人免疫缺陷病毒1型TAT蛋白点突变对其反式激活作用的影响

不同免疫缺陷病毒（ＨＩＶ－１,ＨＩＶ－２和ＳＩＶ）的Ｔａｔ均有３个高度保守的结构域：Ｃｙｓ富集域、核心域和碱性氨基酸富集域。用ＰＣＲ定点突变法在ＨＩＶ－１ Ｔａｔ蛋白的这些区域引入单氨基酸或多氨基酸突变;构建了以ＨＩＶ－１ ＬＴＲ－１５８到＋８０区域为启动子,含有不同突变点的突变Ｔａｔ基因表达质粒;以荧光酶基因为报告基因,瞬时共转染Ｊｕｒｋａｔ细胞：分析不同氨基酸突变对Ｔａｔ的反式激活作用的影响。     

人免疫缺陷病毒1型TAT突变蛋白及反义TAT RNA对TAT反式激活作用的抑制

Ｔａｔ是人免疫缺陷病毒（ＨＩＶ）基因组编码的反式激活因子,突变分析表明它含有几个重要的功能域。为寻找控制ＨＩＶ复制的途径,构建了以ＨＩＶ－１ＬＴＲ（－１５８－＋８０）为启动子的Ｔａｔ ｃＤＮＡ全长反义表达质粒ｐＡＳ－Ｔａｔ,并用已经构建的ＨＩＶ ＬＴＲ－１５８到＋８０为启动子,具有不同突变点的突变Ｔａｔ基因表达质粒,以荧光酶基因为报告基因,共转染Ｊｕｒｋａｔ细胞,结果发现无论是反义Ｔａｔ表达质粒还     

多聚TAR-CoreRNA诱饵对人免疫缺陷病毒1型Tat蛋白活性的抑制作用

为了抑制Ｔａｔ蛋白的反式激活作用,在细胞内大量表达外源ＴＡＲＲＮＡ使其与Ｔａｔ蛋白结合,从而竞争性抑制其与ＨＩＶ－１ＬＴＲ的ＴＡＲＲＮＡ元件结合．构建了以ＨＩＶ－１ＬＴＲＹＬ１５８（－１５８～＋１８０）为启动子,分别含有４,８和１５个拷贝的ＴＡＲ－ＣｏｒｅＲＮＡ诱饵（ｄｅｃｏｙ）表达质粒;以荧光酶基因为报告基因,检测了瞬时共转染体系中含不同拷贝数的ＴＡＲ－ＣｏｒｅＤＮＡ转录产物对Ｔａｔ蛋白反式激活作用的影响．结果证明,ＴＡＲ－ＣｏｒｅＲＮＡ诱饵对Ｔａｔ蛋白活性具有很强的抑制作用,其抑制程度与ＴＡＲ－ＣｏｒｅＤＮＡ串联体的拷贝数有关．     

HIV－1反式激活因子（Tat）作用机理的研究进展

ＨＩＶ－１反式激活因子（Ｔａｔ）作用机理的研究进展梁臣,耿运琪（南开大学生命科学学院,天津３０００７１）关键词ＨＩＶ－１,Ｔａｔ,ＴＡＲ人免疫缺陷病毒－１（ＨＩＶ－１）属反转录病毒科,慢病毒亚科,为艾滋病的重要病原体。该病毒可长期潜伏于人体内,但在某...     

