest with recovery over 15 h, as well as evidence of cell loss. Resumption of cycling of surviving cells, as indicated by increases in G1/S and G2/M‐phase transitions, was broadly comparable with results of clonogenic assays. Conclusions: The results, combined with existing data from clonogenic survival assays, support the hypothesis that a dominant effect of radiation in these melanoma lines is the induction of long‐term cell cycle arrest. 相似文献
3.
Lee YS Choi KM Choi MH Ji SY Lee S Sin DM Oh KW Lee YM Hong JT Yun YP Yoo HS 《Cell proliferation》2011,44(4):320-329
Objectives: Melanoma is the most aggressive form of skin cancer, and it resists chemotherapy. Candidate drugs for effective anti‐cancer treatment have been sought from natural resources. Here, we have investigated anti‐proliferative activity of myriocin, serine palmitoyltransferase inhibitor, in the de novo sphingolipid pathway, and its mechanism in B16F10 melanoma cells. Material and methods: We assessed cell population growth by measuring cell numbers, DNA synthesis, cell cycle progression, and expression of cell cycle regulatory proteins. Ceramide, sphingomyelin, sphingosine and sphingosine‐1‐phosphate levels were analysed by HPLC. Results: Myriocin inhibited proliferation of melanoma cells and induced cell cycle arrest in the G2/M phase. Expressions of cdc25C, cyclin B1 and cdc2 were decreased in the cells after exposure to myriocin, while expression of p53 and p21waf1/cip1 was increased. Levels of ceramide, sphingomyelin, sphingosine and sphingosine‐1‐phosphate in myriocin‐treated cells after 24 h were reduced by approximately 86%, 57%, 75% and 38%, respectively, compared to levels in control cells. Conclusions: Our results suggest that inhibition of sphingolipid synthesis by myriocin in melanoma cells may inhibit expression of cdc25C or activate expression of p53 and p21waf1/cip1, followed by inhibition of cyclin B1 and cdc2, resulting in G2/M arrest of the cell cycle and cell population growth inhibition. Thus, modulation of sphingolipid metabolism by myriocin may be a potential target of mechanism‐based therapy for this type of skin cancer. 相似文献
4.
The effect of sodium butyrate on cell proliferation was studied in eight human urothelial cell lines differing in transformation grade (TGr): Hu 1752 (mortal, TGr I); HCV29 (immortal and tumorigenic, TGr II); HCV29T, T24, T24A, T24B, Hu 961A and Hu 1703He (tumorigenic, TGr III). In all cell lines, except Hu 1752, addition of 4 mm sodium butyrate at 18 h after replating resulted in a significantly decreased population of adherent cells after a further 24–48 h. This might partially be explained by detachment of cells, probably mainly S phase cells, from the substrate in the lines HCV 29, HCV29T, Hu 961A and Hu 1703He. Flow cytometric DNA analysis of the adherent cell population showed that all TGr II and III urothelial cell lines were DNA aneuploid, and that butyrate perturbed the cell cycle distribution in these cell lines, mainly by a decrease of the S phase fraction. Flow cytometric bromodeoxyuridine (BrdUrd)/DNA analysis of continuously BrdUrd labelled cultures, using a ‘washless’ BrdUrd/DNA staining technique, showed that butyrate inhibited the G0/1-S phase transition, indicated by a delayed depletion of BrdUrd negative G0/1 cells in the cell lines HCV29, HCV29T, T24B, Hu 961A and Hu 1703He. BrdUrd/DNA analysis further showed that butyrate inhibited the G2M-G0/1 phase transition, indicated by a pronounced accumulation of BrdUrd positive G2M cells in the cell lines HCV29T, T24B, Hu 961A and Hu 1703He. Microscopy of HCV29T and Hu 961A cells indicated that this block did not occur in mitosis. The parental cell line T 24 and the cell line T 24 A did not show an accumulation of BrdUrd negative G0/1 cells or BrdUrd positive G2M cells like that occurring in the derived cell line T 24B. 相似文献
5.
