大鼠神经元Arnt2亚细胞定位的预测与分析

目的:分析大鼠小脑颗粒神经元Arnt2的亚细胞定位情况。 方法:利用CBS生物信息资源，根据Arnt2氨基酸序列 (LOCUS：NP_036913) 进行真核生物亚细胞定位预测，并寻找Arnt2核输出信号(NES)；最后利用激光扫描共聚焦显微术(LSM) 确定Arnt2在正常大鼠小脑颗粒神经元中的亚细胞定位情况。 结果:预测Arnt2在真核生物细胞中主要为细胞核定位，并具有线粒体定位的可能性；预测结果还显示Arnt2氨基酸序列上存在着核输出信号，具体位置为氨基端第143位亮氨酸；LSM分析结果证实Arnt2定位于大鼠小脑颗粒神经元细胞核内。 结论:Arnt2定位于正常大鼠小脑颗粒神经元细胞核内；Arnt2具有线粒体定位的可能性，并存在核输出信号，提示在某些诱导因素作用下,Arnt2存在线粒体定向转位的趋势。     

神经母细胞瘤SK-N-SH细胞内DHRS4L2基因一种新选择性剪接亚型S4的克隆和亚细胞定位

目的 神经母细胞瘤SK-N-SH细胞系脱氢酶/还原酶(SDR家族)成员4类2[dehydrogenase/reductase(SDR family)member 4 like 2,DHRS4L2]基因的一种新的选择性剪接亚型克隆、生物信息学分析及其亚细胞定位.方法 以SK-N-SH细胞cDNA为模板,PCR扩增DHRS4基因簇Ea1转录本.将PCR产物A-T克隆至pGEMT-Easy质粒,对质粒进行DNA Sanger测序.将测序所得序列用NCBI ORF finder分析其编码区,用Motif Scan分析预测蛋白氨基酸序列.用Clustal Omega进行蛋白序列比对分析.将新亚型完整编码框cDNA以及删除偶核定位信号的编码框分别插入pEGFP-C1质粒,所得质粒和空质粒分别转染SK-N-SH细胞,在荧光显微镜下观察转染表达蛋白亚细胞定位.结果 用RT-PCR和Sanger测序方法发现,SK-N-SH表达DHRS4L2 Ea1转录本,未检测到其表达脱氢酶/还原酶(SDR家族)成员4类1[dehydrogenase/reductase(SDR family)member 4 like 1,DHRS4L1]的Ea2转录本.DHRS4L2 Ea1表达一个新的选择性剪接亚型DHRS4L2-S4(KU141377),由AY616183基础上在Ea1与E2外显子之间插入新外显子Ej形成,外显子Ej含有新亚型翻译起始密码子ATG.转录本KU141377预测蛋白羧基端具有偶核定位信号(bipartite nuclear localization signal,NLS),提示其可能定位于细胞核.绿色荧光蛋白融合蛋白实验显示,在SK-N-SH细胞该蛋白定位于细胞核.该蛋白还含有一个甘氨酸密集区(glycine-rich region)和阿片样生长因子受体重复(opioid growth factor receptor repeat)序列.结论 研究发现SK-N-SH细胞表达的一种DHRS4L2新选择性剪接亚型KU141377,其预测编码蛋白含有细胞偶核定位信号,融合荧光蛋白实验显示该新亚型定位于细胞核,这为后续研究DHRS4L2在神经母细胞瘤中的潜在功能奠定基础.     