Tat蛋白及其内化作用

人类免疫缺陷病毒 1型的复制受反式激活蛋白 (ｔｒａｎｓ ａｃｔｉｖａｔｉｎｇｐｒｏｔｅｉｎ ,Ｔａｔ)的调节。Ｔａｔ蛋白是一个小型蛋白 ,其分子大小依ＨＩＶ 1病毒的品系不同而有所差异 ,从 86到1 30个氨基酸残基不等[1] ,它由两个外显子编码。就 1 0 1个氨基酸的Ｔａｔ蛋白而言[2 ] ,第一个外显子编码 1～ 72氨基酸 ,第二个外显子编码 73～ 1 0 1氨基酸。在细胞内 ,Ｔａｔ蛋白对病毒基因的转录有重要作用。ＨＩＶ 1病毒的ｍＲＮＡ 5′端有一段序列叫做反式激活反应区域 (ｔｒａｎｓ ａｃｔｉｖａｔｉｏｎ ｒｅｓｐｏｎｓｉｖｅｒｅｇｉ…     

树Ju免疫细胞体外感染Ⅰ型人免疫缺陷病毒的实验研究

至今可以感染Ⅰ型人免疫缺陷病毒（ＨＩＶ－１）的动物只有黑猩猩和长臂猿,这严重阻碍了ＨＩＶ－１的疫苗研究和治疗研究。因此,寻找新的可以感染ＨＩＶ－１的动物模型成为十分迫切的课题。已知树Ｊu对许多重要的医学病毒易感,为了探讨树Ｊu是否可以感染ＨＩＶ－１,利用不同辅助受体的５种ＨＩＶ－１病毒株。体外感染云南野生成年树Ju的淋巴细胞和单核／巨噬细胞;同时还用这些病毒感染人外周血淋巴细胞或单核细胞。然后用ＲＴ－ＰＣＲ、ＰＣＲ和流式细胞术分别进行了检测,用ＲＴ－ＰＣＲ方法未检测到感染上清中有病毒粒子的存在,用ＰＣＲ法未能发现树Ｊu的这些免疫细胞中有前病毒ＤＮＡ,用流式细胞术也未能在这些感染ＨＩＶ－１的树Ｊu细胞的表面检测到特异抗原;而感染ＨＩＶ－１的人免疫细胞均为阳性结果。实验结果表明树Ju的这些免疫细胞在体外未能感染上ＨＩＶ－１,可能的原因是树Ｊu的这些免疫细胞的ＨＩＶ－１受体（ＣＤ４）和辅助受体（ＣＣＲ５或ＣＸＣＲ４）与人的免疫细胞胞差别较大。     

ＣＣＲ５与ＨＩＶ—１感染的分子机制研究进展

趋化因子受体５（ＣＣＲ５）作为一个辅助受体在ＨＩＶ－１进入巨噬细胞的过程中发挥重要作用。在不同人种中，ＣＣＲ５存在天然的突变基因型，其中包括纯合子和杂合子基因型，它们对ＨＩＶ－１的易感性也各不相同，实验室中膜外袢的突变、缺失突变、插入及膜内基元的信号转导研究从分子水平揭示了一些氨基酸和空间结构对辅助受体的功能起关键性的作用，这对深入了解ＨＩＶ－１与受体作用的分子机制，为寻找有效的阻断途径无疑是必需的和重要的。     

人源单克隆抗人免疫缺陷病毒1型抗体Fab段基因的获得

应用噬苏体抗体库技术有效地筛选出了多株抗ＨＩＶ－１人源单克隆抗体。以逆转录聚合酶链反应（ＲＴ－ＰＣＲ）从ＨＩＶ－１感染者外周血淋巴细胞中扩增抗体轻重链可变区基因,插入载体ｐＣＯＭＢ３,建立噬菌体抗体库。分别以ＨＩＶ－１ｇｐ１２０和ｇｐ１６０为固相抗原,经过多轮筛选,从中获得了多株抗ＨＩＶ－１ｇｐ４１、ｇｐ１２０和ｇｐ１６０的单克隆抗体Ｆａｂ段基因。抗ＨＩＶ特异性噬菌体抗体随抗体库的筛选高度富集,抗     