Skp2 regulates G2/M progression in a p53-dependent manner 总被引:1,自引:0,他引:1
Targeted proteasomal degradation mediated by E3 ubiquitin ligases controls cell cycle progression, and alterations in their activities likely contribute to malignant cell proliferation. S phase kinase-associated protein 2 (Skp2) is the F-box component of an E3 ubiquitin ligase complex that targets p27Kip1 and cyclin E1 to the proteasome. In human melanoma, Skp2 is highly expressed, regulated by mutant B-RAF, and required for cell growth. We show that Skp2 depletion in melanoma cells resulted in a tetraploid cell cycle arrest. Surprisingly, co-knockdown of p27Kip1 or cyclin E1 failed to prevent the tetraploid arrest induced by Skp2 knockdown. Enhanced Aurora A phosphorylation and repression of G2/M regulators cyclin B1, cyclin-dependent kinase 1, and cyclin A indicated a G2/early M phase arrest in Skp2-depleted cells. Furthermore, expression of nuclear localized cyclin B1 prevented tetraploid accumulation after Skp2 knockdown. The p53 status is most frequently wild type in melanoma, and the tetraploid arrest and down-regulation of G2/M regulatory genes were strongly dependent on wild-type p53 expression. In mutant p53 melanoma lines, Skp2 depletion did not induce cell cycle arrest despite up-regulation of p27Kip1. These data indicate that elevated Skp2 expression may overcome p53-dependent cell cycle checkpoints in melanoma cells and highlight Skp2 actions that are independent of p27Kip1 degradation. 相似文献
6.
Xiaohong Cao A. H. Wang R. Z. Jiao C. L. Wang D. Z. Mao L. Yan B. Zeng 《Cell biochemistry and biophysics》2009,55(3):163-171
Surfactin, purified from Bacillus subtilis natto TK-1, inhibited proliferation of human breast cancer MCF-7 cells in a dose- and time-dependent manner, with IC50 at 24, 48, and 72 h of 82.6, 27.3, and 14.8 μM, respectively. Surfactin-induced cell death was considered to be apoptotic
by observing the typical apoptotic morphological change by acridine orange/ethidium bromide staining and Transferase-mediated
dUTP Nick End-labeling assay. [Ca2+]i measurement revealed that surfactin induced a sustained increase in concentration of intracellular [Ca2+]i. Flow cytometric analysis also demonstrated that surfactin caused time-dependent apoptosis of MCF-7 cells through cell
arrest at G2/M phase. Western blot revealed that surfactin induced accumulation of the tumor suppressor p53 and cyclin kinase inhibitor
p21waf1/cip1, and inhibited the activity of the G2-specific kinase, cyclin B1/p34cdc2. Based on our findings, surfactin inhibited proliferation in MCF-7 cells by inducing apoptosis and the elevation of [Ca2+]i may play an important role in the apoptosis. The mechanism which surfactin caused G2/M arrest seems to be through cell cycle factor regulation. 相似文献
7.
Xiaoying Zhang Wei Chen Ruth Guillermo Gudiseva Chandrasekher Radhey S Kaushik Alan Young Hesham Fahmy Chandradhar Dwivedi 《BMC research notes》2010,3(1):220
Background
α-Santalol, an active component of sandalwood oil, has shown chemopreventive effects on skin cancer in different murine models. However, effects of α-santalol on cell cycle have not been studied. Thus, the objective of this study was to investigate effects of α-santalol on cell cycle progression in both p53 mutated human epidermoid carcinoma A431 cells and p53 wild-type human melanoma UACC-62 cells to elucidate the mechanism(s) of action.Methods
MTT assay was used to determine cell viability in A431 cells and UACC-62; fluorescence-activated cell sorting (FACS) analysis of propidium iodide staining was used for determining cell cycle distribution in A431 cells and UACC-62 cells; immunoblotting was used for determining the expression of various proteins and protein complexes involved in the cell cycle progression; siRNA were used to knockdown of p21 or p53 in A431 and UACC-62 cells and immunofluorescence microscopy was used to investigate microtubules in UACC-62 cells.Results
α-Santalol at 50-100 μM decreased cell viability from 24 h treatment and α-santalol at 50 μM-75 μM induced G2/M phase cell cycle arrest from 6 h treatment in both A431 and UACC-62 cells. α-Santalol altered expressions of cell cycle proteins such as cyclin A, cyclin B1, Cdc2, Cdc25c, p-Cdc25c and Cdk2. All of these proteins are critical for G2/M transition. α-Santalol treatment up-regulated the expression of p21 and suppressed expressions of mutated p53 in A431 cells; whereas, α-santalol treatment increased expressions of wild-type p53 in UACC-62 cells. Knockdown of p21 in A431 cells, knockdown of p21 and p53 in UACC-62 cells did not affect cell cycle arrest caused by α-santalol. Furthermore, α-santalol caused depolymerization of microtubules similar to vinblastine in UACC-62 cells.Conclusions
This study for the first time identifies effects of α-santalol in G2/M phase arrest and describes detailed mechanisms of G2/M phase arrest by this agent, which might be contributing to its overall cancer preventive efficacy in various mouse skin cancer models.8.