不同分子亚型乳腺癌细胞系中RUNX3蛋白表达及定位研究

目的:检测人类Runt相关转录因子3(RUNX3)在不同分子亚型乳腺癌细胞系中的表达及其亚细胞定位情况,为进一步揭示RUNX3的失活机制和发现新的治疗靶点提供理论依据。方法:在5种乳腺癌细胞(MCF-7、T47D、SKBR-3、MDA-MB-231和BT-549)及正常乳腺上皮细胞(MCF-10A)中,通过Western blot和免疫荧光实验检测RUNX3的蛋白表达和亚细胞定位情况;采用来普霉素B(Leptomycin B)抑制RUNX3的出核,利用CCK-8法检测细胞活力的改变,EdU染色检测细胞增殖情况,Western blot和免疫荧光实验检测RUNX3的蛋白表达和亚细胞定位的改变。结果:与MCF-10A细胞相比,5种乳腺癌细胞系中RUNX3的核定位减少、胞浆定位增多。经Leptomycin B处理后,CCK-8实验结果显示5种乳腺癌细胞的活力明显减弱,EdU染色显示5种乳腺癌细胞增殖能力明显降低,Western blot和免疫荧光实验显示5种乳腺癌细胞胞浆中的RUNX3蛋白表达量明显降低、胞核中的RUNX3蛋白表达量明显增多(P0.05)。结论:不同分子亚型乳腺癌细胞中均存在RUNX3的胞浆转位失活现象,针对性地逆转RUNX3的出核过程可以明显降低肿瘤细胞的活力和增殖能力,可能成为乳腺癌潜在的治疗靶点。     

长链非编码RNA亚细胞定位和功能的研究进展

长链非编码RNA(lncRNA)的亚细胞定位和其功能息息相关，定位于细胞核时，lncRNA可以维持染色质结构，调控基因转录，参与mRNA的可变剪接；定位于细胞质时参与信号传导、转录后调控、翻译和翻译后修饰；定位于细胞器时协助完成细胞器的功能。lncRNA的亚细胞定位机制与其自身序列、结合蛋白等密切相关。此外通过构建核滞溜载体Snovector、添加胞质定位元件等强制改变lncRNA的亚细胞定位，以及利用APEX2等技术研究lncRNA亚细胞定位和其功能之间的关系，有利于lncRNA疗法的开发。     

非小细胞肺癌中P53表达的不同亚细胞定位及功能意义的研究

目的:探讨非小细胞肺癌(NSCLC)中不同亚细胞定位P53蛋白及其可能的功能意义。方法:以免疫组化及流式细胞分析术研究了43例NSCLC病人肿瘤组织P53表达定位与G₁/S检查点功能及DNA含量的关系。结果:发现P53蛋白不同的亚细胞定位与病人的病程密切相关,同时,在P53核表达定位的病人肿瘤组织细胞S期比例明显增多而G₀－G₁期比例明显较胞浆表达病人减少,G₂－M期比例及DNA指数在两组间无明显差异。结论:不同亚细胞定 位的P53蛋白具有不同的G₁/S检查点调节功能,胞浆P53蛋白仍有部分G₁/S检查点调控功能,因此出现较少的SPF及较多的G₀－G₁细胞,代表了恶性度较低的细胞亚群;而核表达阳性P53蛋白具有更差的G₁/S检查点调控功能,代表了恶性度较高的肿瘤亚群,这与肿瘤进展可能有关。     

强迫游泳大鼠脑内信号分子ERK1/2磷酸化水平的变化

通过观察强迫游泳时大鼠脑内不同核团内ERK1/2磷酸化水平变化,探讨与负性心理应激有关的脑内环路。将大鼠置于高60cm、水深约30cm的玻璃缸内,先预游15min,24h后进行5min的强迫游泳,观察大鼠游泳过程中的不动时间。游泳完毕后将大鼠灌流处死,对全脑组织进行磷酸化ERK1/2(pERK1/2)的免疫组织化学染色及其与酪氨酸羟化酶(TH)在部分核团内的免疫荧光双标细胞。强迫游泳后前额叶皮质、外侧隔区、下丘脑室旁核、海马CA13区、杏仁内侧亚核和皮质亚核、孤束核等脑区/核团中pERK1/2阳性细胞数显著增多;而杏仁中央亚核、下丘脑视上核内的磷酸化ERK1/2蛋白水平下降,阳性细胞数明显减少。免疫荧光双标结果表明,孤束核内部分pERK1/2阳性细胞呈TH免疫反应阳性。上述结果表明,以上脑区/核团内的神经元可能和负性心理应激的中枢调控有关,ERK1/2信号通路参与了其调控过程。此外,孤束核中的儿茶酚胺能神经元可能参与了心理应激的脑内活动。     

