Nuclear targeting signal recognition: a key control point in nuclear transport?

Recent progress indicates that there are multiple pathways of nucleocytoplasmic transport which involve specific targeting sequences, such as nuclear localization sequences (NLSs), and cytosolic receptor molecules of the importin/karyopherin superfamily which recognise and dock the NLS-containing proteins at the nuclear pore. This first step of nuclear import/export is of central importance, with the affinity of the importin-targeting sequence interaction a critical parameter in determining transport efficiency. Different importins possess distinct NLS-binding specificities, which allows the system to be modulated through differential expression of the importins themselves, as well as through competition between different importins for the same protein, and between different proteins for the same importin. The targeting sequence-importin interaction can also be influenced directly by phosphorylation increasing the affinity of the interaction with importins or by targeting sequence masking through phosphorylation or specific protein binding. Targeting sequence recognition thus appears to represent a key control point in the regulation of nuclear transport. BioEssays 22:532-544, 2000.     

NIRF, a novel ubiquitin ligase, interacts with hepatitis B virus core protein and promotes its degradation

Hepatitis B virus (HBV) core protein (HBc) is a major component of viral nucleocapsid and a multifunctional protein involved in viral maturation and release. It is unstable and present in cells at low level because of K96 lysine residue, which is a ubiquitin acceptor site. Np95/ICBP90-like RING finger protein (NIRF) has auto-ubiquitination activity which is the hallmark of a ubiquitin ligase. In the present study, ubiquitin ligase, NIRF, binds to HBc and leads to the proteasome-mediated degradation of HBc in vivo. NIRF down-regulates HBc protein level, resulting in the decrease of the amount of HBV particles in supernatant of HepG2.2.15 cells. However knockdown of NIRF significantly increases endogenous HBc protein level, leading to HBV release. The results reveal that NIRF interacts with HBc and promotes the degradation of HBc in vivo. The pathway of NIRF-mediated ubiquitin–proteasome affects the release of HBV particles by controlling the amounts of HBc. It indicates that NIRF may participate in the maturation of HBV.     

昆虫保幼激素促进家蚕杆状病毒系统的基因表达

杆状病毒表达载体系统(Baculovirus Expression VecterSvstem,BEVS)的一个最大优点是外源基因的高效表达(Hy-perexpression).但是,不同的外源基因在BEVS系统中的表达水平相差很大,较低的如α-干扰素,表达量为1～5mg/L培养细胞;高的如β-半乳糖苷酶,表达量可达600mg/L培养细胞.外源基因在BEVS系统中表达量受到诸多因素的影响,如细胞的类型与质量,外源基因蛋白的性质,启动子序列的完整性,是否为融合蛋白等[1].如何使外源基因在BEVS系统中高效表达,是近年来该领域中研究最活跃的方向之一.已证实家蚕杆状病毒的表达量受宿主遗传型的影响,最低和最高的遗传型相差达7倍以上[2].林水中等发现家蚕饲料中添食适当浓度的硫酸铜可提高外源基因单位表达量10%左右[3].杆状病毒在复制循环中表现出两种类型:芽生病毒和包涵体病毒,其中芽生病毒引起宿主体内不同组织间的感染,包涵体病毒则引起宿主之间感染[1].杆状病毒基因组中蜕皮激素尿苷二磷酸葡萄糖基转移酶(egt)基因影响激素在宿主体内的平衡[4],egt基因通过糖基化作用使蜕皮激素失活,打破宿主体内的激素平衡,延长幼虫期,以利于病毒的增殖[5].家蚕血淋巴中保幼激素(Juvenile hormone,JH)的滴度同样决定着幼虫发育的进程[6],本文通过体表使用保幼激素,以研究保幼激素对家蚕核型多角体病毒和宿主之间的相互关系及对外源基因表达量的影响.     

新疆罗布麻生态类型及其纤维品质研究

新疆塔里木河及叶尔羌河流域是我国能够提供商品精干罗布麻的主要地区。由于野生罗布麻生长高矮不一,形态各异,与其纤维品质的相关性较大。通过40个株号的罗布麻植株形态和纤维长度等的的测定,分析各类型罗布麻的纤维长度和罗布麻植株各部分纤维长度情况。研究结果表明：罗布红麻高杆类型主茎纤维最长,罗布麻放牧类型纤维最短。罗布麻植株各部分纤维长度是主茎上的大于分枝,主茎中部的最长,基部和梢部最短。为野生罗布麻资源开发利用提科学依据。     

Secretion of firefly luciferase in E.coli

Summary A DNA segment carrying the full-length, intronless firefly luciferase gene was inserted into the high expression secretion vector, pIN-III -ompA. Upon induction of gene expression, luciferase activity was detected in extracts prepared from periplasmic fractions. The results indicated that the OmpA signal peptide was able to direct secretion of firefly luciferase across the cytoplasmic membrane. This has important implications for using this luciferase as a reporter in studying protein export and targeting.     

应用GeneXpert MTB/RIF对肺外结核的快速检测及评估

目的 评估GeneXpert MTB/RIF检测肺外结核分枝杆菌的准确性,并与传统方法进行比较。 方法 选取2016年6月至2017年6月在本院就诊的144例疑似肺外结核病患者,对所有标本分别进行金胺“O”荧光染色镜检、液体培养及药敏试验、固体培养及比例法体外药敏试验和Xpert法检测。 结果 收集的144例疑似肺外结核标本中,确诊108例,以胸水、淋巴结活检和脓液感染较多,另36例阴性患者中,10例为非结核分枝杆菌感染。Xpert试验的敏感性为28.73%,特异性为96.00%,其阳性预测值和阴性预测值均高于其他3种检测方法。在阳性检出率方面,Xpert试验高于涂片镜检(χ2=17.39,P2=8.64,P2=2.56,P>0.05)。固体培养、液体培养和Xpert试验3种方法对结核分枝杆菌利福平耐药率检测差异无统计学意义(P>0.05),耐药率分别为8.33%、9.68%和11.11%,且Xpert试验方法检测出2株耐多药结核分枝杆菌,平均耗时2.5 h。 结论 GeneXpert MTB/RIF可以作为一种筛选及快速检测工具应用于肺外结核的诊断,同时可作为检测MDR TB的一种指标。