Ran结合蛋白RanBP1的生物学功能及研究进展

RanBP1是RanGTPase循环过程中的关键调节因子,参与细胞核质运输、中心体的装配、微管的聚合、纺锤体的组装以及核膜的重建等.RanBP1表达量异常影响染色体的正常分离,使细胞分裂异常,导致细胞凋亡,甚至引起肿瘤发生.研究证实在多种肿瘤组织细胞中RanBP1表达量异常增高.本文综述了RanBP1氨基酸序列信息以及晶体结构信息,对RanBP1的生物功能以及在不同肿瘤中的表达情况进行了总结分析,探讨了RanBP1作为抗肿瘤药物潜在靶标的可能性.     

细胞骨架在减数分裂中作用的研究

细胞骨架是存在于真核细胞中的一种动态网络结构,可调控细胞形态、植物细胞壁的发育,同时在构成细胞质、运输细胞成分、驱使细胞运动、完成有丝分裂和减数分裂等方面均发挥着重要作用.减数分裂是生物细胞中染色体数目减半的一种特殊的细胞分裂方式,减数分裂对于生物体有性生殖是至关重要的,既有效获得了父母双方的遗传物质,以保持后代的遗传性,又可以增加更多的变异机会,确保生物的多样性,增强生物适应环境变化的能力.因此减数分裂一直以来是人们研究的热点问题.本文综述了纺锤体微管和成膜体微管在减数分裂过程中的组装及作用以及微丝骨架在细胞减数分裂各个时期可能的作用,为继续研究细胞骨架在减数分裂过程中的作用提供一定的理论依据.     

蛋白质亚细胞定位预测研究进展

蛋白质的功能与其在细胞中的定位有着密切的联系,新合成的蛋白质必须处于适当的亚细胞位置才能正确的行使其功能．预测蛋白质的亚细胞定位,在确定一个未知蛋白质的功能,了解蛋白质相互作用等方面有着重要的意义．机器学习方法在蛋白质亚细胞定位研究中扮演着一个重要的角色．笔者从数据集的构建、蛋白质序列特征提取方法、蛋白质亚细胞定位预测算法以及预测算法的性能评估等四方面总结了过去十几年间机器学习方法在蛋白质亚细胞定位研究中的应用情况,系统阐述了蛋白质亚细胞定位预测研究的进展．     

浅析贵广铁路调整为客运专线的必要性

贵广铁路原规划是以客为主兼顾货运的连接西南、华南地区间的快速铁路通道。随着2008年《中长期铁路网规划》的调整,周边路网构成以及区域运输需求都发生较大变化,有必要对其功能以及在路网中的地位和作用重新进行研究和定位。文章从运输需求、路网布局、相关通道运输能力以及运输服务质量等方面,分析了区域路网构成和标准的重大变化对贵广铁路功能定位所产生的影响,阐述了贵广铁路调整为客运专线的必要性。     

高等植物发育过程中细胞式样的形成

高等植物发育过程中，植物准确地控制细胞分裂，细胞形态，细胞数目以及细胞命运。本文简要地介绍了近年来这方面研究取得的重要进展。     

线粒体的遗传与胞内运输

细胞分裂时,母细胞将细胞器分配到子细胞是极为重要的过程,线粒体也不例外.因为线粒体的特殊性,即半自主性及母源遗传,使其在分配时与其他细胞器有所不同.该文前半部分主要介绍调节线粒体分配的不同机制,这些机制通过线粒体融合与分裂,细胞器运输等方式确保将有功能的线粒体传递给后代,后半部分综述了胚胎发育过程中线粒体母源遗传机制及遗传瓶颈效应.     

