Presence of a long nuclear-localization signal sequence in homeodomain transcription factor Nkx 1.2

Homeodomains,a 60-amino acid sequence encoded by 180 nucleotides,are highly conserved DNA-binding motifs that are present in a variety of transcription factors in species ranging from yeast to humans.The NKX proteins belong to the homeodomain(HD)-containing transcription factor family.They play vital roles in the regulation of morphogenesis.NKX1-2 is one member of the NKX subfamily.At present,information about its nuclear localization signal(NLS)sequence is limited.We studied the NLS sequence of zebrafish Nkx1.2 by introducing sequence changes such as deletion,mutation,and truncation,and identified an NLS motif(QNRRTKWKKQ)that is localized at the C-terminus of the homeodomain.Moreover,the deletion of two amino acid residues(RR)in this NLS motif prevents Nkx1.2 from entering the nucleus,indicating that the two amino acids are essential for Nkx1.2 nuclear localization.However,the NLS motif alone is unable to target cytoplasmic protein glutathione S-transferase(GST)to the nucleus.An intact homeodomain is necessary for mediating the complete nuclear transport of cytoplasmic protein.Unlike most nuclear import proteins with short NLS sequences,a long NLS is present in zebrafish Nkx1.2.We also demonstrated that the sequences of homeodomain of NKX1.2 are well conserved among different species.This study is informative to verify the function of the NKX1.2 protein.

Developing high-efficiency base editors by combining optimized synergistic core components with new types of nuclear localization signal peptide

The clustered regularly interspaced short palindromic repeats(CRISPR)–CRISPR-associated protein(Cas) system has been widely used for genome editing. In this system, the cytosine base editor(CBE) and adenine base editor(ABE) allow generating precise and irreversible base mutations in a programmable manner and have been used in many different types of cells and organisms. However, their applications are limited by low editing efficiency at certain genomic target sites or at specific target cytosine(C) or adenine(A) residues. Using a strategy of combining optimized synergistic core components, we developed a new multiplex super-assembled ABE(sABE) in rice that showed higher base-editing efficiency than previously developed ABEs. We also designed a new type of nuclear localization signal(NLS) comprising a FLAG epitope tag with four copies of a codon-optimized NLS(F4NLS^(r2)) to generate another ABE named F4NLS-sABE. This new NLS increased editing efficiency or edited additional A at several target sites. A new multiplex super-assembled CBE(sCBE) and F4NLS^(r2) involved F4NLS-sCBE were also created using the same strategy. F4NLS-sCBE was proven to be much more efficient than sCBE in rice. These optimized base editors will serve as powerful genome-editing tools for basic research or molecular breeding in rice and will provide a reference for the development of superior editing tools for other plants or animals.

Identification and characterization of a novel bipartite nuclear localization signal in the hepatitis B virus polymerase

AIM: To characterize the nuclear import of hepatitis B virus (HBV) polymerase (P) and its relevance for the viral life cycle.METHODS: Sequence analysis was performed to predict functional motives within P. Phosphorylation of P was analyzed by in vitro phosphorylation. Phosphorylation site and nuclear localization signal (NLS) were destroyed by site directed mutagenesis. Functionality of the identified NLS was analyzed by confocal fluorescence microscopy and characterizing the karyopherin binding. Relevance of the structural motives for viral life cycle was studied by infection of primary Tupaia hepatocytes with HBV.RESULTS: We identified by sequence alignment and functional experiments a conserved bipartite NLS containing a casein kinase II (CKII) phosphorylation site located within the terminal protein domain (TP) of the HBV polymerase. Inhibition of CKII impairs the functionality of this NLS and thereby prevents the nuclear import of the polymerase. Binding of the import factor karyopherin-α2 to the polymerase depends on its CKII-mediated phosphorylation of the bipartite NLS. In HBV-infected primary Tupaia hepatocytes CKII inhibition in the early phase (post entry phase) of the infection process prevents the establishment of the infection.CONCLUSION: Based on these data it is suggested that during HBV infection the final import of the genome complex into the nucleus is mediated by a novel bipartite NLS localized in the TP domain of HBV polymerase.