人胆酸转运蛋白基因的克隆、亚细胞定位及其在肾组织中的表达

目的：克隆人肾与小肠ASBT（顶端Na+/胆汁酸协同转运蛋白）基因并比较2者的序列差别，明确ASBT蛋白在肾小管上皮的亚细胞定位及在人肾组织中的表达情况。方法:从人肾和小肠组织中提取总RNA，然后用带有8肽FLAG标签的PCR引物通过RT-PCR技术扩增ASBT全长cDNA基因并测序，并将其插入真核表达载体中构建ASBT蛋白真核表达载体，然后将其转染到肾小管上皮细胞LLC-PK1中表达并用免疫荧光-激光共聚焦显微镜观察该蛋白的亚细胞定位情况。用免疫组化技术观察ASBT在人肾组织中的表达分布。结果:序列分析结果表明肾小管ASBT基因的序列与小肠ASBT序列完全一致。Western blotting表明ASBT基因在LLC-PK1细胞中得到了正确的表达。共聚焦显微镜分析显示正常ASBT蛋白主要定位于肾小管上皮细胞膜上，与生物信息学的预测结果一致。免疫组化染色表明ASBT蛋白主要表达于人近端肾小管上皮的刷状缘侧，在间质及远端小管没有表达。结论:人肾小管ASBT基因序列与小肠ASBT相同，ASBT蛋白主要表达于近端肾小管上皮细胞管腔侧细胞膜。     

pEGFP-SPAST真核表达载体的构建及遗传性痉挛性截瘫的发病机制研究

目的 构建野生型和突变型SPAST真核表达载体,研究SPAST基因突变所致遗传性痉挛性截瘫的发病机制.方法 建立野生型pEGFP-SPAST基因表达载体,采用overlap PCR方法构建突变型pEGFP-SPAST真核表达载体.细胞转染野生型和突变型pEGFP SPAST真核表达载体,观察野生型和突变型spastin蛋白在COS-7细胞中的表达,采用免疫荧光染色技术观察spastin蛋白与微管、线粒体的定位关系.结果 野生型和突变型spastin蛋白均在细胞质中表达.免疫荧光检测发现野生型和突变型spastin蛋白均不与微管共定位,也均不与线粒体共定位.结论 成功构建了野生型和突变型pEGFP-SPAST真核表达载体.突变型spastin蛋白不改变其细胞质定位.功能研究提示spastin蛋白可能不直接调控微管功能和线粒体功能.     

BS69 在结直肠癌组织中的表达以及病理相关性研究

目的:探讨BS69在结直肠癌组织及细胞系中蛋白和mRNA的表达水平,分析BS69与患者病理特征的相关性。方法:选择2016年8月至2017年10月间手术切除的60例结直肠癌组织和25例癌旁正常组织,采用免疫组化和RTq PCR法检测组织中BS69蛋白和mRNA的表达情况。采用蛋白印迹(Western blot)法检测BS69在三种结直肠癌细胞系和正常结直肠上皮细胞中的蛋白表达。结果:BS69免疫组化染色主要定位于细胞核,少量位于细胞浆。其在结直肠癌和正常结直肠组织中的阳性率分别为65%和87%,差异具有统计学意义(P0. 05); BS69在结直肠癌组织中的表达水平与Dukes分期、肿瘤组织分级、淋巴结转移及远处转移有相关性(P0. 05); Western blot检测BS69在3种结直肠癌细胞系与正常结直肠上皮细胞中蛋白表达,各细胞系中结果有明显差异;结直肠癌组织中BS69 mRNA的表达明显低于正常组织,差异有统计学意义(P0. 05)。结论:BS69是重要的转录抑制因子,可能参与了结直肠癌的发生、发展过程,有望成为特异性较高的肿瘤标志物。     

Characterization of the nuclear localization signal in the DNA helicase responsible for Bloom syndrome

