结核分枝杆菌esat6-mpt64融合基因真核表达载体的构建

目的:构建结核分枝杆菌分泌蛋白基因esat6-mpt64的真核表达载体。方法:用PCR法从结核分枝杆菌H37Rv株基因组中分别扩增esat6、mpt64基因,插入pGEM-T-easy载体,序列测定正确后,将其亚克隆到真核表达载体pcDNA3.1( );重组质粒经酶切鉴定正确后,用LipofectAMINE2000转染COS-7细胞;用RT-PCR检测mRNA的表达,用间接免疫荧光技术检测目的蛋白的表达。结果:RT-PCR表明esat6-mpt64融合基因可在COS-7细胞中转录;用间接免疫荧光检测,有表达蛋白的细胞着染。结论:构建了真核表达载体pcDNA-esat6-mpt64,并在真核COS-7细胞中表达。     

结核分枝杆菌Rv3586结构域基因真核表达载体的构建及鉴定

目的:构建结核分枝杆菌(Mycobacterium tuberculosis,Mtb)环二腺苷酸(cyclic diadenosine monophosphate,c-di-AMP)合成酶Rv3586结构域基因的真核表达载体,并在COS-7细胞中表达。方法:以Mtb基因组为模板PCR扩增Rv3586三个结构域基因,分别克隆入pEGFP-N3真核表达质粒,用菌落PCR、质粒酶切和测序方法对插入序列进行鉴定。通过脂质体将重组质粒转染COS-7细胞,间接免疫荧光法检测目的基因在COS-7细胞内的表达。结果:PCR成功扩增出Rv3586三个结构域基因,菌落PCR、质粒酶切和质粒测序鉴定结果表明成功插入目的片段,包含Rv3586的三个结构域基因的真核表达载体构建成功。间接免疫荧光法结果显示,Rv3586三个结构域蛋白在COS-7细胞中表达成功。结论:成功构建Rv3586三个结构域基因的真核表达载体,并在COS-7细胞中表达成功,为后续Mtb Rv3586结构域的功能和应用研究奠定了基础。     

eIF4A在帽依赖和IRES介导的翻译起始中的作用

生物体内翻译起始机制分为两类：帽依赖性翻译起始和内部核糖体进入位点(internal ribosome entry sites, IRES)介导的翻译起始。真核生物的翻译起始为经典的帽依赖性翻译起始模型,而大多数正链RNA病毒选择依赖于IRES的翻译机制。真核翻译起始因子4A (eukaryotic initiation factor 4A, eIF4A)是DEAD-box RNA解旋酶家族的成员,具有依赖于RNA的ATP酶活性和RNA解旋酶活性,而e IF4A具体的解旋机制至今仍不清晰。同时,eIF4A与其他翻译因子有着复杂而紧密的联系,在帽依赖性与IRES介导的翻译起始过程中扮演着至关重要的角色。本文主要对eIF4A的功能、结构以及eIF4A在帽依赖性与IRES介导的翻译起始过程中的机制作一综述。     

MIC3-EGFP融合蛋白真核表达质粒的构建及其在COS-7细胞中的表达

目的:构建以绿色荧光蛋白(greenfluoreseeneeprotein,GFP)为报告基因的重组表达质粒pEGFP-C2-MIC3并检测MIC3-EGFP融合蛋白其在COS-7细胞中的表达及定位.方法:通过基因重组的方法构建pEGFP-C2-MIC3重组真核表达质粒,并通过酶切和基因测序鉴定.脂质体法转染体外培养的COS-7细胞,转染后24h在活细胞状态下用倒置荧光显微镜直接观察MIC3-EGFP融合蛋白在COS-7细胞中的分布.结果:PCR检测,酶切鉴定及测序证实目的基因MIC3正确连接到pEGFP-C2的多克隆位点.pEGFP-C2-MIC3重组体转染COS-7后,在细胞质表达.结论:成功地构建了pEGFP-C2-MIC3融合蛋白真核表达质粒,在COS-7细胞中获得表达.     

核酸疫苗双表达载体的构建及表达

将微小病毒内部核糖体进入位点(IRES)基因克隆到质粒pVAXI载体多克隆位点,构建出核酸疫苗双表达载体pVI。将绿色荧光蛋白(EGFP)基因和新霉素磷酸转移酶(neor)基因作为报告基因,连接到pVI载体IRES基因的前后两处多克隆位点,构建出表达载体pEIN。通过脂质体介导的方法将该载体转染COS-7细胞,筛选到同时表达绿色荧光蛋白和新霉素磷酸转移酶的表达株,表明成功地构建了核酸疫苗双表达载体,为构建多价核酸疫苗及带有分子佐剂的核酸疫苗打下了基础。     