动力蛋白轻链亚基LC8在人细胞内的亚细胞定位

动力蛋白是活跃于微管骨架上行使负向运输功能的分子马达.从人类B淋巴细胞cDNA文库中克隆得到动力蛋白轻链亚基的基因LC8,将该基因插入表达绿色荧光蛋白的载体pEGFP-C3,获得的重组DNA成功在两种人源细胞内表达.通过荧光实验对GFP-LC8亚细胞定位进行分析,确定GFP-LC8是典型细胞浆定位,主要分布在细胞外周区和微管组织中心附近.当用药物nocodazole处理细胞使微管解聚时,GFP-LC8的定位发生改变.表明融合蛋白可正确指示LC8的细胞定位,可用于进一步研究病毒感染后的胞内事件.     

果蝇锌离子转运蛋白Catsup亚细胞定位分析

Catsup是果蝇体内一个功能重要的基因,其突变会导致体内多巴胺含量过高,引起果蝇致死及生殖障碍.绿色荧光蛋白(green fluorescent protein,GFP)在确定蛋白的亚细胞定位进而在研究蛋白功能方面起着重要的作用.为了探索Catsup的亚细胞定位进而能够更好地研究Catsup的功能,文章利用基因工程技术和生物学方法,聚合酶链式反应(polymerase chain reaction,PCR)扩增Catsup基因全长,与GFP一起连接至pUAST质粒,构建载体pUAST-Catsup-GFP,通过显微注射技术导入果蝇,获得UAS-Catsup-GFP转基因果蝇.通过克隆验证了转基因果蝇构建成功.利用该果蝇进行Catsup的亚细胞定位,确定其定位在高尔基体上,为进一步研究该基因的功能奠定基础.     

拟南芥Patellin2相互作用蛋白的筛选及鉴定

Patellin 2(PATL2)蛋白是具有SEC14蛋白结构域的脂质转移蛋白,定位于细胞分裂后期的细胞板上,在细胞分裂过程中发挥重要的作用.同时,PATL2蛋白还受到植物激素和环境变化的调控,说明PATL2可能在植物激素和环境变化的调控下参与细胞分裂过程.为了深入了解PATL2蛋白的生物学功能,研究PATL2蛋白发挥作用的分子生物学机制,我们分析了它在植物体内的表达特点和与之相互作用的蛋白.我们通过免疫共沉淀与液相色谱-串联质谱法(LC-MS/MS)分析了过表达PATL2的转基因植株,并获得了多个可能与PATL2相互作用的蛋白,其中一个是细胞周期蛋白依赖性激酶CDKB2;2.通过观察PATL2启动子驱动的GUS报告基因在植物中的表达,发现PATL2基因在叶片、花瓣、花粉中广泛表达,但在角果中的表达非常有限,仅存在于角果的两端,这与已报道的CDKB2;2的组织分布部分相同.同时,烟草叶表皮细胞瞬时表达结果表明PATL2和CDKB2;2能够共定位于烟草叶表皮细胞的细胞膜和细胞质中.体外pull-down实验和双分子荧光互补实验(BiFC)实验分别确定了PATL2和CDKB2;2在植物体外和植物体内的相互作用.     

菘蓝离体培养过程中愈伤组织和再生芽发生的细胞组织学观察

对菘蓝子叶和下胚轴在离体培养过程中的细胞分裂、分化以及器官发生进行了细胞组织学观察.研究结果 表明:培养2～5d,切口处及维管束薄壁细胞均开始脱分化,恢复分裂能力形成愈伤组织,愈伤组织表层细胞启 动分化形成芽原基.2种外植体不定芽的起源方式均为外起源.     

Structural insights into yeast septin organization from polarized fluorescence microscopy

Septins are polymerizing GTPases that function in cortical organization and cell division. In Saccharomyces cerevisiae they localize at the isthmus between the mother and the daughter cells, where they undergo a transition from a non-dynamic hourglass-shaped assembly to two separate rings, at the onset of cytokinesis. Septins form filaments as pure protein and in vivo, but the filament organization within the hourglass and ring structures is controversial. Here, we use polarized fluorescence microscopy of orientationally constrained green fluorescent protein to determine septin filament organization and dynamics in living yeast. We found that the hourglass is made of filaments aligned along the yeast bud neck. During the transition from hourglass to rings the filaments rotate through 90 degrees in the membrane plane and become circumferential. These data resolve a long-standing controversy in the field and provide strong evidence that septins have a mechanical function in cell division.     

