Mdm2生成速率调控的p53-Mdm2振子的全局动力学和稳定性

肿瘤抑制蛋白p53的动力学在一定程度上可以决定DNA损伤后的细胞命运.p53的动力学行为与p53信号通路中p53-Mdm2振子模块密切相关.然而,p53的负调控子Mdm2的生成速率的增加使其在一些癌细胞中过表达.因此探讨Mdm2生成速率对p53动力学的影响有重要意义.同时,PDCD5作为p53的激活子也调控p53的表达.因此,本文针对PDCD5调控的p53-Mdm2振子模型,通过分岔分析获得了Mdm2生成速率所调控的p53的单稳态、振荡以及单稳态与振荡共存的动力学行为,且稳定性通过能量面进行了分析.此外,噪声强度对p53动力学的稳定性有重要的影响.因此,针对p53的振荡行为,探讨了噪声强度对势垒高度和周期的影响.本文所获得的结果对理解DNA损伤后的p53信号通路调控起到一定的指导作用.     

DNA损伤致p53-Mdm2相互作用的动力学模型

最新实验结果表明，在受到各种辐射而引起DNA损伤后，在单体细胞和群体细胞情况下，细胞中的p53蛋白浓度表现为非衰减振荡和衰减振荡两种不同的动力学行为.通过研究p53-Mdm2负反馈回路的非线性动力学行为，分析了各种(特别是DNA损伤、p53和 Mdm2蛋白浓度三者之间)动力学关系，提出了一个能同时描述这两种不同动力学行为的非线性模型. 关键词： p53-Mdm2负反馈回路 非衰减振荡和衰减振荡 非线性动力学模型     

Nutlin-3a对p53-MDM2复合物稳定性影响

p53蛋白是一种与细胞周期停滞和细胞凋亡有关的蛋白质.在受到细胞压力或环境扰动后, p53促进下游多个靶基因的转录,介导肿瘤抑制. MDM2是主要的E3泛素连接酶,也是p53的负调控因子. MDM2可促进p53的泛素化和核输出,抑制p53的抑癌活性.因此MDM2对p53的负调控始终是肿瘤治疗中急切需要解决的问题. Nutlin-3a是被证明可以有效抑制p53-MDM2相互作用的小分子抑制剂.本文使用全原子分子动力学模拟,研究Nutlin-3a对p53-MDM2复合物的稳定性的影响.结果表明,通过引起p53和MDM2间Phe19-Gln72的氢键和Glu17-Lys94的盐桥发生的断裂, Nutlin-3a可以削弱p53和MDM2间的相互作用.我们的工作对Nutlin-3a小分子抑制剂的作用机制进行了说明,揭示了抗癌药物Nutlin-3a介导的p53-MDM2复合物亲和力降低的分子机制,并为针对p53蛋白的有效抗癌治疗提供了理论基础.     

DNA损伤致p53-Mdm2相互作用的非线性动力学模型(英文)

p53-Mdm2相互作用在DNA损伤的细胞响应方面起着非常重要的作用。最新实验结果表明,在受到各种辐射损伤而引起DNA损伤后,细胞中的p53蛋白浓度在单体细胞和群体细胞情况下,表现为非衰减振荡和衰减振荡两种不同的动力学行为。通过研究p53 -Mdm2负反馈回路的非线性动力学,分析了各种（特别是DNA损伤,p53和Mdm2浓度三者之间的）动力学关系,提出了一个能同时描述这两种不同动力学行为的非线性模型。 Exploring the nonlinear dynamics of the negative feedback loop composed of p53 and Mdm2 proteins, we propose a signal-response model to study the dynamical mechanism of the different oscillatory behaviors for the activities of p53 and Mdm2 proteins both in individual and population of cells. It is shown that the sustained and damped oscillatory dynamics could be described in a unified way when the dynamics of damage-derived signal is properly introduced.     

