[tp widget="default/tpw_default.php"]

what proteins come packaged in hiv

what proteins come packaged in hiv

what proteins come packaged in hiv插图

ThePol proteinof human immunodeficiency virus type 1 (HIV-1) harbours the viral enzymes critical for viral replication; protease (PR),reverse transcriptase (RT),and integrase (IN).Author:Melissa K Hill, Gilda Tachedjian, Johnson MakPublish Year:2005

How many proteins does HIV encode?

The genome of human immunodeficiency virus (HIV) encodes 8 viral proteins playing essential roles during the HIV life cycle. HIV-1 is composed of two copies of noncovalently linked, unspliced, positive-sense single-stranded RNA enclosed by a conical capsid composed of the viral protein p24, typical of lentiviruses.

Do human proteins protect against HIV infection?

The second line of protection against R5- and X4-tropic HIV is provided by the TRIM5α-HRH protein, which binds virus capsids after the virus enters the cell.

What are the accessory proteins of HIV?

HIV-1 replicates actively in a variety of cells by encoding several regulatory (Tat and Rev) and accessory (Vpr, Vif, Vpu, and Nef) proteins. Accessory proteins, thought initially to be dispensable for infection, have now been shown to be important for efficient infection in vivo.

What is the best diet for HIV patients?

Antioxidant-rich fruits and vegetables must be consumed in plenty as they help boost immunity.Omega-3 fatty acids are a must. …Proteins are a must but stick to a low-fat protein diet.Whole grain products like barley,brown rice,quinoa,cereals and whole wheat breads must be consumed regularly.More items…

What is the env of HIV?

Env extends from the surface of the HIV virus particle. The spike-shaped protein is “trimeric” — with 3 identical molecules, each with a cap-like region called glycoprotein 120 (gp120) and a stem called glycoprotein 41 (gp41) that anchors Env in the viral membrane. Only the functional portions of Env remain constant, …

What is the target of HIV?

The viral surface protein known as Env is a major target for potential HIV vaccines. One challenge in developing a vaccine is that Env can mutate rapidly. These changes to the protein’s surface help it to evade the immune system. The surface of the Env protein is also protected by a coat of sugar molecules that helps shield it from …

What is the protein that enables HIV to enter the body?

This model shows a birds-eye view of the trimeric structure of Env, a protein on the HIV surface that enables it to infect cells. Scripps Research Institute. Researchers have developed a more detailed picture of the protein largely responsible for enabling HIV to enter human immune cells and cause infection.

How many people are affected by HIV?

HIV, the virus that causes AIDS, infects more than 34 million people worldwide. Once in the body, HIV attacks and destroys immune cells. Current treatment with antiretroviral therapy helps to prevent the virus from multiplying, thus protecting the immune system. Despite recent advances in treatment, scientists haven’t yet designed a vaccine that protects people from HIV.

Who used cryo-electron microscopy to study the Env structure?

An NCI research team led by Dr. Sriram Subramaniam used cryo-electron microscopy to examine the Env structure. The study appeared on October 23, 2013, in Nature Structural and Molecular Biology.

What are the genes that are involved in HIV?

Structural gene (env,gag and pol), regulatory gene (tat,rev,nef,vif,vpr and vpu in HIV-I and vpx in HIV-2)

What is the regulatory gene?

Regulatory gene: i. Tat gene: ( transactivator of transcription) It encodes transactivator protein (P14) which promotes the transcription of viral genome. ii. Rev gene: (regulatory of expression of viral protein) It encodes Rev protein (P19) and promotes the expression of viral structural proteins. iii.

What is the gag gene?

Gag gene encodes the precursor protein P55 which is cleaved by viral protease (P10) to form matrix protein (P17), Capsid protein (P24) and Nuncleocapsod protein (P7 & P9). Gag gene helps to form core of virus.

What is the structure of HIV?

Structure and properties of HIV. HIV is a spherical virus of about 90 nm in diameter. HIV is enveloped virus. The envelope is a lipid bilayer surrounding the viral matrix, which is derived from host cell membrane during budding. Below the envelope, there is an icosahedral shell called matrix (P17).

What is the matrix of HIV?

Below the envelope, there is an icosahedral shell called matrix (P17). The core consists of cylindrical capsid (P24) which surrounds the genome. HIV is ss RNA virus. The genome consists of two identical copies of +SS RNA and protein which are linked at their 5’ end.

How many copies of RNA are there in HIV?

HIV has two identical copies of +SS RNA genome. The genome consists of 3 structural gene and 6 regulatory gene.

Which cells does a symlink regulate?