Bloom syndrome (BS) is a rare genetic disorder characterized by small body size, photosensitivity, immunodeficiency and a high predisposition to various types of cancer. BLM was identified as the causative gene for BS. The BLM protein is homologous to DNA helicase and has two basic amino acid clusters in its C-terminal region. Previously, we reported that the distal arm of these basic amino acids clusters in the BLM protein functioned as the nuclear localization signal (NLS) of the protein. In this study, we generated plasmid constructs for expression of enhanced green fluorescent protein (EGFP) fused with various BLM protein variants having a mutation with deletions or substitutions in the basic amino acid and analyzed the subcellular localization of the expressed proteins. The EGFP-fused protein containing the basic amino acid cluster region proximal to the C-terminus of BLM helicase was localized exclusively in the nucleus. However, the EGFP-BLM proteins that lacked either Arg1344 or Lys1346 distributed in both the cytoplasm and the nucleus equally. Deletion of Arg1347 also resulted in localization in both the nucleus and cytoplasm, and substitution of Arg1344, Lys1346, Arg1347 or Arg1348 with non-basic amino acids reduced the nuclear localization of BLM protein. Mouse BLM protein which also migrate to the nucleus has two basic amino acid clusters in the C-terminus and the basic amino acids (Lys1346-Pro1347-Lys1348-Arg1349-Arg1350) proximal to the C-terminus are conserved between mouse and human. These findings suggest that the Arg1344-Ser1345-Lys1346-Arg1347 sequence at the C-terminus of the human BLM protein is essential for nuclear localization of this protein.     

A CRM1-dependent nuclear export pathway is involved in the regulation of MutLα subcellular localization

MutLα plays an essential role in DNA mismatch repair (MMR) and is additionally involved in other cellular mechanisms such as the regulation of cell cycle checkpoints and apoptosis. Therefore, not only germline MMR gene defects but also the subcellular localization of MutLα might be of importance for the development of Lynch syndrome. Recently, we showed that MutLα contains functional nuclear import sequences and is most frequently localized in the nucleus. Here, we demonstrate that MutLα can move bidirectionally towards the nuclear membrane. Using MutLα transfected HEK293T cells we observed a significant shift of MLH1 and PMS2 from the nucleus to the cytoplasm after irradiation or cisplatin treatment. We analyzed both proteins for potential nuclear export sequences (NES) and identified one functional Rev‐type NES ( ⁵⁷⁸ LFDLAMLAL) in the C‐terminal part of MLH1 that facilitates export via the CRM1/exportin pathway. Moreover, an MLH1‐NES mutation detected in a patient with Lynch syndrome showed normal MMR activity but led to significantly impaired cytoplasmic transport after actinomycin D treatment. These results indicate that MutLα is able to shuttle from the nucleus to the cytoplasm, probably signaling DNA damages to downstream pathways. In conclusion, not only a defective MMR but also impaired nucleo‐cytoplasmic shuttling might result in the onset of Lynch syndrome. © 2010 Wiley‐Liss, Inc.     

A novel virus-encoded nucleocytoplasmic shuttling protein: the UL3 protein of herpes simplex virus type 1

Herpes simplex virus type 1 (HSV-1) UL3 protein is a nuclear protein. In this study, the molecular mechanism of the subcellular localization of UL3 was characterized by fluorescence microscopy in living cells. A nuclear localization signal (NLS) and a nuclear export signal (NES) were also identified. UL3 was demonstrated to target to the cytoplasm through the NES via chromosomal region maintenance 1 (CRM-1) dependent pathway, and to the nucleus through RanGTP-dependent mechanism. Heterokaryon assays confirmed that UL3 was capable of shuttling between the nucleus and the cytoplasm. These results demonstrate that the UL3 protein is a novel HSV-1 encoded nucleocytoplasmic shuttling protein.     