Mouse hepatitis virus (MHV) replication in actively growing DBT and 17Cl-1 cells resulted in the inhibition of host cellular DNA synthesis and the accumulation of infected cells in the G0/G1 phase of the cell cycle. UV-irradiated MHV failed to inhibit host cellular DNA synthesis. MHV infection in quiescent 17Cl-1 cells that had been synchronized in the G0 phase by serum deprivation prevented infected cells from entering the S phase after serum stimulation. MHV replication inhibited hyperphosphorylation of the retinoblastoma protein (pRb), the event that is necessary for cell cycle progression through late G1 and into the S phase. While the amounts of the cellular cyclin-dependent kinase (Cdk) inhibitors p21Cip1, p27Kip1, and p16INK4a did not change in infected cells, MHV infection in asynchronous cultures induced a clear reduction in the amounts of Cdk4 and G1 cyclins (cyclins D1, D2, D3, and E) in both DBT and 17Cl-1 cells and a reduction in Cdk6 levels in 17Cl-1 cells. Infection also resulted in a decrease in Cdk2 activity in both cell lines. MHV infection in quiescent 17Cl-1 cells prevented normal increases in Cdk4, Cdk6, cyclin D1, and cyclin D3 levels after serum stimulation. The amounts of cyclin D2 and cyclin E were not increased significantly after serum stimulation in mock-infected cells, whereas they were decreased in MHV-infected cells, suggesting the possibility that MHV infection may induce cyclin D2 and cyclin E degradation. Our data suggested that a reduction in the amounts of G1 cyclin-Cdk complexes in MHV-infected cells led to a reduction in Cdk activities and insufficient hyperphosphorylation of pRb, resulting in inhibition of the cell cycle in the G0/G1 phase. 相似文献
9.
Renate Fingerhut F. Otto H. Oldiges J. Kiefer 《Radiation and environmental biophysics》1980,18(1):19-26
Summary Wild type diploid yeast, Saccharomyces cerevisiae strain 211, was subjected to 250 kV X-rays or 50° C heat treatment for 30 min or to a combination of both. X-ray exposure took place either in air or in nitrogen. Cell number, percentage of budding cells and cell cycle progression was followed for up to 12 h post irradiation. The distribution of cell cycle stages was determined by flow cytofluorometry. All treatments cause a retardation of cell division rate. Hyperthermia leads mainly to a lengthening of G1, whereas X-rays arrest the cells reversibly in G2. The effect of the combined treatment appears to be merely additive. No selective action of hyperthermia on hypoxic cells was found.Dedicated to Prof. Dr. A. Schraub on the occasion of his 70th birthday 相似文献
10.
Y. Carmazzi M. Iorio C. Armani S. Cianchetti F. Raggi T. Neri C. Cordazzo S. Petrini R. Vanacore F. Bogazzi P. Paggiaro A. Celi 《Cell proliferation》2012,45(6):545-556
Objectives
Clinical data suggest that heparin treatment improves survival of lung cancer patients, but the mechanisms involved are not fully understood. We investigated whether low molecular weight heparin nadroparin, directly affects lung cancer cell population growth in conventionally cultured cell lines.Materials and methods
A549 and CALU1 cells’ viability was assessed by MTT and trypan blue exclusion assays. Cell proliferation was assessed using 5‐bromo‐2‐deoxyuridine incorporation. Apoptosis and cell‐cycle distribution were analysed by flow cytometry; cyclin B1, Cdk1, p‐Cdk1 Cdc25C, p‐Cdc25C and p21 expressions were analysed by western blotting. mRNA levels were analysed by real time RT‐PCR.Results
Nadroparin inhibited cell proliferation by 30% in both cell lines; it affected the cell cycle in A549, but not in CALU‐1 cells, inducing arrest in the G2/M phase. Nadroparin in A549 culture inhibited cyclin B1, Cdk1, Cdc25C and p‐Cdc25C, while levels of p‐Cdk1 were elevated; p21 expression was not altered. Dalteparin caused a similar reduction in A549 cell population growth; however, it did not alter cyclin B1 expression as expected, based on previous reports. Fondaparinux caused minimal inhibition of A549 cell population growth and no effect on either cell cycle or cyclin B1 expression.Conclusions
Nadroparin inhibited proliferation of A549 cells by inducing G2/M phase cell‐cycle arrest that was dependent on the Cdc25C pathway, whereas CALU‐1 cell proliferation was halted by as yet not elucidated modes. 相似文献11.