一种新的双元表达质粒pCMV-Myc-IRES-EGFP的构建及其表达

为了研究基因的特征、理化特性及其功能机制,通常需要构建多个真核表达载体,涉及到多次的引物设计、酶切、连接和鉴定等繁琐的亚克隆过程。构建携带易于多种实验研究的多用或通用载体是基因工程载体的发展方向。为此,利用pIRES载体为骨架质粒,在A和B多克隆位点上分别插入c-Myc标签蛋白序列和增强型绿色荧光蛋白(EGFP)序列,从而构建了一个包含c-Myc标签蛋白序列并携带有核糖体结合位点(IRES)介导的增强型绿色荧光蛋白的真核表达载体pCMV-Myc-IRES-EGFP。通过荧光检测和免疫印迹实验证实该载体能在哺乳细胞中表达。该载体可用于监测细胞的转染效率、分选稳定表达的阳性细胞群体、体外转录和翻译、检测或纯化目的蛋白以及捕获相关作用蛋白等多种实验研究,为基因功能研究提供了便利。     

基因枪介导真核表达质粒转染体外培养的COS-7细胞系的实验研究

目的：建立基因枪子弹制备及转染体外培养COS-7细胞系的方法。方法：以亚精氨、氯化钙沉淀法制备子弹（DNA＋金颗粒）,利用原子力显微镜观察子弹制备情况;采用基因枪方法分别将真核表达质粒pVax-Dsred-IRES-EGFP转染对照组和实验组COS-7细胞,转染后24h,利用激光扫描共聚焦显微镜观察细胞中红、绿荧光蛋白的表达。结果：制备了基因枪子弹,DNA紧密包裹在金颗粒周围;基因枪介导的pVax-Dsred-IRES-EGFP被转染入体外培养的COS-7细胞,转染后24h可检测到红、绿荧光,而对照组则没有荧光蛋白的表达。结论：国产新芝SJ-500型基因枪能够有效介导外源基因转移,基因枪转染的COS-7细胞能够有效表达报告基因。     

转录激活因子1(ATF1)内部核糖体进入位点的鉴定及活性分析

蛋白质翻译起始通常有两种机制,一是依赖帽结构的翻译,另一种是依赖5′非翻译区的内部核糖体进入位点(IRES).在后一种方式中,在某些IRES反式作用因子,如La蛋白、多聚嘧啶串结合蛋白1等的参与下,直接招募核糖体小亚基到mRNA的翻译起始位点,启始翻译.研究发现,参与细胞生长、分化、细胞周期进程、凋亡和压力调控的相关蛋白中通常含有IRES元件.基于功能,我们提出假说：转录激活因子1(ATF1)的5′-UTR可能具有IRES活性.为验证假说,首先构建了含全长ATF1 5′-UTR的双荧光素酶报告质粒|质粒转染结合报告酶活性分析显示,ATF1 5′-UTR在Bel7402、HCT-8和HEK293细胞中表现出不同的IRES活性|而此IRES活性与5′-UTR中的隐藏启动子无关.同时还发现,ATF1 5′-UTR在NIH3T3细胞中却没有IRES活性.与此结果相一致,Western印迹检测ATF1在这几种细胞系中的表达.结果显示,Bel7402、HCT 8和HEK293中ATF1蛋白质表达水平较高,而在NIH3T3中却极低. ATF1 5′-UTR的系列5′-删除突变及报告酶分析证明,ATF1 5′-UTR的完整性对其IRES活性大小发挥重要作用|其中5′端的204 bp序列对其IRES活性贡献较大. RNA-蛋白免疫共沉淀实验揭示,ATF1 5′-UTR可与La和PTBP1蛋白结合|抑制La和PTBP1蛋白质的表达,并可减低HEK293细胞中ATF1蛋白质表达水平.这些结果提示,La和PTBP1蛋白（两种ITAFs）为ATF1 5′-UTR发挥IRES活性所必需.总之,上述结果证明,ATF1 5′-UTR具有IRES活性,其活性发挥依赖与La和PTBP1蛋白的结合.上述发现为进一步研究La和PTBP1表达及亚细胞定位对ATF1 IRES调控机制的影响奠定了基础.     

T7 RNA聚合酶表达系统的真核化及其偶联表达系统的建立

为了使T7RNA聚合酶(T7RNAP)表达系统真核化,首先,利用两种方法建立能够表达T7RNAP的真核细胞:(1)共转染表达T7RNAP的真核表达重组质粒于靶细胞;(2)利用稳定表达T7RNAP的BHK-21细胞系。然后,将FMDV内部核糖体进入位点(IRES)序列和增强型绿色荧光蛋白(EGFP)基因定向克隆进原核载体pET-40a-c( )的T7启动子下游,得到的重组质粒pIERS-EGFP-E。用该质粒分别转染上述两种细胞,在紫外显微镜下都能够观察到绿色荧光,表明真核化的T7RNAP偶联表达系统建立。并利用流式细胞仪对偶联表达水平进行了分析。这为利用该系统真核高效表达外源蛋白奠定了坚实的基础。用实验证明了FMDV5′端含有IERS具有介导非帽依赖性的翻译的功能,为以IERS为基础的双顺反子表达系统的建立及深入研究IERS与相关蛋白的功能奠定了基础。T7RNAP偶联表达体系是一种良好的外源基因表达体系。     