Hes1调控 AKT-MDM2-p53-PTEN通路的一种物理机制

基于Hill动力学与Michaelis-Menten方程，建立理论模型研究发状分裂相关增强子1(hairy and enhancer of split 1,Hes1)调控蛋白激酶B (Protein Kinase B,AKT)-鼠双微体2 (Murine Double Minute2,MDM2)-抗癌基因p53(p53)-第10号染色体缺失的磷酸酶及张力蛋白同源的基因(Phosphatase and tensin homolog deleted on chromosome ten,PTEN)通路的一种物理机制.研究发现，Hes1通过与PTEN结合抑制PTEN表达，并调控AKT信号.表明了Hes1蛋白的合成，以及Hes1与PTEN相互作用调控AKTMDM2-p53-PTEN通路信号，将会有效地控制细胞结果 . Hes1作为AKT-MDM2-p53-PTEN信号通路中上游调节的重要因素，还可以在一定程度上通过影响p53蛋白功能，改变p53对肿瘤的抑制性.理论结果可用于预测Notch通路信号异常诱导的致癌性，并进一步揭示了Notch信号通路影响细胞AKT-MDM2-p53-PTEN通路的激活...     

VPRBP 蛋白与Abl 激酶诱发、抑制前列腺癌的 一种物理机制

在本文基于Hill动力学与Michaelis-Menten方程,建立理论模型研究VPRBP蛋白与Abl激酶诱发、抑制前列腺癌的一种物理机制.研究发现,DNA损伤使得ATM(共济失调毛细血管扩张症突变)很快激活,并激活上调p53蛋白表达,DNA损伤的后续破坏会在很大程度上通过p53表达上调而被抑制. VPRBP通过上调MDM2蛋白的激活水平,使得p53表达水平异常,进而无法正常抑制前列腺癌的发生发展.通过考察Abl在前列腺癌进程中的作用发现,Abl使得AKT的表达水平下调,由于Abl对AKT的抑制作用,致使在AKT信号通路中MDM2表达水平受到抑制,进而稳定p53表达.由此表明了,过少的Abl对AKT的抑制程度减弱,不仅使得细胞代谢出现紊乱,而且还会促使p53正常的周期表达水平异常,对DNA损伤诱发的肿瘤抑制性减弱,进而促进前列腺癌的发生发展.基于本文模型,可以预测VPRBP与Abl作为诱发、抑制前列腺癌的调节剂对现有和潜在的抗癌治疗较为敏感. VPRBP与Abl在诱发、抑制前列腺癌过程中的时滞效应,导致信号通路中p53与PTEN蓄积量增多、AKT蓄积量减少,以及Plk1周期振荡相位转移...     

酵母蛋白质网络的动力学性质

蛋白质-蛋白质、蛋白质-DNA相互作用网络决定了细胞中各种关键功能的执行．基于芽殖酵母(budding yeast saccharomyces cerevisiae)的蛋白质-蛋白质相互作用网络数据和相关的实验文献，我们建立了调控细胞周期和生命周期(cell cycle and life cycle)的蛋白质网络，并利用离散模型研究了该网络的动力学性质，研究表明：细胞周期网络的动力学性质具有很强的稳定性，约94％的蛋白质初态将演化到对应于生物学G1基态的稳定态，使其成为惟一的全局吸引点；同时，绝大多数的初态的演化路径都通过由G1激发态到G1基态的细胞周期演化路径，使细胞周期路径成为全局性的“吸引”路径。     

UV-B诱导的水稻DNA损伤和修复研究

利用单克隆抗体ELISA,研究了UV-B对水稻DNA中CPDs和6-4PPs的诱导形成,并证实了水稻幼苗中DNA损伤的光修复和暗修复的存在.经UV-B处理的水稻幼苗,DNA中CPDs和6-4PPs的积累随UV-B处理时间的增加而上升.水稻幼苗DNA损伤的暗修复能力较低,24h内仅修复约20～30%.与暗修复相比,DNA损伤的光修复进程较快;CPDs的光修复在20min内可修复50%;而6-4PPs的光修复需要1h才能完成50%修复.以上结果表明,UV-B诱导的水稻DNA损伤的修复以光修复为主,且CPDs和6-4PPs的修复活性与其它植物存在差异.     

