神经系统特异表达基因调控机理的研究进展

神经系统特异性基因正确的时空表达受细胞内外信号的调控,信号传导途径最终的靶位点是能结合特异转录因子的DNA序列.目前发现的决定神经系统基因特异性表达的顺式作用元件既有增强子,也有沉默子.它们可以特异性地增强基因在神经系统的表达,或特异性抑制基因在非神经系统的表达. 顺式元件要发挥这些作用,依赖于与其结合的反式因子,而这些反式因子又能与其他蛋白质或DNA序列发生互动, 通过协调作用,共同决定基因的时空表达顺序.     

Transcriptional Bursting Diversifies the Behaviour of a Toggle Switch: Hybrid Simulation of Stochastic Gene Expression

Hybrid models for gene expression combine stochastic and deterministic representations of the underlying biophysical mechanisms. According to one of the simplest hybrid formalisms, protein molecules are produced in randomly occurring bursts of a randomly distributed size while they are degraded deterministically. Here, we use this particular formalism to study two key regulatory motifs—the autoregulation loop and the toggle switch. The distribution of burst times is determined and used as a basis for the development of exact simulation algorithms for gene expression dynamics. For the autoregulation loop, the simulations are compared to an analytic solution of a master equation. Simulations of the toggle switch reveal a number of qualitatively distinct scenarios with implications for the modelling of cell-fate selection.     

HIV-1基因表达的转录调控

高效抗逆转录病毒治疗（HAART）可以有效地抑制人类免疫缺陷病毒Ⅰ型（HIV-1）的复制及血浆病毒载量,延缓发病进程,改善、提高患者的生活质量和存活时间。但是,一旦停止治疗就会导致血浆病毒血症迅速反弹,HIV-1以原病毒的形式在静息记忆CD4⁺T等细胞中的持续存在是清除HIV-1的一个障碍。HIV-1基因转录的激活与阻抑决定了受感染细胞进入产毒性感染或潜伏感染。本文从原病毒整合位置与转录干扰、细胞转录因子与HIV-1启动子相互作用招募RNA聚合酶起始转录、转录的表观遗传调控和反式激活因子Tat及其相关蛋白促进转录延伸等方面探讨了HIV-1原病毒转录调控机制。     

Circadian Yin-Yang Regulation and Its Manipulation to Globally Reprogram Gene Expression

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骨形成蛋白-2表达载体的构建及其转录活性测定

将骨形成蛋白-2(BMP-2)基因克隆入带HA标签的BMP-2表达载体中,得到带HA标签的重组质粒pGBKT7/HA-BMP-2,将该重组质粒转染酵母AH109、Y187细胞,Western印迹检测表明表达了与预期相对分子质量大小一致的BMP-2.BMP-2表达载体的成功构建为深入研究骨形成蛋白-2在促进骨痂生成过程中的分子机制及其生物学功能打下了基础.     

Transgenic and Transcriptional Studies on Neurosecretory Cell Gene Expression

1. Studies of the regulation of neurosecretory cell gene expression suffer from the lack of suitable cell lines. Two approaches have been used to overcome this deficit: transfection of neuropeptide genes into heterologous cell lines and generation of transgenic animals.2. Studies with heterologous cell lines have revealed the potential involvement of nuclear hormone receptors, POU proteins, and fos/jun/ATF family members in the regulation of the vasopressin and oxytocin genes. Although limited in their scope, these studies have contributed greatly to the dissection of basic properties of elements in the vasopressin and oxytocin gene promoters.3. Transgenic mice, and more recently rats, have been used to elucidate genomic regions governing cell specificity and physiological regulation of neurosecretory gene expression. The genes encoding the neuropeptides vasopressin and oxytocin have been used in many transgenic studies, due to the well-defined expression patterns and physiology of the endogenous neuropeptides. Cell-specific and physiologically regulated expression of these transgenes has been achieved, demonstrating the action of putative represser elements and regulation of the expression of one gene by sequences present in the other gene.4. Appropriate expression and translation of transgenes have resulted in the production of several useful systems. Expression of oncogene sequences in gonadotropin-releasing hormone neurons has allowed the development of cell lines from the resulting tumors, overproduction of corticotropin-releasing factor has produced animal models of anxiety and obesity, and directed ectopic expression of growth hormone has generated a potentially useful rat model of dwarfism. These and other animal models of human disease will provide important avenues for the development of therapeutic strategies.     

Stochastic Models of Gene Expression with Delayed Degradation

In many biochemical reactions occurring in living cells, number of various molecules might be low which results in significant stochastic fluctuations. In addition, most reactions are not instantaneous, there exist natural time delays in the evolution of cell states. It is a challenge to develop a systematic and rigorous treatment of stochastic dynamics with time delays and to investigate combined effects of stochasticity and delays in concrete models.We propose a new methodology to deal with time delays in biological systems and apply it to simple models of gene expression with delayed degradation. We show that time delay of protein degradation does not cause oscillations as it was recently argued. It follows from our rigorous analysis that one should look for different mechanisms responsible for oscillations observed in biological experiments.We develop a systematic analytical treatment of stochastic models of time delays. Specifically we take into account that some reactions, for example degradation, are consuming, that is: once molecules start to degrade they cannot be part in other degradation processes.We introduce an auxiliary stochastic process and calculate analytically the variance and the autocorrelation function of the number of protein molecules in stationary states in basic models of delayed protein degradation.     

家蚕BmST2基因的克隆与转录活性检测

通过生物信息学分析和生物学试验获得了家蚕糖转运蛋白基因BmST2(GenBank登录号:GQ871755),基因位于家蚕27号染色体,开放阅读框(ORF)长1398 bp,编码465个氨基酸,预测蛋白序列有典型的Sugar_tr结构域和11个疏水的跨膜结构域,与家蚕BmST1蛋白相似性和一致性分别达79%和64%,与登录号为EAT47626、EDS35465、EAA11457和EFA05337的同源蛋白相似性在50%以上。RT-PCR检测基因在5龄第3天家蚕幼虫的9种组织中转录活性,结果显示,BmST2基因除在脂肪体没有表达外,其他组织均有表达。最后成功构建了基因的酵母穿梭表达质粒pG-BKT7-BmST2。     

T细胞中IL-3基因表达调节的转录因子初探

主要利用凝胶迁移率试验和抗体超迁移试验,以ｈＩＬ－３基因５′侧翼含κＢ位点的序列为探针,探究ＮＦ－κＢ是否参与了ｈＩＬ－３基因的表达调节．结果表明,在Ｊｕｒｋａｔ细胞和人外周血Ｔ淋巴细胞中,都存在与此序列特异结合的可诱导蛋白;ＮＦ－κＢｐ６５亚基的单抗对ＤＮＡ－蛋白复合物的形成没有影响．这些结果揭示：正常细胞和肿瘤细胞中,确存在可特异识别ｈＩＬ－３基因５′侧翼的κＢ顺序的蛋白因子,而且该蛋白因子的表达是可诱导的;但ＮＦ－κＢ并未参与ＩＬ－３基因的表达调节．