scholarly journals Modulation of Human Immunodeficiency Virus Type 1 Protease Autoprocessing by Charge Properties of Surface Residue 69

2009 ◽  
Vol 83 (15) ◽  
pp. 7789-7793 ◽  
Author(s):  
Liangqun Huang ◽  
Jane M. Sayer ◽  
Marie Swinford ◽  
John M. Louis ◽  
Chaoping Chen
Keyword(s):  
Human Immunodeficiency Virus ◽  
Mammalian Cells ◽  
Surface Residue ◽  
Wild Type ◽  
Autocatalytic Processing ◽  
Immunodeficiency Virus ◽  
Folding Defect ◽  
Protease Precursor

ABSTRACT Mature, fully active human immunodeficiency virus protease (PR) is liberated from the Gag-Pol precursor via regulated autoprocessing. A chimeric protease precursor, glutathione S-transferase-transframe region (TFR)-PR-FLAG, also undergoes N-terminal autocatalytic maturation when it is expressed in Escherichia coli. Mutation of the surface residue H69 to glutamic acid, but not to several neutral or basic amino acids, impedes protease autoprocessing in bacteria and mammalian cells. Only a fraction of mature PR with an H69E mutation (PRH69E) folds into active enzymes, and it does so with an apparent Kd (dissociation constant) significantly higher than that of the wild-type protease, corroborating the marked retardation of the in vitro N-terminal autocatalytic processing of TFR-PRH69E and suggesting a folding defect in the precursor.

scholarly journals Changes in Human Immunodeficiency Virus Type 1 Gag at Positions L449 and P453 Are Linked to I50V Protease Mutants In Vivo and Cause Reduction of Sensitivity to Amprenavir and Improved Viral Fitness In Vitro

2002 ◽  
Vol 76 (15) ◽  
pp. 7398-7406 ◽  
Author(s):  
Michael F. Maguire ◽  
Rosario Guinea ◽  
Philip Griffin ◽  
Sarah Macmanus ◽  
Robert C. Elston ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Viral Fitness ◽  
Wild Type Virus ◽  
Wild Type ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT Human immunodeficiency virus type 1 (HIV-1) Gag protease cleavage sites (CS) undergo sequence changes during the development of resistance to several protease inhibitors (PIs). We have analyzed the association of sequence variation at the p7/p1 and p1/p6 CS in conjunction with amprenavir (APV)-specific protease mutations following PI combination therapy with APV. Querying a central resistance data repository resulted in the detection of significant associations (P < 0.001) between the presence of APV protease signature mutations and Gag L449F (p1/p6 LP1′F) and P453L (p1/p6 PP5′L) CS changes. In population-based sequence analyses the I50V mutant was invariably linked to either L449F or P453L. Clonal analysis revealed that both CS mutations were never present in the same genome. Sequential plasma samples from one patient revealed a transition from I50V M46L P453L viruses at early time points to I50V M46I L449F viruses in later samples. Various combinations of the protease and Gag mutations were introduced into the HXB2 laboratory strain of HIV-1. In both single- and multiple-cycle assay systems and in the context of I50V, the L449F and P453L changes consistently increased the 50% inhibitory concentration of APV, while the CS changes alone had no measurable effect on inhibitor sensitivity. The decreased in vitro fitness of the I50V mutant was only partially improved by addition of either CS change (I50V M46I L449F mutant replicative capacity ≈ 16% of that of wild-type virus). Western blot analysis of Pr55 Gag precursor cleavage products from infected-cell cultures indicated accumulation of uncleaved Gag p1-p6 in all I50V viruses without coexisting CS changes. Purified I50V protease catalyzed cleavage of decapeptides incorporating the L449F or P453L change 10-fold and 22-fold more efficiently than cleavage of the wild-type substrate, respectively. HIV-1 protease CS changes are selected during PI therapy and can have effects on both viral fitness and phenotypic resistance to PIs.

scholarly journals Virus Particle Core Defects Caused by Mutations in the Human Immunodeficiency Virus Capsid N-Terminal Domain

2005 ◽  
Vol 79 (3) ◽  
pp. 1470-1479 ◽  
Author(s):  
Isabel Scholz ◽  
Brian Arvidson ◽  
Doug Huseby ◽  
Eric Barklis
Keyword(s):  
Human Immunodeficiency Virus ◽  
Wild Type ◽  
Immunodeficiency Virus ◽  
Order Structures ◽  
Binding Loop ◽  
Hiv 1 ◽  
Cypa Binding