Seven human cultured lymphoblastoid cell lines (CLL) were divided into two major groups based on studies of their cell cycle characteristics and surface Ig. CLL I (lines CL, MW, HH and TM) had generation times ranging from 25–40 hr, S phase times of 10–12 hr, G2 + M times of 6–8 hr, and demonstrated sharp differences between the percentage of SIg(+) cells in different phases of the cell cycle. Line TM was particularly discordant with the highest percentage of SIg(+) cells in G2 + M. CLL II (lines PS, JR and HT) demonstrated generation times ranging from 18–21 hr, S phase times of 7–10 hr and G2 + M phase times of 2 hr. In this second group, two of the three CLLs had no differences between cells taken from different points of the cell cycle. DNA synthesis and cell density could not be correlated with either of the above major parameters, i.e. cell cycle times or SIg expression. The results suggest that human CLLs fall into subgroups in which specific patterns of cellular and immune functions may predominate. 相似文献
12.
Threshold expression of cyclin E but not D type cyclins characterizes normal and tumour cells entering S phase 总被引:1,自引:0,他引:1
Complexes of cyclin-dependent kinases (cdk) and their partner cyclins drive the cell through the cell cycle, each such complex phosphorylating a distinct set of proteins at a particular check-point or phase of the cycle. Immunocytochemical detection of cyclins combined with measurement of cellular DNA content by flow cytometry makes it possible to relate expression of each of these proteins with the actual cell cycle position, without the necessity of cell synchronization. In the present study, we have investigated expression of E and D type cyclins in G1 cells and in cells entering S phase, in eight different human hematopoietic and solid tumour cell lines (two leukaemias, a lymphoma, three breast carcinomas, a colon carcinoma and a bladder transitional cell carcinoma) during their exponential phase of growth, as well as in normal mitogen stimulated lymphocytes. In all the cell types studied, the average level of D type cyclin expression was invariable throughout the cell cycle. A great intercellular variability, in particular of the G1 cell subpopulations, and the presence of a large fraction of G1, S and G2+ M cells that were cyclin D negative (20–40% in tumour cell lines and about 80% among lymphocytes), were other characteristic features of D type cyclin expression. In contrast to D type cyclins, the expression of cyclin E was discontinuous during the cycle, peaking at the time of cell entrance to S. Also, a well defined threshold in expression of cyclin E characterized cells that were entering S phase, and virtually no cyclin E negative cells were seen during the early portion of S phase. The data indicate that while cell entrance to S phase is unrelated to expression of D type cyclins (at the time of entrance), accumulation of cyclin E up to critical level is a prerequisite for initiation of DNA replication. The great intercellular variability in expression of D type cyclins and their invariant average level across the cell cycle suggest that these cyclins, in addition to their acknowledged function in promoting cell progression through mid- to late-G1 may have other role(s), related or unrelated to the cell cycle progression. The presence of a large number of D type cyclin negative cells in all phases of the cycle suggests that during exponential growth the cells may not express this protein and yet may traverse the cycle, including G1 phase. 相似文献
13.