Identification and Characterization of Nuclear Localization Signals within the Nucleocapsid Protein VP15 of White Spot Syndrome Virus

The nucleocapsid protein VP15 of white spot syndrome virus (WSSV) is a basic DNA-binding protein. Three canonical bipartite nuclear localization signals (NLSs), called NLS1 (aa 11-27), NLS2 (aa 33-49) and NLS3 (44-60), have been detected in this protein, using the ScanProsite computer program. To determine the nuclear localization sequence of VP15, the full-length open reading frame, or the sequence of one of the three NLSs, was fused to the green fluorescent protein (GFP) gene, and transiently expressed in insect Sf9 cells. Transfection with full-length VP15 resulted in GFP fluorescence being distributed exclusively in the nucleus. NLS1 alone could also direct GFP to the nucleus, but less efficiently. Neither of the other two NLSs (NLS2 and 3) was functional when expressed alone, but exhibited similar activity to NLS1 when they were expressed as a fusion peptide. Furthermore, a mutated VP15, in which the two basic amino acids (11RR12) of NLS1 were changed to two alanines (11AA12), caused GFP to be localized only in the cytoplasm of Sf9 cells. These results demonstrated that VP15, as a nuclear localization protein, needs cooperation between its three NLSs, and that the two residues (11RR12) of NLS1 play a key role in transporting the protein to the nucleus.

A unique sequence in the N-terminal regulatory region controls the nuclear localization of KLF8 by cooperating with the C-terminal zinc-fingers

Kruppel-like factor 8 （KLF8） transcription factor plays a critical role in cell cycle progression, oncogenic transformation, epithelial to mesenchymal transition and invasion. However, its nuclear localization signal（s） （NLS） has not been identified. KLF8 shares with other KLFs monopartite NLSs （mNLS） and C2H2 zinc fingers （ZFs）, both of which have been shown to be the NLSs for some other KLFs. In this report, using PCR-directed mutagenesis and immunofluorescent microscopy, we show that disruption of the mNLSs, deletion of any single ZF, or mutation of the Zn^2＋-binding or DNA-contacting motifs did not affect the nuclear localization of KLF8. Deletion of 〉1.5 ZFs from Cterminus, however, caused cytoplasmic accumulation of KLF8. Surprisingly, deletion of amino acid （aa） 151-200 region almost eliminated KLF8 from the nucleus. S165A, K171E or K171R mutation, or treatment with PKC inhibitor led to partial cytoplasmic accumulation. Co-immunoprecipitation demonstrated that KLF8 interacted with importin-β and this interaction required the ZF motif. Deletion of aa 1-150 or 201-261 region alone did not alter the nuclear localization. BrdU incorporation and cyclin D1 promoter luciferase assays showed that the KLF8 mutants defective in nuclear localization could not promote DNA synthesis or cyclin D1 promoter activation as the wild-type KLF8 did. Taken together, these results suggest that KLF8 has two NLSs, one surrounding S165 and K171 and the other being two tandem ZFs, which are critical for the regulation of KLF8 nuclear localization and its cellular functions.

Computer-Assisted analysis of subcellular localization signals and post-translational modifications of human prion proteins

In the present work, computational analyses were applied to study the subcellular localiza-tion and posttranslational modifications of hu-man prion proteins (PrPs). The tentative location of prion protein was determined to be in the nu-cleolus inside the nucleus by the following bio-informatics tools: Hum-PLoc, Euk-PLoc and Nuc-PLoc. Based on our results signal peptides with average of 22 base pairs in N-terminal were identified in human PrPs. This theoretical study demonstrates that PrP is post-translationally modified by: 1) attachment of two N-linked complex carbohydrate moieties (N181 and N197), 2) attachmet of glycosylphosphatidylinositol (GPI) at serine 230 and 3) formation of two di-sulfide bonds between “6–22” and “179–214” cysteines. Furthermore, ten protein kinase phosphorylation sites were predicted in human PrP. The above-noted phosphorylation was car-ried out by PKC and CK2. By using bioinfor-matics tools, we have shown that computation-ally human PrPs locate particularly into the nu-cleolus.