ABSTRACT The N-terminal domains (NTDs) of the human immunodeficiency virus type 1 (HIV-1) capsid (CA) protein have been modeled to form hexamer rings in the mature cores of virions. In vitro, hexamer ring units organize into either tubes or spheres, in a pH-dependent fashion. To probe factors which might govern hexamer assembly preferences in vivo, we examined the effects of mutations at CA histidine residue 84 (H84), modeled at the outer edges of NTD hexamers, as well as a nearby histidine (H87) in the cyclophilin A (CypA) binding loop. Although mutations at H87 yielded infectious virions, mutations at H84 produced assembly-competent but poorly infectious virions. The H84 mutant viruses incorporated wild-type levels of CypA and viral RNAs and showed nearly normal signals in virus entry assays. However, mutant CA proteins assembled aberrant virus cores, and mutant core fractions retained abnormally high levels of CA but reduced reverse transcriptase activities. Our results suggest that HIV-1 CA residue 84 contributes to a structure which helps control either NTD hexamer assembly or the organization of hexamers into higher-order structures.

scholarly journals Relative Replicative Fitness of Human Immunodeficiency Virus Type 1 Mutants Resistant to Enfuvirtide (T-20)

2004 ◽  
Vol 78 (9) ◽  
pp. 4628-4637 ◽  
Author(s):  
Jing Lu ◽  
Prakash Sista ◽  
Françoise Giguel ◽  
Michael Greenberg ◽  
Daniel R. Kuritzkes
Keyword(s):  
Human Immunodeficiency Virus ◽  
Relative Order ◽  
Wild Type ◽  
Resistance Mutations ◽  
Recombinant Viruses ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT Resistance to enfuvirtide (ENF; T-20), a fusion inhibitor of human immunodeficiency virus type 1 (HIV-1), is conferred by mutations in the first heptad repeat of the gp41 ectodomain. The replicative fitness of recombinant viruses carrying ENF resistance mutations was studied in growth competition assays. ENF resistance mutations, selected in vitro or in vivo, were introduced into the env gene of HIV-1NL4-3 by site-directed mutagenesis and expressed in HIV-1 recombinants carrying sequence tags in nef. The doubling time of ENF-resistant viruses was highly correlated with decreasing ENF susceptibility (R 2 = 0.859; P < 0.001). Initial fitness experiments focused on mutants identified by in vitro selection in the presence of ENF (L. T. Rimsky, D. C. Shugars, and T. J. Matthews, J. Virol. 72:986-993, 1998). In the absence of drug, these mutants displayed reduced fitness compared to wild-type virus with a relative order of fitness of wild type > I37T > V38 M > D36S/V38 M; this order was reversed in the presence of ENF. Likewise, recombinant viruses carrying ENF resistance mutations selected in vivo displayed reduced fitness in the absence of ENF with a relative order of wild type > N42T > V38A > N42T/N43K ≈ N42T/N43S > V38A/N42D ≈ V38A/N42T. Fitness and ENF susceptibility were inversely correlated (r = −0.988; P < 0.001). Similar results were obtained with recombinants expressing molecularly cloned full-length env genes obtained from patient-derived HIV-1 isolates before and after ENF treatment. Further studies are needed to determine whether the reduced fitness of ENF-resistant viruses alters their pathogenicity in vivo.

scholarly journals Assembly Properties of Human Immunodeficiency Virus Type 1 Gag-Leucine Zipper Chimeras: Implications for Retrovirus Assembly

2008 ◽  
Vol 83 (5) ◽  
pp. 2216-2225 ◽  
Author(s):  
Rachael M. Crist ◽  
Siddhartha A. K. Datta ◽  
Andrew G. Stephen ◽  
Ferri Soheilian ◽  
Jane Mirro ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Nucleic Acid ◽  
Human Immunodeficiency Virus Type ◽  
Mammalian Cells ◽  
Leucine Zipper ◽  
Chimeric Proteins ◽  
Wild Type ◽  
Particle Assembly ◽  
Immunodeficiency Virus

ABSTRACT Expression of the retroviral Gag protein leads to formation of virus-like particles in mammalian cells. In vitro and in vivo experiments show that nucleic acid is also required for particle assembly. However, several studies have demonstrated that chimeric proteins in which the nucleocapsid domain of Gag is replaced by a leucine zipper motif can also assemble efficiently in mammalian cells. We have now analyzed assembly by chimeric proteins in which nucleocapsid of human immunodeficiency virus type 1 (HIV-1) Gag is replaced by either a dimerizing or a trimerizing zipper. Both proteins assemble well in human 293T cells; the released particles lack detectable RNA. The proteins can coassemble into particles together with full-length, wild-type Gag. We purified these proteins from bacterial lysates. These recombinant “Gag-Zipper” proteins are oligomeric in solution and do not assemble unless cofactors are added; either nucleic acid or inositol phosphates (IPs) can promote particle assembly. When mixed with one equivalent of IPs (which do not support assembly of wild-type Gag), the “dimerizing” Gag-Zipper protein misassembles into very small particles, while the “trimerizing” protein assembles correctly. However, addition of both IPs and nucleic acid leads to correct assembly of all three proteins; the “dimerizing” Gag-Zipper protein also assembles correctly if inositol hexakisphosphate is supplemented with other polyanions. We suggest that correct assembly requires both oligomeric association at the C terminus of Gag and neutralization of positive charges near its N terminus.