Djerf Severinsson EA Trinks C Gréen H Abdiu A Hallbeck AL Stål O Walz TM 《Biochemical and biophysical research communications》2011,(3):563-568
The ErbB receptor family has been suggested to constitute a therapeutic target for tumor-specific treatment of malignant melanoma. Here we investigate the effect of the pan-ErbB tyrosine kinase inhibitor canertinib on cell growth and survival in human melanoma cells in vitro and in vivo. Canertinib significantly inhibited growth of cultured melanoma cells, RaH3 and RaH5, in a dose-dependent manner as determined by cell counting. Half-maximum growth inhibitory dose (IC50) was approximately 0.8 μM and by 5 μM both cell lines were completely growth-arrested within 72 h of treatment. Incubation of exponentially growing RaH3 and RaH5 with 1 μM canertinib accumulated the cells in the G1-phase of the cell cycle within 24 h of treatment without induction of apoptosis as determined by flow cytometry. Immunoblot analysis showed that 1 μM canertinib inhibited ErbB1-3 receptor phosphorylation with a concomitant decrease of Akt-, Erk1/2- and Stat3 activity in both cell lines. In contrast to the cytostatic effect observed at doses ?5 μM canertinib, higher concentrations induced apoptosis as demonstrated by the Annexin V method and Western blot analysis of PARP cleavage. Furthermore, canertinib significantly inhibited growth of RaH3 and RaH5 melanoma xenografts in nude mice. Pharmacological targeting of the ErbB receptors may prove successful in the treatment of patients with metastatic melanoma. 相似文献
14.
Background
Mitochondria exhibit a dynamic morphology in cells and their biogenesis and function are integrated with the nuclear cell cycle. In mitotic cells, the filamentous network structure of mitochondria takes on a fragmented form. To date, however, whether mitochondrial fusion activity is regulated in mitosis has yet to be elucidated.Findings
Here, we report that mitochondria were found to be fragmented in G2 phase prior to mitotic entry. Mitofusin 1 (Mfn1), a mitochondrial fusion protein, interacted with cyclin B1, and their interactions became stronger in G2/M phase. In addition, MARCH5, a mitochondrial E3 ubiquitin ligase, reduced Mfn1 levels and the MARCH5-mediated Mfn1 ubiquitylation were enhanced in G2/M phase.Conclusions
Mfn1 is degraded through the MARCH5-mediated ubiquitylation in G2/M phase and the cell cycle-dependent degradation of Mfn1 could be facilitated by interaction with cyclin B1/Cdk1 complexes.15.
Aims
The aim of the present study was to identify the potential therapeutic effects of BH3-mimetic gossypol on melanoma cells with acquired resistance to BRAF inhibitors.Main methods
The IC50 values of gossypol were determined using MTT assays in three melanoma cell lines with different resistances to BRAF inhibitor. The effects of gossypol on three melanoma cell lines were further examined by immunoblotting analysis, cell cycle analysis, flow cytometric apoptotic assay and autophagy assay. The functional role of autophagy in gossypol-induced growth inhibition was investigated using siRNA-mediated knockdown of Beclin-1.Key findings
Gossypol retained its efficacy in BRAF-V600E melanoma clones with acquired resistance to BRAF inhibitors through a mechanism independent of MEK–ERK inhibition. Gossypol caused G2/M arrest in both BRAF mutant A375P and A375P/Mdr cells with high expression of p21Cip1, regardless of their drug resistance. Interestingly, we determined that the lack of gossypol-induced mitotic arrest in BRAF-WT-harboring SK-MEL-2 cells was associated with a low level of p21Cip1 expression. In addition, gossypol preferentially induced autophagy and apoptosis in the gossypol-sensitive cells and not in the gossypol-resistant SK-MEL-2 cells. In particular, alleviation of autophagy by knockdown of Beclin-1 partially caused a resistance to gossypol-induced cell cycle arrest at G2/M in BRAF-V600E cells with a concomitant decreased induction of apoptosis.Significance
Taken together, these results suggest that gossypol may exhibit potential for the treatment of BRAF inhibitor-resistant tumors, but a functional p21Cip1 is a prerequisite for a positive response to its clinical application. 相似文献16.
17.