It down regulates the expression of CD4 cells, macrophage and MHC-II.

What is the HIV envelope?

Instead, when HIV leaves a host cell it takes part of that cell’s plasma membrane with it. That bit of membrane becomes the HIV envelope. However, the HIV envelope isn’t only made up of components from the host. It is also made up of HIV envelope proteins. HIV envelope proteins include gp 41, gp 120, and gp 160. GP stands for "glycoprotein".

Why are envelope proteins important?

HIV envelope proteins have an important role in HIV entry and infectivity. They are also potentially quite important in prevention and treatment. However, interestingly, the topic of HIV envelope proteins also often comes up in discussions of HIV testing.

What is the protein that keeps GP 120 attached to the viral envelope?

Gp 41 is also the protein that keeps gp 120 attached to the viral envelope. It sits in the membrane and binds to gp 120. GP 120 doesn’t attach to the envelope directly. GP 160 isn’t actually a third HIV envelope protein. Instead, gp 160 is the precursor of gp 120 and gp 41. The larger protein is coded for by the env (envelope) gene.

What is the GP of HIV?

HIV envelope proteins include gp 41, gp 120, and gp 160. GP stands for "glycoprotein". Glycoproteins have carbohydrate, or sugar, components as well as a protein backbone. The number after the gp refers to the proteins’ length.

What to do if you are participating in a HIV trial?

If you do participate in an HIV vaccine trial, tell your healthcare provider. You should also keep careful records of your participation. It is possible that routine HIV testing procedures will no longer be accurate for you.

Why is GP 41 important?

In addition to gp 120, gp 41 is also important in assisting HIV’s entry into host cells. It helps the viral membrane and the cell membrane fuse. This is a critical part of the infection process. The fusion of the two membranes is the first step towards releasing the viral RNA into the cell for replication.

Can HIV be false positive?

There are also concerns about how HIV vaccine trials may affect testing routines. The growing number of people who have participated in these trials could lead to more false positive HIV antibody tests. Vaccines are usually designed to cause the body to make antibodies against specific proteins, such as the HIV envelope proteins. Since those antibodies are exactly what non-RNA HIV tests look for, it could lead to a false positive. This is one thing that saying someone can only be positive if they also produce antibodies to core proteins may help prevent.

What mutation abolishes VIF incorporation into virions?

Mutation of the nucleocapsid zinc finger domain abolishes Vif incorporation into virions. (A) HeLa cells were transiently transfected with plasmid DNAs encoding wild-type HIV-1 (pNL4-3) or a nucleocapsid zinc finger mutant of NL4-3 (pDB653). Virus-containing supernatants were harvested 48 h after transfection, concentrated, and subjected to 10 to 60% linear sucrose gradient centrifugation. Individual gradient fractions were collected and subjected to immunoblotting using an HIV-positive patient serum (APS) or a Vif-specific antiserum (α-Vif). (B) HeLa cells were transfected with the Vif expression vector pNL-A1 (lanes a) or contransfected with pNL-A1 plus pNL4-3 (lanes b) or the zinc finger mutant pDB653 (lanes c). Virus-containing supernatants were harvested 48 h after transfection and pelleted through a cushion of 20% sucrose. Cell lysates and viral pelleted fractions were subjected to immunoblot analysis using an HIV-positive patient serum (APS) or a Vif-specific antiserum (α-Vif). (C) Bands corresponding to Vif in panel B were quantified by densitometric scanning, and the proportion of Vif identified in the pooled gradient fractions was calculated as percentage of total intra- and extracellular Vif.

How to quantify the impact of the NC zinc finger mutations on VIF packaging?