Nuclear export of Far1p in response to pheromones requires the export receptor Msn5p/Ste21p

Far1p is a bifunctional protein that is required to arrest the cell cycle and to establish cell polarity during yeast mating. Far1p is localized predominantly in the nucleus but accumulates in the cytoplasm in cells exposed to pheromones. Here we show that Far1p functions in both subcellular compartments: nuclear Far1p is required to arrest the cell cycle, whereas cytoplasmic Far1p is involved in the establishment of cell polarity. The subcellular localization of Far1p is regulated by two mechanisms: (1) Far1p contains a functional bipartite nuclear localization signal (NLS), and (2) Far1p is exported from the nucleus by Msn5p/Ste21p, a member of the exportin family. Cells deleted for Msn5p/Ste21p failed to export Far1p in response to pheromones, whereas overexpression of Msn5p/Ste21p was sufficient to accumulate Far1p in the cytoplasm in the absence of pheromones. Msn5p/Ste21p was localized in the nucleus and interacted with Far1p in a manner dependent on GTP-bound Gsp1p. Two-hybrid analysis identified a small fragment within Far1p that is necessary and sufficient for binding to Msn5p/Ste21p, and is also required to export Far1p in vivo. Finally, similar to Deltamsn5/ste21 strains, cells expressing a mutant Far1p, which can no longer be exported, exhibit a mating defect, but are able to arrest their cell cycle in response to pheromones. Taken together, our results suggest that nuclear export of Far1p by Msn5p/Ste21p coordinates the two separable functions of Far1p during mating.     

Carboxyl-terminal basic amino acids in the X domain are essential for the nuclear import of phospholipase C delta1

BACKGROUND: Although phospholipase C (PLC)delta1 containing a functional nuclear export signal (NES) is normally localized at the plasma membrane and in the cytoplasm, it shuttles between the nucleus and the cytoplasm. Since nucleocytoplasmic shuttling of a molecule is generally regulated by a balance between its NES and the nuclear localization signal (NLS), we examined whether PLCdelta1 contains an NLS sequence. RESULTS: A region corresponding to the C terminus of the X domain and the XY-linker, which contains clusters of basic amino acid residues, was essential for the nuclear import of PLCdelta1 in Madin-Darby canine kidney cells. A series of point mutations on lysine residues in this region revealed that K432 and K434 in combination were important for the nuclear import. A short synthetic peptide corresponding to residues 429-442, however, was not able to function as an NLS sequence when they were injected into the cytoplasm in a carrier-conjugated form. Neither a longer peptide equivalent to PLCdelta1 412-498 fused to a protein tag consisting of glutathione S-transferase and green fluorescent protein was imported to the nucleus after microinjection into the cytoplasm. CONCLUSION: The nuclear import of PLCdelta1 requires the C-terminus of the X domain, particularly the amino acid residues K432 and K434, and the XY-linker. The region alone, however, cannot serve as a functional NLS. The machinery for nuclear transport may require additional structural component(s) of the enzyme.     

Intracellular traffic of the progesterone receptor]

The nuclear localization of the progesterone receptor is mediated by two signal sequences: one is constitutive and lies in the hinge region (between the DNA and steroid binding domains), the other is hormone-dependent and is localized in the second zinc finger of the DNA binding domain. The use of various inhibitors of energy synthesis in cells expressing permanently or transiently the wild-type receptor or a receptor mutated within the nuclear localization signals, demonstrated that the nuclear residency of the receptor reflects a dynamic situation: the receptor diffusing into the cytoplasm and being constantly and actively transported back into the nucleus. The existence of this nucleo-cytoplasmic shuttle mechanism was confirmed by receptor transfer from one nucleus to the other in heterokaryons. Preliminary evidence was obtained, using oestrogen receptor, that this phenomenon may be of general significance for steroid receptors.     

Characterization of signal sequences determining the nuclear export of Newcastle disease virus matrix protein

The Newcastle disease virus (NDV) matrix (M) protein has been demonstrated to be a nuclear-cytoplasmic trafficking protein. Previous studies have shown that the M protein localizes in the nucleus through a bipartite nuclear localization signal. Here, we report that the ability of the M protein to shuttle to the cytoplasm is mediated by three nuclear export signal sequences (NESs). Using leptomycin B (LMB), a specific inhibitor of CRM1, we found that the nuclear export of the three NESs was LMB insensitive and thus was CRM1 independent. In addition, inactivation of these NESs led to nuclear accumulation of the M protein. Our results highlight the significance of these NESs to the nuclear export of the NDV M protein.