HIV—1抗体阳性血浆中HIV—1病毒基因分型研究

为了解ＨＩＶ抗体阳性血浆中的ＨＩＶ１病毒基因亚型的情况,应用逆转录ＰＣＲ和ＤＮＡ序列测定技术,对６份获自高危人群的抗ＨＩＶ１阳性血浆进行序列分析和基因亚型分型的研究,结果表明均属ＨＩＶ１Ｂ亚型。Ｖ３环氨基酸序列分析指出这些ＨＩＶ１Ｂ亚型病毒株与泰国ＨＩＶ１Ｂ亚型病毒株核苷酸和氨基酸序列相似;同时发现ＨＩＶ１ｃＤＮＡ和氨基酸序列均相同,推测这６份标本可能来自同时感染同一株ＨＩＶ病毒的感染者。本研究对了解高危人群中ＨＩＶ１流行的遗传变异和ＨＩＶ１亚型病毒株的分子流行病分析具有一定的意义。     

细胞内抗体在HIV-1感染及爱滋病治疗中的应用

ＨＩＶ1是慢病毒亚家族的成员,是ＡＩＤＳ的病因。像其它逆转录病毒一样,ＨＩＶ1基因组包含ｐｏｌ(聚合酶)、ｅｎｖ(包膜)结构基因,也编码Ｒｅｖ(毒粒蛋白调节子)、Ｔａｔ(反式激活蛋白)等调节蛋白。抗ＨＩＶ1细胞内抗体由细胞合成并导向其结合靶ＨＩＶ1蛋白和发挥抑制功能的细胞隔室。这些内抗体主要瞄准病毒生命周期中必需的蛋白质。1.包膜糖蛋白(ｅｎｖｅｌｏｐｅｇｌｙｃｏｐｒｏｔｅｉｎ)ＨＩＶ1包膜糖蛋白是作为ｇｐ160前体合成的,并在高尔基复合体上分裂为成熟的ｇｐ120/41蛋白。ｇｐ120与ＣＤ4在细胞表面和细胞内的相互作用不仅对病…     

Multiple functional domains of Tat, the trans-activator of HIV-1, defined by mutational analysis.

The tat gene of HIV-1 is a potent trans-activator of gene expression from the HIV long terminal repeat (LTR). To define the functionally important regions of the product of the tat gene (Tat) of HIV-1, deletion, linker insertion and single amino acid substitution mutants within the Tat coding region of strain SF2 were constructed. The effect of these mutations on trans-activation was assessed by measuring the expression of the bacterial chloramphenicol acetyltransferase (CAT) reporter gene linked to the HIV-LTR. These studies have revealed that four different domains of the protein that map within the N-terminal 56 amino acid region are essential for Tat function. In addition to the essential domains, an auxiliary domain that enhances the activity of the essential region has also been mapped between amino acid residues 58 and 66. One of the essential domains maps in the N-terminal 20 amino acid region. The other three essential domains are highly conserved among the various strains of HIV-1 and HIV-2 as well as simian immunodeficiency virus (SIV). Of the conserved domains, one contains seven Cys residues and single amino acid substitutions for several Cys residues indicate that they are essential for Tat function. The second conserved domain contains a Lys X Leu Gly Ile X Tyr motif in which the Lys residue is essential for trans-activation and the other residues are partially essential. The third conserved domain is strongly basic and appears to play a dual role. Mutants lacking this domain are deficient in trans-activation and in efficient targeting of Tat to the nucleus and nucleolus. The combination of the four essential domains and the auxiliary domain contribute to the near full activity observed with the 101 amino acid Tat protein.     

Functional comparison of the basic domains of the Tat proteins of human immunodeficiency virus types 1 and 2 in trans activation.