A peptide of 17 aminoacids from the N-terminal region of maize plastidial transglutaminase is essential for chloroplast targeting

Transglutaminases (TGases, EC 2.3.2.13) catalyse posttranslational modification of proteins by establishing ε-(γ-glutamyl) links and covalent conjugation of polyamines. In plants, the functionality of these enzymes is scarcely known. The maize transglutaminase gene (tgz), the only cloned plant TGase, produces major alterations in thylakoid membrane architecture when the transglutaminase (chlTGZ) protein was over-expressed in tobacco chloroplasts, significantly increasing the number of grana stacked layers. Here we demonstrate that nuclear transformation of rice plants starting from a tgz gene truncated in 17 N-terminal aas (tgzt) non altered chloroplast thylakoid structures. F3 transformed plants were analysed for TGase activity, chlTGZ presence and tgzt transcription levels. Transformed plants exhibited double the in vitro TGase activity of the non-transformed plants. Immunoblot and quantitative RT-PCR analysis results of tgzt-rice plants grown under different illumination periods revealed that chlTGZ maintains its differential expression depending on the light regime. Nevertheless, the maize protein was localised by confocal microscopy in the cell wall of transformed rice cells. TEM analyses of the transformed cells showed normal, non-altered chloroplast thylakoid structures with the maize protein preferentially located in the cell walls. The results confirmed that the tgz eliminated sequence is essential for chloroplast targeting, being its absence sufficient to the lack of protein expression in its original plastidal compartment. Interestingly, the immunolocalization of a putative endogenous rice TGase protein is also showed. These data give further information on plant TGase functionality and its relationship to photosynthetic membranes.

Molecular Determinants Responsible for the Subcellular Localization of HSV-1 UL4 Protein

The function of the herpes simplex virus type 1 （HSV-1） UL4 protein is still elusive. Our objective is to investigate the subcellular transport mechanism of the UL4 protein. In this study, fluorescence microscopy was employed to investigate the subcellular localization of UL4 and characterize the transport mechanism in living cells. By constructing a series of deletion mutants fused with enhanced yellow fluorescent protein （EYFP）, the nuclear export signals （NES） of UL4 were for the first time mapped to amino acid residues 178 to 186. In addition, the N-terminal 19 amino acids are identified to be required for the granule-like cytoplasmic pattem of UL4. Furthermore, the UL4 protein was demonstrated to be exported to the cytoplasm through the NES in a chromosomal region maintenance 1 （CRM1）-dependent manner involving RanGTP hydrolysis

Molecular Cloning, Expression and Subcellular Localization of Human Oct-4 Protein

Objective To clone, express, purify human Oct-4 and detect its subcellular localization. Methods Human Oct-4 cDNA was amplified by RT-PCR strategy. Oct-4 protein was induced and expressed in BL21(DE3) strain. Furthermore, the protein was purified with Ni-NTA resin. Subsequently, site-directed mutagenesis of Oct-4 (aa 236-240) was introduced. Finally, the subcellular localization of wide type Oct-4 and mutant Oct-4 was examined by immunofluorescent cytochemistry staining and confocal laser scanning microscope analysis. Results The full length cDNA of human Oct-4 was 1083bp. Human Oct-4 encoded a 55 kd protein by prokaryotic vector in E coli. Compared with pure nuclear localization of wide type Oct-4, mutant Oct-4 was mostly enriched in the cytoplasm. Conclusion The cloning, expression and investigation of subcellular localization of human Oct-4 are basis of studying its biological function.