Functional genomic analysis of cell division in C. elegans using RNAi of genes on chromosome III

Genome sequencing projects generate a wealth of information; however, the ultimate goal of such projects is to accelerate the identification of the biological function of genes. This creates a need for comprehensive studies to fill the gap between sequence and function. Here we report the results of a functional genomic screen to identify genes required for cell division in Caenorhabditis elegans. We inhibited the expression of approximately 96% of the approximately 2,300 predicted open reading frames on chromosome III using RNA-mediated interference (RNAi). By using an in vivo time-lapse differential interference contrast microscopy assay, we identified 133 genes (approximately 6%) necessary for distinct cellular processes in early embryos. Our results indicate that these genes represent most of the genes on chromosome III that are required for proper cell division in C. elegans embryos. The complete data set, including sample time-lapse recordings, has been deposited in an open access database. We found that approximately 47% of the genes associated with a differential interference contrast phenotype have clear orthologues in other eukaryotes, indicating that this screen provides putative gene functions for other species as well.     

A family of related ATP-binding subunits coupled to many distinct biological processes in bacteria

Many biological processes are coupled to ATP hydrolysis. We describe here a class of closely related ATP-binding proteins, from several bacterial species, which are associated with a variety of cellular functions including membrane transport, cell division, nodulation in Rhizobium and haemolysin export. These proteins comprise a family of structurally and functionally related subunits which share a common evolutionary origin, bind ATP and probably serve to couple ATP hydrolysis to each of these biological processes. This finding suggests a specific role for ATP in cell division, nodulation during nitrogen fixation and protein export, and allows us to assign a probable function to one of the protein components from each of these systems.     

Epistatic gene interactions in the control of division in fission yeast

THERE is currently much interest in the mechanism which controls the timing of cell division. Certain features of the control have been found to be common to a variety of eukaryotes. In particular, the importance of cell size as a parameter affecting cell cycle progress has been reported for mammalian cells(1,2) and for several single-celled eukaryotes(3-6). Another feature common to several systems is that growth conditions have a direct effect on the timing of division cycle events(7-9), and on cell size(9,10). In the fission yeast Schizosaccharomyces pombe, both cell size(6) and nutritional conditions(9) have been shown to affect cycle kinetics. The organism has been used extensively as a model eukaryotic system, largely because of the ease of measuring cell size and because division occurs by binary fission(11). More recently, its genetic tractability has led to the isolation of cell division cycle (cdc) mutants(12), and also of wee mutants altered in the control coordinating growth with the division cycle(13-15). The existence of such control mutants allows a more direct approach to the investigation of the molecular basis of division control, in contrast to the indirect methods used in other systems(4,16-18). wee mutants are so far unique to S. pombe. The most conspicuous property of wee mutants is their reduced cell size(13,14). Analysis of these mutants(15,19) and other evidence(9) has shown that control over cell division timing normally acts at entry to mitosis. As the function of a number of cdc genes is specifically required for mitosis(12), interactions between wee and cdc mutants which affect mitosis might be expected. I report here that the mitotic defect caused by a defective cdc25 allele is suppressed in wee mutants. Suppression by wee1 mutants is almost complete, while the wee2.1 mutation is a less effective suppressor. The significance of these findings for genetic models of the control of mitosis is considered.     

Chondroitin proteoglycans are involved in cell division of Caenorhabditis elegans