人TIMP-1 cDNA克隆、真核表达载体构建及在COS-7细胞中的表达

根据 Gen Bank中 TIMP- 1基因的碱基序列 ,用 RT- PCR方法从人的正常肾组织中克隆出包含信号肽在内的 TIMP- 1全长 c DNA序列 .采用 T- A克隆的方法将之插入 p CRR2 .1中间载体 ,DNA测序证实该片段序列与文献报告的完全一致 .利用亚克隆的方法将 TIMP- 1 c DNA片段克隆到 pc DNA3载体上 ,构建出 pc DNA3/ TIMP- 1的真核表达载体 ,通过脂质体 DOTAP转染至 COS-7细胞 ,Northern印迹及原位杂交证实在 COS- 7细胞上获得人 TIMP- 1的高效表达 ,细胞增殖实验表明 TIMP- 1的高产表达可促进 COS- 7细胞的增殖 ,证实了所转染人 TIMP- 1的生物活性     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

Comparative morphology of the carpel in the Liliaceae: Hewardieae, Petrosavieae, and Tricyrteae

The young pistils in the melanthioid tribes, Hewardieae, Petrosavieae and Tricyrteae, are uniformly tricarpellate and syncarpous. They lack raphide idioblasts. All are multiovulate, with bitegmic ovules. The Petrosavieae are marked by the presence of septal glands and incomplete syncarpy. Tepals and stamens adhere to the ovary in the Hewardieae and the Petrosavieae but not in the Tricyrteae. Two vascular bundles occur in the stamens of the Hewartlieae and Tricyrtis latifolia. Ventral bundles in the upper part of the ovary of the Hewardieae are continuous with compound septal bundles and placental bundles in the lower part. Putative ventral bundles occur in the alternate position in the Tricyrteae and putative placental bundles in the opposite. position in the Petrosavieae. The dichtomously branched stigma in each carpel of the Tricyrteae is supplied by a bifurcated dorsal bundle.     

Enterovirus 71 3C proteolytically processes the histone H3 N-terminal tail during infection

Highlights
1. The N-terminal tail of histone H3 is specifically cleaved during EV71 infection.
2. Viral protease 3C is identified as a protease responsible for proteolytically processing the N-terminal H3 tail.
3. Our finding reveals a new epigenetic regulatory mechanism for Enterovirus 71 in virus-host interactions.     

Detection of EBV and HHV6 in the Brain Tissue of Patients with Rasmussen’s Encephalitis

Rasmussen’s encephalitis (RE) is a rare pediatric neurological disorder, and the exact etiology is not clear. Viral infection may be involved in the pathogenesis of RE, but conflicting results have reported. In this study, we evaluated the expression of both Epstein-Barr virus (EBV) and human herpes virus (HHV) 6 antigens in brain sections from 30 patients with RE and 16 control individuals by immunohistochemistry. In the RE group, EBV and HHV6 antigens were detected in 56.7% (17/30) and 50% (15/30) of individuals, respectively. In contrast, no detectable EBV and HHV6 antigen expression was found in brain tissues of the control group. The co-expression of EBV and HHV6 was detected in 20.0% (6/30) of individuals. In particular, a 4-year-old boy had a typical clinical course, including a medical history of viral encephalitis, intractable epilepsy, and hemispheric atrophy. The co-expression of EBV and HHV6 was detected in neurons and astrocytes in the brain tissue, accompanied by a high frequency of CD8⁺ T cells. Our results suggest that EBV and HHV6 infection and the activation of CD8⁺ T cells are involved in the pathogenesis of RE.     

Perinatal Vertical Transmission of Chikungunya Virus in Ruili,a Town on the Border between China and Myanmar

正Dear Editor,Chikungunya virus (CHIKV), an arbovirus in the family of Togaviridae, genus Alphavirus, is transmitted by the A.aegyptii or A. albopictus mosquito, and causes disease in humans characterized by fever, rash, and arthralgia (Silva and Dermody 2017; Suhrbier 2019). It was first reported in 1953 in Tanzania, and caused only a few outbreaks and sporadic cases in Africa and Asia in last century. However, in the epidemic in 2004, CHIKV acquired mutations that conferred enhanced transmission by the A. albopictus mosquito(Schuffenecker et al. 2006). Since then, it has successively caused outbreaks in Africa, the Indian Ocean, South East Asia, the South America, and Europe (Zeller et al. 2016).     

Development of a Novel Reverse Transcription Loop-Mediated Isothermal Amplification Method for Rapid Detection of SARS-CoV-2

In conclusion, the novel visual RT-LAMP assay is a simple, rapid, and sensitive approach for detection of SARS-CoV-2, and it is ready for application in primary care and community hospitals or health care centers, and even patients' own houses in response to the current SARS-CoV-2 epidemic because the assay does not require sophisticated equipment and skilled personnel. Furthermore, it is also ready to be used in fields for screening samples from wild animals and environments to facilitate the identification of potential intermediate hosts that mediate the cross-species transmission of SARS-CoV-2 from bats to humans.