MOLECULAR CLONING, EXPRESSION AND SUBCELLULAR LOCALIZATION OF HUMAN OCT-4 PROTEIN

Objective To clone, express, purify human Oct-4 and detect its subcellular localization. Methods Human Oct-4 cDNA was amplified by RT-PCR strategy. Oct-4 protein was induced and expressed in BL21(DE3) strain. Furthermore, the protein was purified with Ni-NTA resin. Subsequently, site-directed mutagen-esis of Oct-4 (aa 236 - 240) was introduced. Finally, the subcellular localization of wide type Oct-4 and mutant Oct-4 was examined by immunofluorescent cytochemistry staining and confocal laser scanning microscope analysis. Results The full length cDNA of human Oct-4 was 1083 bp. Human Oct-4 encoded a 55 kd protein by prokaryotic vector in E coli. Compared with pure nuclear localization of wide type Oct-4, mutant Oct-4 was mostly enriched in the cytoplasm. Conclusion The cloning, expression and investigation of subcellular localization of human Oct-4 are basis of studying its biological function.

SGLT2抑制剂联合新活素治疗高血压伴心力衰竭的疗效及对患者TLR4/NF-κB信号通路指标的影响

目的研究钠-葡萄糖协同转运蛋白2(SGLT2)抑制剂(达格列净)联合新活素治疗高血压伴心力衰竭(心衰)的临床效果及对患者外周血单核细胞Toll样受体4/核转录因子-κB(TLR4/NF-κB)信号通路指标的影响。方法前瞻性选取2021年5月至2023年6月郑州大学第一附属医院收治的138例高血压伴心衰患者作为研究对象,采用随机数表法分为对照组、单一组和联合组各46例。对照组接受常规基础治疗,单一组在此基础上接受新活素治疗,联合组在此基础上接受达格列净联合新活素治疗。治疗7 d后比较三组患者的临床疗效,以及治疗前后的心功能[左室收缩末期内径(LVESD)、左室射血分数(LVEF)、心率(HR)]、运动耐力[6 min步行试验距离(6 MWT)]、血压[收缩压(SBP)、舒张压(DBP)]、氧化应激指标[丙二醛(MDA)、过氧化氢酶(CAT)、谷胱甘肽过氧化物酶(GSH-Px)]和TLR4/NF-κB信号通路相关指标[TLR4、NF-κB、白细胞介素-1β(IL-1β)、IL-6、肿瘤坏死因子-α(TNF-α)],同时比较三组患者的不良反应发生情况。结果联合组患者的治疗总有效率为95.65%,明显高于单一组的86.96%和对照组的73.91%,差异均有统计学意义(P<0.05);治疗后,联合组患者的LVEF、6 MWT分别为(43.28±3.16)%、(336.48±32.49)m,明显高于单一组的(40.54±2.68)%、(306.45±40.26)m和对照组的(38.07±2.89)%、(280.69±36.98)m,LVESD、HR分别为(35.29±4.26)mm、(71.34±3.62)次/min,明显低于单一组的(38.75±3.64)mm、(74.25±3.59)次/min和对照组的(42.36±4.05)mm、(76.46±3.98)次/min,且单一组变化幅度大于对照组,差异均有统计学意义(P<0.05);治疗后,联合组患者的SBP、DBP分别为(110.36±5.02)mmHg、(81.42±2.56)mmHg,明显低于单一组的(114.83±4.76)mmHg、(84.39±2.88)mmHg和对照组的(117.25±5.18)mmHg、(86.05±2.62)mmHg,且单一组低于对照组,差异均有统计学意义(P<0.05);治疗后,联合组患者的GSH-Px、CAT分别为(105.24±20.29)U/g·Hb、(148.35±32.46)U/mL,明显高于单一组的(90.35±19.45)U/g·Hb、(125.64±26.49)U/mL和对照组的(84.49±17.32)U/g·Hb、(103.29±25.38)U/mL,MDA为(7.39±2.56)mmol/L,明显低于单一组的(11.35±2.95)mmol/L和对照组的(13.08±2.72)mmol/L,且单一组变化幅度大于对照组,差异均有统计学意义(P<0.05);治疗后,联合组患者的TLR4 mRNA、NF-κB mRNA、IL-1βmRNA、IL-6 mRNA、TNF-αmRNA明显低于单一组和对照组,且单一组低于对照组,差异均有统计学意义(P<0.05);三组患者的不良反应总发生率比较差异无统计学意义(P>0.05)。结论SGLT2抑制剂联合新活素治疗高血压伴心衰能有效改善患者的氧化应激水平,调节TLR4/NF-κB信号通路,恢复患者血压与心功能,临床应用效果显著,且安全性较高。

