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HIV-1 sequences isolated from patients promote expression of shorter isoforms of the Gag polyprotein

Christelle Daudé1,2,3,4,5,6, Didier Décimo1,2,3,4,5, Mary-Anne Trabaud7

  • 1CIRI, International Center for Infectiology Research, Université de Lyon, 46 Allée d'Italie, 69364, Lyon, France.

Archives of Virology
|September 24, 2016
PubMed

Insights

Human immunodeficiency virus type 1 (HIV-1) unspliced mRNA translation initiation varies among clinical isolates. Clinical HIV-1 sequences drive Gag polyprotein expression via AUG-p55 and AUG-p40 codons, impacting viral replication.

Area of Science:

  • Molecular Biology
  • Virology
  • Genetics

Background:

  • Human immunodeficiency virus type 1 (HIV-1) unspliced mRNA utilizes both cap-dependent and internal ribosome entry site (IRES)-dependent mechanisms for Gag and Gag-Pol polyprotein expression.
  • A previously described IRES in the matrix coding region facilitates shorter Gag isoform production, but this was only demonstrated with laboratory strains (NL4.3, HXB2), not clinical isolates.

Purpose of the Study:

  • To investigate the translational activity of internal ribosome entry site (IRES) sequences from clinical HIV-1 isolates.
  • To analyze the ability of these sequences to drive the expression of Gag p55 and shorter Gag isoforms in vitro and ex vivo.
  • To determine the impact of the initial ~800 nucleotides of HIV-1 unspliced mRNA on translation initiation at AUG-p55 and AUG-p40 codons.

Main Methods:

  • Isolation and sequencing of approximately 70 HIV-1 sequences from infected patients.
  • Cloning of these sequences into an expression vector.
  • In vitro and ex vivo monitoring of translation initiation at AUG-p55 and AUG-p40 codons using reporter assays, particularly in Jurkat T cells.

Main Results:

  • Significant variation in translational efficiency from the AUG-p55 codon was observed among different clinical HIV-1 isolates.
  • Expression initiated at the AUG-p40 codon was independent of translation initiation at the AUG-p55 codon.
  • All tested sequences promoted the expression of shorter Gag isoforms, with exclusive internal initiation at the AUG-p40 codon observed in Jurkat T cells.

Conclusions:

  • The composition of the first ~800 nucleotides of HIV-1 unspliced mRNA modulates translation initiation at both AUG-p55 and AUG-p40 codons, potentially influencing viral production and replication.
  • The AUG-p40 codon and its surrounding nucleotide context are conserved in clinical isolates and function as a translation initiation site for producing shorter Gag isoforms.

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