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

Das, Atze T.; Klaver, Bep; Berkhout, Ben

doi:10.1128/jvi.72.11.9217-9223.1998

Cited by 52 publications

(23 citation statements)

References 62 publications

(81 reference statements)

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“…That study did not define the actual role played by the lower portion of the stem, although it did suggest that the lower stem structure might be necessary for transcription, RNA packaging, or reverse transcription. Other genetic studies have also suggested functions of TAR that go beyond its role in transactivation (15,(29)(30)(31). Furthermore, a recent report demonstrated decreased (about 3.5-fold) packaging in an HIV vector mutant containing a total deletion of TAR (48).…”

Section: Discussionmentioning

confidence: 97%

An Intact TAR Element and Cytoplasmic Localization Are Necessary for Efficient Packaging of Human Immunodeficiency Virus Type 1 Genomic RNA

Helga-Maria

Hammarskjöld

Rekosh

1999

J Virol

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Although most reports defining the human immunodeficiency virus type 1 (HIV-1) genomic RNA packaging signal have focused on the region downstream of the major 5′ splice site, others have suggested that sequences upstream of the splice site may also play an important role. In this study we have directly examined the role played by the HIV-1 TAR region in RNA packaging. For these experiments we used a proviral expression system that is largely independent of Tat for transcriptional activation. This allowed us to create constructs that efficiently expressed RNAs carrying mutations in TAR and to determine the ability of these RNAs to be packaged. Our results indicate that loss of sequences in TAR significantly reduce the ability of a viral RNA to be packaged. The requirement for TAR sequences in RNA packaging was further examined by using a series of missense mutations positioned throughout the entire TAR structure. TAR mutations previously shown to influence Tat transactivation, such as G31U in the upper loop region or UCU to AAG in the bulge (nucleotides [nt] 22 to 24), failed to have any effect on RNA packaging. Mutations which disrupted the portion of the TAR stem immediately below the bulge also had little effect. In contrast, dramatic effects on RNA packaging were observed with constructs containing mutations in the lower portion of the TAR stem. Point mutations which altered nt 5 to 9, 10 to 15, 44 to 49, or 50 to 54 all reduced RNA packaging 11- to 25-fold. However, compensatory double mutations which restored the stem structure were able to restore packaging. These results indicate that an intact lower stem structure, rather than a specific sequence, is required for RNA packaging. Our results also showed that RNA molecules retained within the nucleus cannot be packaged, unless they are transported to the cytoplasm by either Rev/Rev response element or the Mason-Pfizer monkey virus constitutive transport element.

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Section: Discussionmentioning

confidence: 97%

An Intact TAR Element and Cytoplasmic Localization Are Necessary for Efficient Packaging of Human Immunodeficiency Virus Type 1 Genomic RNA

Helga-Maria

Hammarskjöld

Rekosh

1999

J Virol

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“…Transcription of proviral DNA generates genomic full length retroviral mRNA that functions as genomic and messenger RNA, and possesses well-defined functional domains, including the R region, which corresponds to the +1 site of transcription and the site of capping, the 5′-untranslated region (5′-UTR) or leader, the viral ORFs, the 3′-UTR and the 3′-poly (A) tail. The 5′-UTR of the genomic RNA contains cis-acting RNA structures that are crucially involved in various aspects of the viral life cycle [14][15][16][17][18] (FIG. 2).…”

Section: ′-Cap Structurementioning

confidence: 99%

Translational control of retroviruses

Balvay¹,

López‐Lastra²,

Sargueil³

et al. 2007

Nat Rev Microbiol

115

124

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All replication-competent retroviruses contain three main reading frames, gag, pol and env, which are used for the synthesis of structural proteins, enzymes and envelope proteins respectively. Complex retroviruses, such as lentiviruses, also code for regulatory and accessory proteins that have essential roles in viral replication. The concerted expression of these genes ensures the efficient polypeptide production required for the assembly and release of new infectious progeny virions. Retroviral protein synthesis takes place in the cytoplasm and depends exclusively on the translational machinery of the host infected cell. Therefore, not surprisingly, retroviruses have developed RNA structures and strategies to promote robust and efficient expression of viral proteins in a competitive cellular environment.

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“…Binding of Tat to TAR leads to transcriptional activation of the lentiviral promoter located in the U3 region of the 59 LTR of the proviral DNA (reviewed by Cullen, 1992;Daelemans et al, 2000). In addition, the R region of Human immunodeficiency virus 1 (HIV-1) has been reported to enhance packaging efficiency (Das et al, 1997(Das et al, , 1998McBride et al, 1997;Clever et al, 1999;Helga-Maria et al, 1999). The multiple functions of R at different steps of the virus life cycle render modifications of the R region of retroviral vectors difficult.…”

Section: Introductionmentioning

confidence: 99%

Functional replacement of the R region of simian immunodeficiency virus-based vectors by heterologous elements

Brandt

Grünwald

Lucke

et al. 2006

Journal of General Virology

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Substitution of lentiviral cis-acting elements by heterologous sequences might allow the safety of lentiviral vectors to be enhanced by reducing the risk of homologous recombination and vector mobilization. Therefore, a substitution and deletion analysis of the R region of simian immunodeficiency virus (SIV)-based vectors was performed and the effect of the modifications on packaging and transfer by SIV and human immunodeficiency virus type 1 (HIV-1) particles was analysed. Deletion of the first 7 nt of R reduced vector titres by 10-to 20-fold, whilst deletion of the entire R region led to vector titres that were 1500-fold lower. Replacement of the R region of SIV-based vectors by HIV-1 or Moloney murine sarcoma virus R regions partially restored vector titres. A non-retroviral cellular sequence was also functional, although to a lesser extent. In the absence of tat, modification of the R region had only minor effects on cytoplasmic RNA stability, steady-state levels of vector RNA and packaging, consistent with the known primary function of R during reverse transcription. Although the SIV R region of SIV-based vectors could be replaced functionally by heterologous sequences, the same modifications of R led to a severe replication defect in the context of a replication-competent SIV. As SIV-based vectors containing the HIV-1 R region were transferred less efficiently by HIV-1 particles than wild-type SIV vectors, a match between R and cis-acting elements of the vector construct seems to be more important than a match between R and the Gag or Pol proteins of the vector particle.

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

Cited by 52 publications

References 62 publications

An Intact TAR Element and Cytoplasmic Localization Are Necessary for Efficient Packaging of Human Immunodeficiency Virus Type 1 Genomic RNA

An Intact TAR Element and Cytoplasmic Localization Are Necessary for Efficient Packaging of Human Immunodeficiency Virus Type 1 Genomic RNA

Translational control of retroviruses

Functional replacement of the R region of simian immunodeficiency virus-based vectors by heterologous elements

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