NLS-KALA-SA纳米粒的制备及细胞核靶向性评价

目的构建由融合肽KALA、硬脂酸(SA)、核定位信号(NLS)组成的细胞核靶向多肽纳米载体(NLSKALA-SA,NKSN)。方法采用Fmoc多肽固相合成法人工合成NLS-KALA-SA多肽纳米载体。结果NLSKALA-SA纳米颗粒呈球形,平均尺寸为(76.4±7.6)mm,Zeta电位为(43.7±5.8)mV。纳米颗粒呈正态分布,粒径分布较窄,多分散度指数(PI<0.3)。细胞摄取实验研究表明,包载香豆素-6(C-6)的NLS-KALA-SA纳米粒子(C-6/NKSN)主要积聚在A549细胞的细胞核中。细胞毒性实验研究表明,在检测浓度为0.01~1000 mg/mL时,NLS-KALA-SA对A549细胞几乎没有细胞毒性。结论NLS-KALA-SA是一种安全无毒且具有跨膜转运和核定位功能的纳米载体,有望成为一种有前景的癌症治疗多肽纳米载体。

Predicting the Nuclear Localization Signals of 107 Types of HPV L1 Proteins by Bioinformatic Analysis

In this study, 107 types of human papillomavirus （HPV） L1 protein sequences were obtained from available databases, and the nuclear localization signals （NLSs） of these HPV L1 proteins were analyzed and predicted by bioinformatic analysis. Out of the 107 types, the NLSs of 39 types were predicted by PredictNLS software （35 types of bipartite NLSs and 4 types of monopartite NLSs）. The NLSs of the remaining HPV types were predicted according to the characteristics and the homology of the already predicted NLSs as well as the general rule of NLSs. According to the result, the NLSs of 107 types of HPV L1 proteins were classified into 15 categories. The different types of HPV L1 proteins in the same NLS category could share the similar or the same nucleocytoplasmic transport pathway. They might be used as the same target to prevent and treat different types of HPV infection. The results also showed that bioinformatic technology could be used to analyze and predict NLSs of proteins.

Application of a nuclear localization signal gene in transgene mice

Efficient gene transfer by cytoplasm co-injec-tion will offer a powerful means for transgenic animals. Us-ing co-injection in cytoplasm, two independent gene con-structs, including bovine a-s1-casein-hG-CSF and a mammal expression vector expressing a nuclear localization signal (mNLS), were introduced into fertilized mouse eggs. The target gene construct was docked into host nucleus probably by the nuclear localization signal. Transgene mice have been obtained at 58% (29/50) of integration ratio. Ex-pression level of the positive transgene mice was detected by Western blotting. Maximal expression of human G-CSF was estimated about 540 mg/L of milk. The expression ratio was up to 75% (9/12). The results here have important practical implications for the generation of mammary gland bioreac-tors and other transgene studies. Co-injection of a target gene with an expression vector of a mammal nuclear localization signal by cytoplasm appears to be a useful, efficient and easy strategy for generating