Glycosaminoglycans such as heparan sulphate and chondroitin sulphate are extracellular sugar chains involved in intercellular signalling. Disruptions of genes encoding enzymes that mediate glycosaminoglycan biosynthesis have severe consequences in Drosophila and mice. Mutations in the Drosophila gene sugarless, which encodes a UDP-glucose dehydrogenase, impairs developmental signalling through the Wnt family member Wingless, and signalling by the fibroblast growth factor and Hedgehog pathways. Heparan sulphate is involved in these pathways, but little is known about the involvement of chondroitin. Undersulphated and oversulphated chondroitin sulphate chains have been implicated in other biological processes, however, including adhesion of erythrocytes infected with malaria parasite to human placenta and regulation of neural development. To investigate chondroitin functions, we cloned a chondroitin synthase homologue of Caenorhabditis elegans and depleted expression of its product by RNA-mediated interference and deletion mutagenesis. Here we report that blocking chondroitin synthesis results in cytokinesis defects in early embryogenesis. Reversion of cytokinesis is often observed in chondroitin-depleted embryos, and cell division eventually stops, resulting in early embryonic death. Our findings show that chondroitin is required for embryonic cytokinesis and cell division.     

Structural insight into filament formation by mammalian septins

Septins are GTP-binding proteins that assemble into homo- and hetero-oligomers and filaments. Although they have key roles in various cellular processes, little is known concerning the structure of septin subunits or the organization and polarity of septin complexes. Here we present the structures of the human SEPT2 G domain and the heterotrimeric human SEPT2-SEPT6-SEPT7 complex. The structures reveal a universal bipolar polymer building block, composed of an extended G domain, which forms oligomers and filaments by conserved interactions between adjacent nucleotide-binding sites and/or the amino- and carboxy-terminal extensions. Unexpectedly, X-ray crystallography and electron microscopy showed that the predicted coiled coils are not involved in or required for complex and/or filament formation. The asymmetrical heterotrimers associate head-to-head to form a hexameric unit that is nonpolarized along the filament axis but is rotationally asymmetrical. The architecture of septin filaments differs fundamentally from that of other cytoskeletal structures.     

<Emphasis Type="Italic">ftsZ</Emphasis> gene and plastid division

As the important cellular organelles in plants, plas-tids comprise one of the primary features that distinguish plant cells from those of other eukaryotes. Seen from the origin, plastids derive from endosymbiotic photosynthetic bacteria. Subsequently, plastids have evolved to become essential components for plant cell function. Besides the important role of chloroplasts in photosynthesis, some water-soluble proteins that involved in biosynthesis of starch, fatty acids, amino acids, nucleic aci…     

The essential bacterial cell-division protein FtsZ is a GTPase.

Cytokinesis defines the last stage in the division cycle, in which cell constriction leads to the formation of daughter cells. The biochemical mechanisms responsible for this process are poorly understood. In bacteria, the ftsZ gene product, FtsZ, is required for cell division, playing a prominent role in cytokinesis. The cellular concentration of FtsZ regulates the frequency of division and genetic studies have indicated that it is the target of several endogenous division inhibitors. At the time of onset of septal invagination, the FtsZ protein is recruited from the cytoplasm to the division site, where it assembles into a ring that remains associated with the leading edge of the invaginating septum until septation is completed. Here we report that FtsZ specifically binds and hydrolyses GTP. The reaction can be dissociated into a GTP-dependent activation stage that is markedly affected by the concentration of FtsZ, and a hydrolysis stage in which GTP is hydrolysed to GDP. The results indicate that GTP binding and hydrolysis are important in enabling FtsZ to support bacterial cytokinesis, either by facilitating the assembly of the FtsZ ring and/or by catalysing an essential step in the cytokinetic process itself.     

An inducible DNA replication-cell division coupling mechanism in E. coli

Cell division is a tightly regulated periodic process. In steady-state cultures of Enterobacteriaceae, division takes place at a well defined cell mass and is strictly coordinated with DNA replication. In wild-type Escherichia coli the formation of cells lacking DNA is very rare, and interruptions of DNA replication arrest cell division. The molecular bases of this replication-division coupling have been elusive but several models have been proposed. It has been suggested, for example, that the termination of a round of DNA replication may trigger a key event required for cell division. A quite different model postulates the existence of a division inhibitor which prevents untimely division and whose synthesis is induced to high levels when DNA replication is perturbed. The work reported here establishes the existence of the latter type of replication-division coupling in E. coli, and shows that the sfiA gene product is an inducible component of this division inhibition mechanism which is synthesized at high levels after perturbations of DNA replication.