p21对DNA聚合酶δ表达的抑制及其对MCF7细胞增殖和恶性表型的影响

细胞周期抑制因子p21能影响G1/S期转换和G2/M期进程，进而抑制细胞增殖．p21表达增高可以抑制多个DNA复制相关基因表达．DNA聚合酶δ是DNA复制中最为重要的复制酶，p21是否抑制它的表达，并通过这种作用影响细胞增殖及细胞恶性表型的变化，至今还没有报道．本研究观察到p21表达增强的MCF7p21细胞生长速率变慢，血清依赖性增强，细胞的锚定和非锚定依赖性增殖都受到抑制，表明p21表达增加对细胞增殖和细胞恶性表型的产生有重要作用．而Western blot检测发现在p21表达增高的MCF7p21细胞中，聚合酶δ（p125亚基）表达下降．p21高表达抑制POLD1启动子活性，这种抑制作用具有p21剂量依赖效应．这表明p21表达增高对细胞增殖的抑制和细胞恶性表型的影响可能是通过抑制在DNA复制中最重要的聚合酶δ（p125）的表达来实现的．这可能是p21对细胞增殖及恶性表型影响的一个新的调控机制．     

G1期细胞周期相关蛋白对POLD1基因启动子活性的调控

POLD1基因编码DNA聚合酶δ的催化亚基.然而作为最重要的复制蛋白,目前并不清楚其表达的细胞周期调控机制.研究中运用细胞周期同步化及荧光素酶报告基因测定了POLD1启动子在细胞周期不同时相的活性,结果显示启动子活性随着细胞周期进程而变化,在早S期最高.为进一步确定调控POLD1表达的细胞周期相关因子,应用不同质粒转染MCF7细胞,分别筛选得到稳定细胞系.荧光素酶实验表明增强p53或p21的表达,抑制CyclinE或CDK2的表达都能抑制POLD1启动子活性;而抑制CDK4或Cyclin D1的表达对启动子活性没有明显影响.瞬时共转染实验进一步验证Cyclin E或CDK2受到抑制后能够降低POLD1启动子活性.研究初步探讨了POLD1基因表达的细胞周期调控通路,进一步了解细胞周期因子对DNA复制体调控的复杂机制.     

Model and Algorithm of Transportation Problem on Network

Transportation problem on network needs to determine the freight quantity and the transportation route between supply point and demand point. Therefore, taken the uncertainty of freight supply and demand into account, a collaborative optimization model is formulated with transportation capacity constraint. In addition, a two-stage genetic algorithm （GA） is put forward. Herein, the first stage of this GA is adopted a priority-based encoding method for determining the supply and demand relationship between different points. Then supply and demand relationship which the supply and the demand are both greater than zero is a minimum cost flow （MCF） problem on network in the second stage. Aim at the purpose to solve MCF problem, a GA is employed. Moreover, this algorithm is suitable for balance and unbalance transportation on directed network or undirected network. At last, the model and algorithm are verified to be efficient by a numerical example.     

基于MCF5272嵌入式硬件平台的设计

本文介绍了基于MCF5272嵌入式系统硬件平台的结构设计,为今后嵌入式网络控制器的后继开发提供了一个嵌入式平台。     

ROZ与ATRA联合应用对MCF-7细胞诱导作用

研究PPART激动剂罗格列酮（ROZ）与全反式维甲酸（ATRA）联合应用诱导MCF-7细胞发生分化和凋亡的作用,阐述PPARγ激活后的抗肿瘤作用和机制．采用克隆原形成实验测定两化合物对MCF-7细胞存活率的影响;采用诱导分化实验测定两化合物对MCF-7细胞分化的影响;并进一步应用RT—PCR分析两化合物对MCF-7细胞相关基因表达的影响．集落形成实验显示,两化合物联合应用后,能明显抑制MCF-7细胞的生长．诱导分化实验表明,ROZ在低剂量时促进MCF-7细胞的分化,而随着剂量的增加,分化作用减弱,与ATRA联合应用后,同样在低剂量时促进MCF-7细胞分化,并且出现脂滴的细胞数增加,脂滴增大,在高剂量时,分化作用亦有所减弱。RT—PCR结果表明,在两化合物的作用下,MCF-7细胞中PPARγ的表达升高,并使MCF-7细胞中与凋亡相关基因的表达发生变化．ROZ与ATRA联合应用具有协同作用,激活PPARγ,抑制MCF-7细胞增殖,诱导MCF-7细胞发生分化．     

P53亚细胞定位变化对POLD1基因启动子活性的影响

POLD1基因编码DNA聚合酶δ(polδ)的催化亚基.体外实验表明p53能够抑制POLD1基因启动子活性.文中探讨p53是否在细胞内直接与POLD1启动子结合调节POLD1基因表达.在瞬时转染pEGFP-p53重组质粒的人乳腺癌MCF7细胞中,p53表达增强;RT-PCR结果显示POLD1基因mRNA表达受到抑制.染色体免疫共沉淀和荧光素酶报告基因实验证明p53在细胞内与POLD1启动子直接结合抑制其启动子活性.荧光显微镜观察发现EGFP-p53在G1期进入细胞核而在S期和G2期则被转运至细胞质.在稳定表达的pEGFP-p53细胞系中,细胞周期同步化后POLD1启动子活性在细胞周期各时相均处于较低水平.证明了细胞内p53高表达后通过直接与POLD1启动子结合而抑制POLD1基因表达,且这种抑制作用不受细胞周期进程的影响.     

抑癌基因p27在肿瘤细胞MCF7中的表达

抑癌基因p27是一个细胞周期依赖性激酶抑制子CKI(CDK inhibitor),对细胞周期起着负调控的作用,将p27基因克隆到表达载体pcDNA,转染到肿瘤细胞MCF7中,筛选到稳定表达株．p27基因的过量表达确实对肿瘤细胞的生长产生了抑制作用,并且引发了部分肿瘤细胞的凋亡．     

表皮生长因子效应评价细胞模型的建立

为了筛选表皮生长因子(EGF)信号通路的未知调控分子,利用人正常乳腺上皮细胞系MCF10A建立了EGF效应评价模型,包括细胞增殖、迁移以及细胞周期的进程等。结果显示,EGF能有效促进MCF10A细胞的增殖。饥饿同步化后,EGF能促进细胞从G1期进入S期,开始DNA的合成。此外,Transwell实验显示EGF能明显促进MCF10A细胞的迁移。     

Effects of PP4 suppression on the proliferation of MCF7 cells

In mammalian cells, reversible phosphorylation of protein substrates is a major mechanism for many cel-lular processes. Protein kinases and protein phosphata- ses, which catalyze protein phosphorylation and dephosphorylation respectively, together with th…     

A new chaotic function and its cryptographic usage

Wheeler pointed ouuailat the period of Matthews＇ chaotic function （MCF） is often too short to be suitable for crypto- graphic usage in the manner of computer statistics, but this statement was given only through digital computation. In this paper, we proved by theoretical and practical method that period exists in MCF and analyzed the underlying reason. With two chaotic functions working together we presented a modified MCF （MMCF） that is non-periodic. The simulation tests with reconstruction of phase space showed that our modified MCF is of no period. And we described how to implement a cryptographic usage with MMCF.