杆状病毒表达系统中NLS序列对鸭圆环病毒Cap基因表达的影响及其免疫原性研究

为了研究核定位信号肽(Nuclear localization signal,NLS)序列对鸭圆环病毒(duck Circovirus,DuCV)Cap蛋白表达的影响,并探究不同免疫策略下重组蛋白的免疫原性,试验将去除和未去除NLS序列的DuCV Cap基因分别克隆至杆状病毒载体pFastBacⅠ中,通过杆状病毒表达系统进行表达,分析NLS序列对Cap蛋白表达的影响。采用不同的免疫策略,分别以原核表达系统构建的重组蛋白rCap(rCap组)、杆状病毒表达系统构建的rvAc-Cap(rvAc-Cap组)及rCap与rvAc-Cap联合(Prime-Boost组)作为免疫源免疫Balb/c小鼠,并设置PBS对照组,定期采血,检测DuCV IgG抗体水平、淋巴细胞增殖指数(SI)和γ干扰素(IFN-γ)、白细胞介素-2(IL-2)、白细胞介素-4(IL-4)等细胞因子水平,评价其免疫效果。结果表明:利用杆状病毒表达系统成功表达出重组杆状病毒rvAc-Cap和rvAc-NLS-Cap,且去除NLS序列的Cap基因表达水平更高;小鼠免疫重组蛋白rCap后,重组蛋白rCap与重组杆状病毒rvAc-Cap均能够刺激小鼠产生特异性IgG抗体,三免后Prime-Boost组的IgG抗体水平最高,而与其他免疫组差异不显著(P>0.05);三免后各免疫组淋巴细胞增殖指数显著高于PBS对照组,差异显著(P<0.05);各免疫组IFN-γ、IL-2和IL-4水平与PBS对照组比较差异显著(P<0.05),且Prime-Boost组水平最高。说明在杆状病毒表达系统中去除NLS序列可以提高Cap基因的表达;重组杆状病毒rvAc-Cap能够活化小鼠的免疫系统,刺激小鼠机体产生体液免疫与细胞免疫,而Prime-Boost免疫策略有效提高了免疫效果。

马铃薯线粒体靶向表达载体的构建与应用

【目的】植物线粒体基因变异是产生细胞质雄性不育(cytoplasmic male sterility,CMS)的主要原因,利用生物技术是创造CMS不育系的重要手段。通过比较启动子、线粒体转运信号肽(mitochondrial targeting signal peptides,MTS)的不同组合对下游eGFP的表达强弱,来探究最佳马铃薯线粒体靶向表达载体。【方法】选择3个启动子AtUBI10、StUBI10、2×35S和两个线粒体转运信号肽ATPγ与Rf1b进行试验,利用烟草叶片瞬时表达系统和PEG介导马铃薯原生质体转化体系进行靶向载体的表达验证。【结果】六个线粒体靶向表达载体中AtUBI10::ATPγ-eGFP在烟草瞬时表达效果最佳,可准确定位到线粒体,其次为StUBI10::ATPγ-eGFP和2×35S::ATPγ-eGFP;在马铃薯原生质体中载体AtUBI10::ATPγ-eGFP有最佳的表达效果,与烟草中表达结果一致,其次是StUBI10::Rf1b-eGFP和AtUBI10::Rf1b-eGFP,而2×35S启动子的两个载体在原生质体均表达较弱。【结论】启动子AtUBI10与线粒体转运信号肽ATPγ所构建的靶向线粒体载体为最佳组合,可用于马铃薯线粒体基因的相关研究中。