The trans-activator Tat proteins coded by human immunodeficiency virus type 1 (HIV-1) and HIV-2 appear to be similar in structure and function. However, the Tat protein of HIV-2 (Tat2) activates the HIV-1 long terminal repeat (LTR) less efficiently than Tat1 (M. Emerman, M. Guyader, L. Montagnier, D. Baltimore, and M. A. Muesing, EMBO J. 6:3755-3760, 1987). To determine the functional domain of Tat2 which contributes to this incomplete reciprocity, we have carried out domain substitution between Tat1 and Tat2 by exchanging the basic domains involved in Tat interaction with its target trans-activation-response (TAR) RNA structure. Our results indicate that Tat1 proteins containing substitutions of either 8 or 14 amino acids of the basic domain of Tat2 exhibited reduced trans activation of the HIV-1 LTR by about 1/20 or one-fourth the level induced by wt Tat1. In contrast, Tat2 containing a substitution of the 9-amino-acid basic domain of Tat1 trans activated HIV-1 LTR like native Tat1. A substitution of the highly conserved core domain of Tat2 with that of Tat1 did not have any significant effect on trans activation of the HIV-1 LTR. These results indicate that the basic domain of Tat2 contributes to its inefficient trans activation of the HIV-1 LTR. Mutation of an acidic residue (Glu) located between the core domain and the Arg-rich basic domain of Tat2 at position 77 to a Gly residue increased the activity of Tat2 substantially. These results further suggest that the presence of an acidic residue (Glu) adjacent to Arg-rich sequences may at least partially contribute to the reduced activity of the Tat2 basic domain.     

Trans-dominant Tat mutants with alterations in the basic domain inhibit HIV-1 gene expression

The Tat protein of the human immunodeficiency virus type 1 (HIV-1) is required for efficient viral gene expression. By means of mutational analyses, several domains of the Tat protein that are required for complete activation of HIV-1 gene expression have been defined. These include an amino-terminal activating domain, a cysteine-rich dimerization domain, and a basic domain important in the binding of Tat to the trans-activation response element (TAR) and in Tat nuclear localization. Recently, we described a mutation, known as delta tat, which resulted in a protein with a truncated basic domain. This protein had a "trans-dominant" phenotype in that it inhibited wild-type Tat activation of the HIV-1 LTR. To further characterize the requirements for generating a Tat trans-dominant phenotype, we constructed a variety of Tat proteins with truncations or substitutions in the basic domain. A number of these proteins showed a trans-dominant phenotype. These Tat mutants also inhibited activation of the HIV-1 LTR by a protein composed of Tat fused to the prokaryotic R17 (phage MS2) RNA-binding protein in which the R17 recognition element was inserted in the HIV-1 LTR in place of TAR. Thus, an intact TAR element was not required for this inhibition. We also studied the cellular localization of Tat and a trans-dominant Tat mutant by means of immunofluorescence staining with the use of antibodies reactive to different domains of the Tat protein. The results indicated that Tat becomes localized predominantly in the nucleus both in the presence and absence of the trans-dominant Tat construct, suggesting that the trans-dominant mutant does not inhibit Tat nuclear localization. These studies further define the requirements for the creation of trans-dominant Tat mutants, and suggest that the mechanism of trans-dominant Tat inhibition may be either the formation of an inactive complex between wild-type and mutant Tat or sequestration of cellular factors involved in regulating HIV-1 gene expression.     

Human chromosome 12 is required for optimal interactions between Tat and TAR of human immunodeficiency virus type 1 in rodent cells.

Levels of trans activation of the human immunodeficiency virus type 1 long terminal repeat (HIV-1 LTR) by the virally encoded transactivator Tat show marked species-specific differences. For example, levels of transactivation observed in Chinese hamster ovary (CHO) rodent cells are 10-fold lower than those in human cells or in CHO cells that contain the human chromosome 12. Thus, the human chromosome 12 codes for a protein or proteins that are required for optimal Tat activity. Here, the function of these cellular proteins was analyzed by using a number of modified HIV-1 LTRs and Tats. Neither DNA-binding proteins that bind to the HIV-1 LTR nor proteins that interact with the activation domain of Tat could be implicated in this defect. However, since species-specific differences were no longer observed with hybrid proteins that contain the activation domain of Tat fused to heterologous RNA-binding proteins, optimal interactions between Tat and the trans-acting responsive RNA (TAR) must depend on this factor(s).