To quantify the impact of the NC zinc finger mutations on Vif packaging, we calculated the ratio of incorporation efficiency by comparing the relative amounts of intracellular versus intravirion Vif. To rule out possible differences in the Vif expression levels between NL4-3 and pDB653 variants, in this experiment Vif was expressed in transfrom the Vif expression plasmid pNL-A1, which does not produce virus particles (62). Thus, HeLa cells were cotransfected with pNL-A1 along with pNL4-3 (Fig. ?(Fig.4B,4B, lanes b) or pDB653 plasmid DNAs (Fig. ?(Fig.4B,4B, lanes c). As a control, HeLa cells were transfected with pNL-A1 plasmid DNA alone (Fig. ?(Fig.4B,4B, lanes a). Cell-free supernatants were harvested 48 h after transfection and subjected to centrifugation through a 20% sucrose cushion. Pelleted material was solubilized in sample buffer. Aliquots of the cell lysates (5% of total) and viral pellets (20% of total) were separated by SDS-PAGE and analyzed by immunoblotting using an HIV-positive patient serum (Fig. ?(Fig.4B,4B, APS) or a Vif-specific antiserum (Fig. ?(Fig.4B,4B, α-Vif). Bands corresponding to intra- and extracellular Vif were quantified by densitometric scanning, and the amount of Vif in the pooled gradient fractions was calculated as a percentage of total intra- and extracellular Vif (Fig. ?(Fig.4C).4C). As can be seen in Fig. ?Fig.4C,4C, approximately 4% of total Vif was found in pooled gradient fractions from pNL-A1-transfected cells. This presumably reflects the level of nonspecific association of Vif with secreted membrane vesicles. In contrast, more than 10% of Vif was found in NL4-3 virus preparations. Importantly, the amount of Vif identified in NC zinc finger mutant virus preparations was reduced to near background levels (Fig. ?(Fig.4C,4C, compare pNL-A1 and pDB653) despite similar levels of intracellular Vif (Fig. ?(Fig.4B,4B, compare lanes b and c) and comparable levels of extracellular virus. Similar results were observed with a separate nucleocapsid zinc finger mutant, pRB73-B-H23C/H44C (not shown) (27). Thus, mutation of the NC zinc finger domains blocks the association of Vif with HIV particles independently of the intracellular expression levels.

How is VIF packaged?

Human Immunodeficiency Virus Type 1 Vif Protein Is Packaged into the Nucleoprotein Complex through an Interaction with Viral Genomic RNA

What is the role of VIF in HIV?

The human immunodeficiency virus type 1 (HIV-1) Vif protein plays an important role in regulating virus infectivity (20, 62). The lack of a functional Vif protein results in the production of virions with reduced or abolished infectivity (20, 35, 62). This effect of Vif on virus infectivity is producer cell dependent and can vary by several orders of magnitude (2, 6, 7, 19, 20, 22, 35, 51, 62, 66). Virus replication in nonpermissive cell types such as H9 is strictly dependent on Vif, while Vif-defective viruses can replicate efficiently in permissive hosts such as Jurkat cells. The cellular factors determining the requirement for Vif are currently not known. Results from heterokaryon analyses which involved the fusion of restrictive with permissive cell types suggest the presence of an inhibitory factor in restrictive cell types (41, 54). However, the identity of the proposed inhibitory factor and its mode of action remain elusive. Recent work investigating the ability of Vif from different lentiviruses for cross-species transcomplementation suggests that Vif itself functions in a host cell-dependent manner, supporting the notion that Vif may interact with as yet unknown cellular factors (57).

Why is VIF not able to interact with nucleocapsid?

The inability of Vif to associate with the nucleocapsid mutant viruses could be a consequence of the reduced ability of these viruses to package viral genomic RNA or result from the inability of Vif to interact with the mutant nucleocapsid protein itself. To address this question, we analyzed the efficiency of Vif incorporation into an HIV-1 RNA-packaging mutant, C-Help (42). Unlike the NC zinc finger mutants, C-Help does not carry mutations in the viral gaggene but lacks a putative RNA-packaging motif upstream of the Gag coding region and, in addition, lacks both viral LTRs (Fig. ?(Fig.5A).5A). Thus, the lack of packaging of viral genomic RNA is due to a defect in the viral RNA rather than the viral capsid. Analysis of C-Help virus preparations by endogenous RT assay did not reveal detectable levels of viral RNAs (see Fig. ?Fig.7).7). HeLa cells were transiently transfected with C-Help plasmid DNA as described above. Virus-containing supernatants were harvested 48 h after transfection and concentrated by ultracentrifugation. Concentrated virus preparations were either analyzed directly (Fig. ?(Fig.5,5, lane b) or subjected to sucrose step gradient centrifugation (lanes c to e). Three equal fractions were collected from the step gradient, as indicated in the diagram in Fig. ?Fig.5.5. Whole-cell lysates (lane a) and viral fractions were subjected to immunoblot analysis using an HIV-positive patient serum or a Vif-specific antiserum. Only small amounts of Vif were detectable in concentrated virus preparations (lane b), which were below the level of detection following step gradient centrifugation. Quantitation of the Vif-specific bands from cell lysates and concentrated virus preparations (lanes a and b) was done, as shown in Fig. ?Fig.4C.4C. The amount of Vif identified in the concentrated virus preparation (lane b) corresponded to approximately 3.5% of total Vif, which is comparable to the level of nonspecific Vif secretion observed in HeLa cells in the absence of virus production or in cells producing the NC zinc finger mutant (Fig. ?(Fig.4C,4C, pNL-A1 and pDB653). The level of Vif found in C-Help virus preparations is well below the levels found in wild-type NL4-3 preparations, which were consistently in excess of 10% of total Vif. Thus, deletion of the viral LTRs and a putative RNA-packaging signal of the viral genomic RNA severely restricted Vif incorporation into virions. These results suggest that packaging of Vif into virus particles occurs concomitant with the packaging of viral genomic RNA. These results also suggest that the impact of NC zinc finger mutations of Vif packaging is not the result of a loss of interaction between Vif and NC but a consequence of the reduced RNA packaging exhibited by those mutants.