茶多酚对6-OHDA诱导的SH-SY5Y细胞凋亡的保护作用

茶多酚在体内具有广泛的生物活性和药理作用,有助于预防与氧化应激相关的疾病,比如癌症,心血管疾病,神经退行性疾病和衰老. 氧化应激参与了帕金森病（PD）的病理进程. 活性氧在PD的发病机制中发挥了重要的作用,氧自由基直接损伤细胞膜引起脂质过氧化,损伤蛋白质和各种功能酶引起蛋白质沉淀,诱导促凋亡因子的表达,损伤DNA,最终导致了细胞的凋亡. 然而,关于茶多酚对PD的预防和治疗作用目前还不清楚. 本文应用氧化应激诱导的PD病理细胞模型,评价了茶多酚的神经保护作用. 结果表明茶多酚这类植物天然抗氧化剂对氧化应激诱导的细胞凋亡具有明确的抑制作用. 实验中我们选择了6-OHDA诱导的SH-SY5Y细胞作为细胞模型, 运用了MTT、流式细胞术、荧光显微成相, 竞争性ELISA和蛋白质杂交等方法研究了SH-SY5Y细胞的凋亡特性. 结果表明,6-OHDA对SH-SY5Y有时间-浓度依赖性细胞毒性,100 μmol/L 6-OHDA处理24 h,细胞活力减少50 %,同时伴随着活性氧增加（用ＥＳR）,线粒体膜电位降低,细胞内钙离子和一氧化氮增加,nNOS和iNOS表达量上升及蛋白结合的硝基酪氨酸水平升高. 单独茶多酚处理对细胞没有太大的影响,而茶多酚预处理可显著降低6-OHDA所产生的细胞毒性. 溶液实验证明,茶多酚对6-OHDA的自氧化有浓度-时间依赖性抑制作用（用ＥＳＲ）. 本研究表明茶多酚可能是通过活性氧-一氧化氮途径,减少过氧亚硝基的生成来对6-OHDA诱导的细胞凋亡表现保护作用的. 本文的实验结果提示茶多酚在治疗PD等慢性神经退行性疾病上可能是一种有着潜在疗效的药物.     

重离子对人胃癌细胞DNA错配修复基因MSH2 表达的影响

采用高传能线密度(LET) 重离子辐照人胃癌SGC7901 细胞,应用流式细胞技术、蛋白质印迹法(Western blot) 及反转录聚合酶链式反应(RT-PCR) 观察重离子诱导人胃癌SGC7901 细胞周期、凋亡和MSH2 表达状况。结果表明: 与对照组相比,SGC7901 细胞在辐射后72 h G2/M 期所占细胞比率(33.26±0.08) 和凋亡率(24.16±0.64) 均达到峰值,且呈时间依赖性增加;经重离子照射后,DNA错配修复基因MSH2 mRNA 和蛋白表达水平在6 h 最高。结果提示:重离子在体外诱导SGC7901 细胞周期阻滞和凋亡,且具有显著的时间依赖性效应;重离子在一定剂量和时间下,诱导了SGC7901 细胞MSH2 基因表达。DNA错配修复基因MSH2 可能参与了重离子辐照诱导胃癌细胞DNA损伤的修复应答。Human gastric cancer cell SGC7901 were irradiated with high linear energy transfer (LET) carbon ion. Apoptotic cells after irradiation were analyzed by flow cytometry and expression of MSH2 genes in the irradiated cells was detected by western blot and RT-PCR assay. Compared with the control group, we found that the number of G2/M (33.26±0.08) or apoptosis (24.16±0.64) of SGC7901 cells reached a maximum after irradiation at 72 h in a dose dependent manner. And heavy ion irradiation efficiently up-regulated the expression of MSH2 gene at 4.0 Gy after being irradiated 6 h. These results imply that heavy ion beam could induce cell apoptosis and cell cycle arrest in time-dependent manners. Furthermore, expression of MSH2 genes activated by carbon ion irradiation suggests that DNA mismatch repair gene MSH2 might be involved in DNA repair pathways.     

Spatio-temporal analysis of DNA damage repair using the X-ray microbeam

Cellular response to radiation damage is made by a complex network of pathways and feedback loops whose spatiotemporal organization is still unclear despite its decisive role in determining the fate of the damaged cell. The single-cell approach and the high spatial resolution offered by microbeams provide the perfect tool to study and quantify the dynamic processes associated with the induction and repair of DNA damage. The soft X-ray microbeam has been used to follow the development of radiation induced foci in live cells by monitoring their size and intensity as a function of dose and time using yellow fluorescent protein (YFP) tagging techniques. Preliminary data indicate a delayed and linear rising of the intensity signal indicating a slow kinetic for the accumulation of DNA repair protein 53BP1. A slow and limited foci diffusion has also been observed. Further investigations are required to assess whatever such diffusion is consistent with a random walk pattern or if it is the result of a more structured lesion processing phenomenon. In conclusion, our data indicates that the use of microbeams coupled to live cell microscopy represent a sophisticated approach for visualizing and quantifying the dynamics changes of DNA proteins at the damaged sites.     