scholarly journals Roles of Pr55gag and NCp7 in tRNA3Lys Genomic Placement and the Initiation Step of Reverse Transcription in Human Immunodeficiency Virus Type 1

2000 ◽  
Vol 74 (22) ◽  
pp. 10796-10800 ◽  
Author(s):  
Shan Cen ◽  
Ahmad Khorchid ◽  
Juliana Gabor ◽  
Liwei Rong ◽  
Mark A. Wainberg ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Reverse Transcription ◽  
Viral Rna ◽  
Wild Type ◽  
Immunodeficiency Virus ◽  
Initiation Step

ABSTRACT To study in vivo tRNA3 Lys genomic placement and the initiation step of reverse transcription in human immunodeficiency virus type 1, total viral RNA isolated from either wild-type or protease-negative (PR−) virus was used as the source of primer tRNA3 Lys/genomic RNA templates in an in vitro reverse transcription assay. At low dCTP concentrations, both the rate and extent of the first nucleotide incorporated into tRNA3 Lys, dCTP, were lower with PR− than with wild-type total viral RNA. Transient in vitro exposure of either type of primer/template RNA to NCp7 increased PR− dCTP incorporation to wild-type levels but did not change the level of wild-type dCTP incorporation. Exposure of either primer/template to Pr55 gag had no effect on initiation. These results indicate that while Pr55 gag is sufficient for tRNA3 Lys placement onto the genome, exposure of this complex to mature NCp7 is required for optimum tRNA3 Lys placement and initiation of reverse transcription.

scholarly journals The 5′ and 3′ TAR Elements of Human Immunodeficiency Virus Exert Effects at Several Points in the Virus Life Cycle

1998 ◽  
Vol 72 (11) ◽  
pp. 9217-9223 ◽  
Author(s):  
Atze T. Das ◽  
Bep Klaver ◽  
Ben Berkhout
Keyword(s):  
Human Immunodeficiency Virus ◽  
Life Cycle ◽  
Reverse Transcription ◽  
Wild Type ◽  
Rna Packaging ◽  
Virus Life Cycle ◽  
Activation Of Transcription ◽  
Immunodeficiency Virus

ABSTRACT The human immunodeficiency virus type 1 RNA genome contains a terminal repeat (R) sequence that encodes the TAR hairpin motif, which has been implicated in Tat-mediated activation of transcription. More recently, a variety of other functions have been proposed for this structured RNA element. To determine the replicative roles of the 5′ and 3′ TAR hairpins, we analyzed multiple steps in the life cycle of wild-type and mutant viruses. A structure-destabilizing mutation was introduced in either the 5′, the 3′, or both TAR motifs of the proviral genome. As expected, opening of the 5′ TAR hairpin caused a transcription defect. Because the level of protein expression was not similarly reduced, the translation of this mRNA was improved. No effect of the 3′ hairpin on transcription and translation was measured. Mutations of the 5′ and 3′ hairpin structures reduced the efficiency of RNA packaging to similar extents, and RNA packaging was further reduced in the 5′ and 3′ TAR double mutant. Upon infection of cells with these virions, a reduced amount of reverse transcription products was synthesized by the TAR mutant. However, no net reverse transcription defect was observed after correction for the reduced level of virion RNA. This result was confirmed in in vitro reverse transcription assays. These data indicate that the 5′ and 3′ TAR motifs play important roles in several steps of the replication cycle, but these structures have no significant effect on the mechanism of reverse transcription.

scholarly journals Mutational Analysis of the Human Immunodeficiency Virus Type 1 Vpu Transmembrane Domain That Promotes the Enhanced Release of Virus-Like Particles from the Plasma Membrane of Mammalian Cells

1998 ◽  
Vol 72 (2) ◽  
pp. 1270-1279 ◽  
Author(s):  
Mousumi Paul ◽  
Suparna Mazumder ◽  
Nicholas Raja ◽  
M. Abdul Jabbar
Keyword(s):  
Amino Acids ◽  
Human Immunodeficiency Virus ◽  
Plasma Membrane ◽  
Human Immunodeficiency Virus Type ◽  
Hela Cells ◽  
Mammalian Cells ◽  
Transmembrane Domain ◽  
Wild Type ◽  
Immunodeficiency Virus