Qian Liu Bo Tao Guizhu Liu Guilin Chen Qian Zhu Ying Yu Yu Yu Hong Xiong 《The Journal of biological chemistry》2016,291(9):4779-4792
Multiple myeloma (MM) is a plasma cell malignancy without effective therapeutics. Thromboxane A2 (TxA2)/TxA2 receptor (T prostanoid receptor (TP)) modulates the progression of some carcinomas; however, its effects on MM cell proliferation remain unclear. In this study, we evaluated cyclooxygenase (COX) enzymes and downstream prostaglandin profiles in human myeloma cell lines RPMI-8226 and U-266 and analyzed the effects of COX-1/-2 inhibitors SC-560 and NS-398 on MM cell proliferation. Our observations implicate COX-2 as being involved in modulating cell proliferation. We further incubated MM cells with prostaglandin receptor antagonists or agonists and found that only the TP antagonist, SQ29548, suppressed MM cell proliferation. TP silencing and the TP agonist, U46619, further confirmed this finding. Moreover, SQ29548 and TP silencing promoted MM cell G2/M phase delay accompanied by reducing cyclin B1/cyclin-dependent kinase-1 (CDK1) mRNA and protein expression. Notably, cyclin B1 overexpression rescued MM cells from G2/M arrest. We also found that the TP agonist activated JNK and p38 MAPK phosphorylation, and inhibitors of JNK and p38 MAPK depressed U46619-induced proliferation and cyclin B1/CDK1 protein expression. In addition, SQ29548 and TP silencing led to the MM cell apoptotic rate increasing with improving caspase 3 activity. The knockdown of caspase 3 reversed the apoptotic rate. Taken together, our results suggest that TxA2/TP promotes MM cell proliferation by reducing cell delay at G2/M phase via elevating p38 MAPK/JNK-mediated cyclin B1/CDK1 expression and hindering cell apoptosis. The TP inhibitor has potential as a novel agent to target kinase cascades for MM therapy. 相似文献
18.
Accumulation patterns of mRNAs corresponding to histones H2A and H4, ribosomal protein genes rpL27 and rpL34, MAP kinase, cdc2 kinase and cyclin B were analyzed during growth-dormancy cycles in pea (Pisum sativum cv. Alaska) axillary buds. The level of each of these mRNAs was low in dormant buds on intact plants, increased when buds were stimulated to grow by decapitating the terminal bud, decreased when buds ceased growing and became dormant, and then increased when buds began to grow again. Flow cytometry was used to determine nuclear DNA content during these developmental transitions. Dormant buds contain G1 and G2 nuclei (about 3:1 ratio), but only low levels of S phase nuclei. It is hypothesized that cells in dormant buds are arrested at three points in the cell cycle, in mid-G1, at the G1/S boundary and near the S/G2 boundary. Based on the accumulation of histone H2A and H4 mRNAs, which are markers for S phase, cells arrested at the G1/S boundary enter S within one hour of decaptitation. The presence of a cell population arrested in mid-G1 is indicated by a second peak of histone mRNA accumulation 6 h after the first peak. Based on the accumulation of cyclin B mRNA, a marker for late G2 and mitosis, cells arrested at G1/S begin to divide between 12 and 18 h after decapitation. A small increase in the level of cyclin B mRNA at 6 h after decapitation may represent mitosis of the cells that had been arrested near the S/G2 boundary. Accumulation of MAP kinase, cdc2 kinase, rpL27 and rpL34 mRNAs are correlated with cell proliferation but not with a particular phase of the cell cycle. 相似文献
19.
20.
Grégory Gatouillat Emilie Balasse Débora Joseph‐Pietras Hamid Morjani Claudie Madoulet 《Journal of cellular biochemistry》2010,110(4):893-902
Resveratrol, a naturally occurring polyphenol, has been shown to possess chemopreventive activities. In this study, we show that resveratrol (0–500 µM) inhibits the growth of a doxorubicin‐resistant B16 melanoma cell subline (B16/DOX) (IC50 = 25 µM after 72 h, P < 0.05). This was accomplished by imposing an artificial checkpoint at the G1–S phase transition, as demonstrated by cell‐cycle analysis and down‐regulation of cyclin D1/cdk4 and increased of p53 expression level. The G1‐phase arrest of cell cycle in resveratrol‐treated (10–100 µM) B16/DOX cells was followed by the induction of apoptosis, which was revealed by pyknotic nuclei and fragmented DNA. Resveratrol also potentiated at subtoxic dose (25 µM for 24 h) doxorubicin cytotoxicity in the chemoresistant B16 melanoma (P < 0.01). When administered to mice, resveratrol (12.5 mg/kg) reduced the growth of an established B16/DOX melanoma and prolonged survival (32% compared to untreated mice). All these data support a potential use of resveratrol alone or in combination with other chemotherapeutic agents in the management of chemoresistant tumors. J. Cell. Biochem. 110: 893–902, 2010. © 2010 Wiley‐Liss, Inc. 相似文献