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ABSTRACT: Micronuclei are closely related to DNA damage. The presence of micronuclei in mammalian cells is a common phenomenon post ionizing radiation. The level of micronucleation in tumor cells has been used to predict prognosis after radiotherapy in many cancers. In order to understand how irradiation-induced micronuclei affect cell fate, we performed extensive long-term live cell imaging on X-irradiated nasopharyngeal carcinoma (NPC) cells. To visualize the dynamics of micronuclei more clearly, chromosomes were stably labeled with red fluorescent protein (RFP) by targeting to human histone H2B. Initially, significantly more micronuclei were observed in radiosensitive cells than in radioresistant cells post irradiation. Additionally, cells with micronuclei were found to be more likely to die or undergo cell cycle arrest when compared with micronucleus-free cells after irradiation, and the more micronuclei the cells contained the more likely they would die or undergo arrest. Moreover, micronucleated cells showed predisposition to produce daughter cells with micronuclei through chromosome lagging. Fluorescence in situ hybridization using human pan-centromeric probes revealed that about 70% of these micronuclei and lagging chromosomes did not contain centromeric signals. Finally, DNA damage was more severe and p38 stress kinase activity was higher in micronucleated cells than in micronucleus-free cells as shown by phospho-H2AX and phospho-p38 immunofluorescence staining. Altogether, our observations indicated that the presence of micronuclei coupled with activated DNA damage response could compromise the proliferation capacity of irradiated cells, providing the evidence and justification for using micronucleus index as a valuable biomarker of radiosensitivity.
DNA repair 06/2011; 10(6):629-38. · 4.20 Impact Factor
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ABSTRACT: Although micronuclei (MNi) have been extensively used to evaluate genotoxic effects and chromosome instability, the most basic issue regarding their formation was not completely addressed until recently, due to limitations of traditional experimental methods. The development of live-cell imaging, combined with genetically engineered chromosome labelling techniques makes it possible to investigate the origin of a micronucleus in a single cell in a real-time and high-throughput manner. Here, we review all the available studies on the origins of MNi in live cells and discuss novel findings based on this recently emerged methodology. Some unsolved questions on MNi formation and limitations of live-cell imaging in the investigation of MNi have also been discussed.
Mutagenesis 01/2011; 26(1):133-8. · 3.18 Impact Factor
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ABSTRACT: p53 abnormality and aneuploidy often coexist in human tumors, and tetraploidy is considered as an intermediate between normal diploidy and aneuploidy. The purpose of this study was to investigate whether and how p53 influences the transformation from tetraploidy to aneuploidy.
Live cell imaging was performed to determine the fates and mitotic behaviors of several human and mouse tetraploid cells with different p53 status, and centrosome and spindle immunostaining was used to investigate centrosome behaviors. We found that p53 dominant-negative mutation, point mutation, or knockout led to a 2∼ 33-fold increase of multipolar mitosis in N/TERT1, 3T3 and mouse embryonic fibroblasts (MEFs), while mitotic entry and cell death were not significantly affected. In p53-/- tetraploid MEFs, the ability of centrosome clustering was compromised, while centrosome inactivation was not affected. Suppression of RhoA/ROCK activity by specific inhibitors in p53-/- tetraploid MEFs enhanced centrosome clustering, decreased multipolar mitosis from 38% to 20% and 16% for RhoA and ROCK, respectively, while expression of constitutively active RhoA in p53+/+ tetraploid 3T3 cells increased the frequency of multipolar mitosis from 15% to 35%.
p53 could not prevent tetraploid cells entering mitosis or induce tetraploid cell death. However, p53 abnormality impaired centrosome clustering and lead to multipolar mitosis in tetraploid cells by modulating the RhoA/ROCK signaling pathway.
PLoS ONE 01/2011; 6(11):e27304. · 4.09 Impact Factor
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ABSTRACT: Nucleophosmin/B23, an abundant nucleolar protein, plays multiple roles in cell growth and proliferation, and yet, little has been studied about its function in regulating dynamics of microtubules. Here, we report that B23 directly interacts with Eg5, a member of the kinesin family, in the cytosol. The DNA/RNA binding domain of B23 and the motor domain of Eg5 were found to be involved in their interaction. Both in vivo and in vitro evidences showed that B23 acts as an upstream regulator of Eg5 in promoting microtubule polymerization. Moreover, we further demonstrated that B23 regulates microtubule dynamics by directly inhibiting Eg5 ATPase activity.