ABSTRACT Human immunodeficiency virus type 1 Vpu is a multifunctional phosphoprotein composed of the N-terminal transmembrane (VpuTM) and C-terminal cytoplasmic domains. Each of these domains regulates a distinct function of the protein; the transmembrane domain is critical in virus release, and phosphorylation of the cytoplasmic domain is necessary for CD4 proteolysis. We carried our experiments to identify amino acids in the VpuTM domain that are important in the process of virus-like particle (VLP) release from HeLa cells. VLPs are released from the plasma membrane of HeLa cells at constitutive levels, and Vpu expression enhanced the release of VLPs by a factor of 10 to 15. Deletion of two to five amino acids from both N- and C-terminal ends or the middle of the VpuTM domain generated mutant Vpu proteins that have lost the ability to enhance VLP release. These deletion mutants have not lost the ability to associate with the wild-type or mutant Vpu proteins and formed complexes with equal efficiency. They were also transported normally to the Golgi complex. Furthermore, a Vpu protein having the CD4 transmembrane and Vpu cytoplasmic domains was completely inactive, and Vpu proteins harboring hybrid Vpu-CD4 TM domains were also defective in the ability to enhance the release of VLPs. When tested for functional complementation in cotransfected cells, two inactive proteins were not able to reconstitute Vpu activity that enhances the release of Gag particles. Coexpression of functional CD4/Vpu hybrids or wild-type Vpu with inactive mutant CD4/Vpu proteins revealed that mutations in the VpuTM domain could dominantly interfere with Vpu activity in Gag release. Taken together, these results demonstrated that the structural integrity of the VpuTM domain is critical for Vpu activity in the release of VLPs from the plasma membrane of mammalian cells.

scholarly journals Characterization of a Novel Human Immunodeficiency Virus Type 1 Protease Inhibitor, A-790742

2008 ◽  
Vol 52 (4) ◽  
pp. 1337-1344 ◽  
Author(s):  
Tatyana Dekhtyar ◽  
Teresa I. Ng ◽  
Liangjun Lu ◽  
Sherie Masse ◽  
David A. DeGoey ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Protease Inhibitor ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
In Vitro Selection ◽  
Wild Type ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT A-790742 is a potent human immunodeficiency virus type 1 (HIV-1) protease inhibitor, with 50% effective concentrations ranging from 2 to 7 nM against wild-type HIV-1. The activity of this compound is lowered by approximately sevenfold in the presence of 50% human serum. A-790742 maintained potent antiviral activity against lopinavir-resistant variants generated in vitro as well as against a panel of molecular clones containing proteases derived from HIV-1 patient isolates with multiple protease mutations. During in vitro selection, A-790742 selected two primary mutations (V82L and I84V) along with L23I, L33F, K45I, A71V/A, and V77I in the pNL4-3 background and two other mutations (A71V and V82G) accompanied by M46I and L63P in the HIV-1 RF background. HIV-1 pNL4-3 clones with a single V82L or I84V mutation were phenotypically resistant to A-790742 and ritonavir. Taking these results together, A-790742 displays a favorable anti-HIV-1 profile against both the wild type and a large number of mutants resistant to other protease inhibitors. The selection of the uncommon V82L and V82G mutations in protease by A-790742 suggests the potential for an advantageous resistance profile with this protease inhibitor.

scholarly journals Vaccine-Induced Immune Responses in Rodents and Nonhuman Primates by Use of a Humanized Human Immunodeficiency Virus Type 1 pol Gene

2002 ◽  
Vol 76 (1) ◽  
pp. 185-194 ◽  
Author(s):  
Danilo R. Casimiro ◽  
Aimin Tang ◽  
Helen C. Perry ◽  
Romnie S. Long ◽  
Minchun Chen ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
T Cells ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Mammalian Cells ◽  
Synthetic Gene ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT A synthetic gene consisting of the reverse transcriptase (RT) and integrase (IN) domains of human immunodeficiency virus type 1 (HIV-1) pol was constructed using codons most frequently used in humans. The humanized pol gave dramatically improved levels of Rev-independent, in vitro protein production in mammalian cells and elicited much stronger cellular immunity in rodents than did virus-derived gene. Specifically, BALB/c mice were immunized with plasmids and/or recombinant vaccinia virus constructs expressing the synthetic gene. High frequencies of Pol-specific T lymphocytes were detected in these animals by the gamma interferon enzyme-linked immunospot assay against pools of short overlapping peptides. Characterization of the stimulatory peptides from these pools indicates that the optimized gene constructs are able to effectively activate both CD4+ and CD8+ T cells. Immunization of rhesus macaques with DNA vaccines expressing the humanized pol coupled to a human tissue plasminogen activator leader sequence led to pronounced in vitro cytotoxic T-lymphocyte killing activities and enhanced levels of circulating Pol-specific T cells, comparable to those observed in HIV-1-infected human subjects. Thus, optimizing the immunogenic properties of HIV-1 Pol at the level of the gene sequence validates it as an antigen and provides an important step toward the construction of a potent pol-based HIV-1 vaccine component.

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