Kick-starting the cell cycle: From growth-factor stimulation to initiation of DNA replication

The essential genes, proteins and associated regulatory networks involved in the entry into the mammalian cell cycle are identified, from activation of growth-factor receptors to intracellular signal transduction pathways that impinge on the cell cycle machinery and ultimately on the initiation of DNA replication. Signaling pathways mediated by the oncoproteins Ras and Myc induce the activation of cyclin-dependent kinases CDK4 and CDK2, and the assembly and firing of pre-replication complexes require a collaboration among E2F, CDK2, and Cdc7 kinase. A proposed core mechanism of the restriction point, the major checkpoint prior to commitment to DNA synthesis, involves cyclin E/CDK2, the phosphatase Cdc25A, and the CDK inhibitor p27Kip1. (c) 2001 American Institute of Physics.     

Radiation-induced robust oscillation [2mm]and non-Gaussian fluctuation

There have been many recent studies devoted to the consequences of stochasticity in protein circuitry. Stress conditions, including DNA damage, hypoxia, heat shock, nutrient deprivation, and oncogene activation, can result in the activation and accumulation of p53. Several experimental studies show that oscillations can be induced by DNA damage following nuclear irradiation. To explore the underlying dynamical features and the role of stochasticity, we discuss the oscillatory dynamics in the well-studied regulatory network motif. The fluctuations around the fixed point of a delayed system are Gaussian in the limit of sufficiently weak delayed feedback, and remain Gaussian along a limit cycle when viewed tangential to the trajectory. The experimental results are recapitulated in this study. We illustrate several features of the p53 activities, which are robust when the parameters change. Furthermore, the distribution in protein abundance can be characterized by its non-Gaussian nature.     

Balanced biosynthesis and trigger threshold resulting in a double adder mechanism of cell size control

How cells accomplish cell size homeostasis is a fascinating topic, and several cell size regulation mechanisms were proposed: timer, sizer, and adder. Recently the adder model has received a great deal of attention. Adder property was also found in the DNA replication cycle. This paper aims to explain the adder phenomenon both in the division-centric picture and replication-centric picture at the molecular level. We established a self-replication model, and the system reached a steady state quickly based on evolution rules. We collected tens of thousands of cells in the same trajectory and calculated the Pearson correlation coefficient between biological variables to decide which regulatory mechanism was adopted by cells. Our simulation results confirmed the double-adder mechanism. Chromosome replication initiation and cell division control are independent and regulated by respective proteins.Cell size homeostasis originates from division control and has nothing to do with replication initiation control. At a slow growth rate, the deviation from adder toward sizer comes from a significant division protein degradation rate when division protein is auto-inhibited. Our results indicated the two necessary conditions in the double-adder mechanism: one is balanced biosynthesis, and the other is that there is a protein trigger threshold to inspire DNA replication initiation and cell division. Our results give insight to the regulatory mechanism of cell size and instructive to synthetic biology.     

p73变异体研究现状及其在肿瘤放疗中的应用前景

p73基因是p53抑癌基因家族的新成员。 p73有两组蛋白异构体: TAp73和DNp73。 TAp73具有诱导细胞周期停滞和细胞凋亡的能力, 而DNp73却有与之相反的能力, 具有肿瘤促进作用。 对p73基因两面性的特点及研究进展作一综述。 最后结合重离子治疗肿瘤, 探讨了p73联合重离子治疗的新思路。 p73 was the first identified homologue of the tumor suppressor gene, p53. p73 has two groups of protein isoforms: TAp73 and DNp73. TAp73 can induce cell cycle arrest, resulting in the ability of apoptosis, however DNp73 has antagonistic property of a tumor promoting effect. In this paper, the dual roles of p73 gene and its research progress was reviewed. Finally, combined with heavy ion treatment of tumor, we explored some new ideas of p73 heavy ion joint therapy.