What is the VIF protein?

Vif is a basic, 23-kDa protein that is expressed from a singly spliced mRNA in HIV-infected cells. Immunocytochemical analyses reveal a largely cytoplasmic localization of Vif (24, 34, 53). Two recent reports suggest that Vif associates with viral genomic RNA in vivo and in vitro (15, 72), and deletions in the N-terminal and central regions of Vif were found to affect its ability to bind to poly(G)-conjugated agarose beads in vitro (72). Aside from its affinity to RNA, Vif was reported to associate with cellular membranes through a mechanism involving a basic C-terminal domain in Vif (24, 26, 60). This same domain was also reported to be responsible for the interaction of Vif with the Gag precursor Pr55gag(8), and mutations in the basic domain were found to abolish biological activity of Vif (8, 26). In addition to the C-terminal basic domain, Vif proteins contain two conserved cysteine residues which are important for its biological activity (10, 40). The precise function of these cysteine residues in unclear; however, they do not appear to be involved in the formation of intramolecular disulfide bridges and are more likely to constitute part of a functional domain in Vif (60). Finally, a significant amount of Vif can be found in association with the intermediate filament network in virus-producing cells (34); however, the domain(s) in Vif responsible for this association remains unclear.

What is pNL4-3 used for?

The full-length molecular clone pNL4-3 (1) was used for the production of wild-type infectious virus. An Env-defective variant, pNLenv-1, was constructed by deleting a KpnI-BglII fragment from the pNL4-3 envgene (nucleotides 6343 to 7611 in the pNL4-3 sequence). Two RNA packaging-defective nucleocapsid mutants of NL4-3, pRB73-B, carrying histidine-to-cysteine mutations in the nucleocapsid zinc finger domains (H23C and H44C), and pDB653, carrying cysteine-to-serine mutations (C15S, C18S, C28S, C36S, C39S, and C49S), have been described elsewhere (27, 30). Based on Northern blot analysis, the full-length genomic RNA content of DB653 virions is <10% that of wild-type virus (30). Similarly, the full-length genomic RNA content of RB73-B virions was reduced to approximately 5% that of wild-type virus (27). Another RNA packaging-defective virus, C-Help, was obtained from Hideki Mochizuki (42). C-Help is defective for packaging of viral genomic RNA due to a deletion of a putative RNA packaging signal. In addition, C-Help lacks the two viral long terminal repeats (LTRs) and carries a deletion in the envgene. Plasmid pHCMV-G contains the vesicular stomatitis, virus (VSV) glycoprotein G (VSV-G) gene expressed from the immediate-early gene promoter of human cytomegalovirus (69) and was used for the production of VSV-G pseudotypes. For transient expression of Vif, the subgenomic expression vector pNL-A1 (62) was employed. This plasmid expresses all HIV-1 proteins except for gagand polproducts. A Vif-defective variant of pNL-A1, pNL-A1Δvif, was constructed by deletion of an NdeI-PflMI fragment in vif, resulting in a translational frameshift following amino acid 28 (34). The Vif deletion mutant VifΔG (deletion of amino acids 75 to 114) was created by two-step PCR amplification. The initial set of PCR fragments was produced using primers A5 (TTAGACCAGA TCTGAGCCTG GGAGC), A3 (TAGCAGAGTC TGAAAATGTA TGCAGACCCC), and B5 (TGGGGTCTGC ATACATTTTC AGACTCTGC) and B3 (AAACAGCAGT TGTTGCAGAA TTC). The resulting PCR products A and B were column purified, mixed at equimolar ratios, and used as templates for a second round of amplification using the flanking primers A5 and B3. The final PCR product was purified, digested with BssHII and EcoRI, and cloned into the BssHII and EcoRI sites of pNL-A1. The in-frame deletion mutants VifΔB (deletion of residues 157 to 184), VifΔC (deletion of residues 144 to 149), and VifΔD (deletion of residues 23 to 43) were constructed using similar two-step PCR approaches. The presence of the desired deletions and the absence of additional PCR-induced mutations were verified by sequence analysis.