猪圆环病毒2型Cap蛋白核定位信号区抗原表位的鉴定

【目的】猪圆环病毒2型(PCV2)是引起断奶仔猪多系统衰竭综合症(PMWS)的重要病原,其基因组ORF2编码的Cap蛋白为病毒的主要结构蛋白,起保护性抗原作用,对其进行抗原表位鉴定十分必要。【方法】本研究采用杆状病毒表达的重组Cap蛋白作为免疫原制备5株单克隆抗体,通过原核表达系统对ORF2基因进行了截短表达,先行对Cap蛋白抗原表位进行宽幅定位,然后利用合成多肽对Cap抗原表位做精确扫描定位。【结果】5株单抗中有4株针对同一抗原表位,坐落在Cap蛋白N末端核定位信号区,经多肽扫描证实,核心序列为26RPWLVHPRHRY36;另1株单抗(1D2)仅与重组Cap蛋白产生免疫活性反应,对4个分段截短表达的Cap蛋白无免疫活性反应,鉴于该单抗具有中和病毒活性,针对的可能是构象表位。【结论】本研究首次鉴定出位于Cap蛋白核定位信号区的一个抗原表位,为以后Cap蛋白功能及核定位机理的研究奠定基础。

鸽圆环病毒浙江株△Cap基因的克隆与原核表达

根据已发表的鸽圆环病毒(PiCV)序列,在V1ORF保守序列部位设计引物(目的片段长度为629bp),对浙江某鸽养殖场的病料进行PCR扩增检测,获得阳性样品;应用设计的删除核定位信号外壳蛋白基因(△Cap)的引物,扩增获得680bp的△Cap基因,克隆于pMD18-T载体,进行测序;将△Cap基因亚克隆到原核表达载体pET-28a进行融合表达,SDS-PAGE电泳检测发现,△Cap融合蛋白经IPTG诱导后在大肠杆菌中以包涵体形式表达,目的蛋白表达量占菌体总蛋白的22.1%。

核定位信号筛选系统的构建

建立了一酵母克隆系统用于克隆含核定位信号 (NLS)的蛋白质的基因 .用表达转录因子GAL4 DNA结合域 - p53(GAL4- DBD- p53)融合蛋白的质粒转化酵母 HF7c,使 GAL4- DBD- p53可结合于报告基因的启动子但因无转录激活域而不能激活转录 .构建一酵母穿梭载体 ,可表达无NLS的 GAL4转录激活域 -大 T抗原 (GAL4- AD- LT)融合蛋白 .融合蛋白基因的下游插入一多克隆位点 .将 c DNA文库插入多克隆位点后 ,如果 c DNA片段可编码 NLS,则 GAL4- AD- LT分子可进入细胞核 ,并通过 LT与 p53的相互作用而使 GAL4- AD结合于启动子和激活报告基因的转录 .构建了这一克隆系统的各质粒 ,并用绿色荧光蛋白 (GFP)验证了其对核内蛋白和胞浆蛋白的甄别能力 .这一系统将有助于从 c DNA文库中筛选编码带有

核定位信号及其分析策略

真核细胞核膜上的核孔复合体(nuclear pore complex,NPC)是细胞核内外进行物质交换的主要通道,分子量较小的化合物可自由通过NPC或采取被动扩散的方式进入细胞核,而分子量为50kD以上的蛋白质则只能通过主动转运进入细胞核.以这种方式进入细胞核的蛋白质必须在其氨基酸序列上拥有特殊的核定位信号(nuclear localization signal,NLS),以被相应的核转运蛋白(karyopherins)识别.核定位信号具有多样性,包括经典核定位信号(classical NLS,cNLS),内输蛋白β2识别的核定位信号(又称PY模体-NLS)和其它类型的NLS.每一类NLS具有相似的特征,但并不具有完全保守的氨基酸组成.不同的NLS,往往对应着各不相同的核输入机制.而对同一蛋白质来说,也可能同时拥有几个功能性的NLS.研究核定位信号一方面可以帮助揭示新的大分子物质核转运机制,另一方面也有助于发现一些蛋白质的新功能.本文对常见NLS的分类进行了总结,并介绍了两种常用的NLS预测软件及鉴定NLS的一般策略.