Journal of Biological Chemistry 06/2010; 285(25):19060-7. · 4.77 Impact Factor
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Helvetica Chimica Acta 06/2010; 93(6):1156 - 1161. · 1.48 Impact Factor
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ABSTRACT: Although micronuclei (MNi) are extensively used to evaluate genotoxic effects and chromosome instability, the most basic issue regarding their origins has not been completely addressed due to limitations of traditional methods. Recently, long-term live cell imaging was developed to monitor the dynamics of single cell in a real-time and high-throughput manner. In the present study, this state-of-the-art technique was employed to examine spontaneous micronucleus (MN) formation in untreated HeLa cells. We demonstrate that spontaneous MNi are derived from incorrectly aligned chromosomes in metaphase (displaced chromosomes, DCs), lagging chromosomes (LCs) and broken chromosome bridges (CBs) in later mitotic stages, but not nuclear buds in S phase. However, most of bipolar mitoses with DCs (91.29%), LCs (73.11%) and broken CBs (88.93%) did not give rise to MNi. Our data also show directly, for the first time, that MNi could originate spontaneously from (1) MNi already presented in the mother cells; (2) nuclear fragments that appeared during mitosis with CB; and (3) chromosomes being extruded into a minicell which fused with one of the daughter cells later. Quantitatively, most of MNi originated from LCs (63.66%), DCs (10.97%) and broken CBs (9.25%). Taken together, these direct evidences show that there are multiple origins for spontaneously arising MNi in HeLa cells and each mechanism contributes to overall MN formation to different extents.
Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis 10/2008; 646(1-2):41-9. · 2.85 Impact Factor
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Annalen der Chemie und Pharmacie 06/2006; 2006(16):3730 - 3737. · 3.10 Impact Factor
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ABSTRACT: The melt blending method was applied to prepare ternary composites of polypropylene (PP)/organic-rectorite (OREC)/polyethylene-octene elastomer (POE) at constant content of 2 phr (parts per hundred PP) of OREC and 5, 10, 15 phr of POE (named PRE25, PRE210, and PRE215, separately) via twin-screw extruder. At the same time the binary composites of OREC/PP at 2 phr loading of OREC, named PR2 were prepared in order to investigate effects of OREC and POE on rheology and crystallization properties of composites. The rheology was characterized on capillary rheometer, nonisothermal crystallization kinetics on differential scanning calorimetry (DSC), and thermal stability properties on thermogravimetric analysis (TG). It is found that melting PR2 and PRE systems conform to the law of Non-Newton and shear-thinning behavior is observed for both systems. The apparent viscosity of the melt decreases with the increase of POE loadings. The crystallization halftime (t1/2) of PRE is shorter, the rate constant Zc larger, which indicates OREC and POE has the heterogeneous nucleation effect and the crystallization rate of PP was increased. The enthalpy of PRE is lower than that of PR2 and pure PP at the same conditions, which shows that the relative crystallinity of PRE composites are reduced. TG curves show that the ternary systems have higher thermal stability in contrast with pure PP. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1915–1921, 2005
Journal of Applied Polymer Science 06/2005; 97(5):1915 - 1921. · 1.29 Impact Factor
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04/2002;
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ABSTRACT: Net protein ratio (NPR), predicted-protein efficiency ratio (P-PER), relative NPR (RNPR), and corrected RNPR (CRNPR) of thermally processed red kidney beans were estimated in rats and compared to invitro protein digestibility-corrected amino acid score (AASIVDP), and computed-protein efficiency ratio (C-PER). Thermal processing had a significant effect on protein intake, NPR, P-PER and CRNPR values of beans. Changes in protein intake suggest that heat processing had an effect on the palatability of the beans. Home-cooked beans and commercially canned beans had higher NPR values than beans autoclaved at 128°C for 20 min, while beans autoclaved at 121°C for 10–90 min had intermediate values. High correlation coefficients between P-PER and C-PER, CRNPR and C-PER, and CRNPR and AASIVDP (r=0·990, 0·992 and 0·960, respectively, P<0·001) were observed.
Journal of the Science of Food and Agriculture 03/1999; 71(4):491 - 495. · 1.44 Impact Factor
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ABSTRACT: Thermal effect on availability of individual amino acids (AIAA) of red kidney beans was evaluated. Sulfur amino acids (SAA), methionine and cystine (Met + Cys), are the limiting amino acids (AA) and have the lowest availability among the AAs in nine treatments. The availability of SAA (ASAA) ranged from −18.6% in raw beans to 39.8−68.0% in thermally processed beans. Autoclaving at 121 °C for 10−90 min gradually reduced ASAA values. The mean availability for each AA (MAEAA) is the average of the AIAA values for the same AA. MAEAA values ranged from 82.1% (arginine) to 50.4% (Met + Cys). The mean availability in each treatment (MAET) is the average of the AIAA values in the same treatment. The difference between MAET and true digestibility of protein (TDP) was less than 7%. However, the differences between ASAA and TDP (16−37%) and between ASAA and MAET (14−30%) were large. The ASAA-corrected amino acid score (AASASAA) for raw beans was negative (−29.4%) and ranged from 61.8 to 42.1% for thermally processed beans. From a comparison among the protein quality indexes, AASASAA is the preferred method to evaluate protein quality of beans. Keywords: Amino acid availability; availability-corrected amino acid score; red kidney beans
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