A minimal uORF within the HIV-1 vpu leader allows efficient translation initiation at the downstream env AUG

• Published in: Virology (New York, N.Y.) Vol. 363; no. 2; pp. 261 - 271
• Main Authors: Krummheuer, Jörg, Johnson, Adam T, Hauber, Ilona, Kammler, Susanne, Anderson, Jenny L, Hauber, Joachim, Purcell, Damian F.J, Schaal, Heiner
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 05.07.2007
• Subjects: Base Sequence; Downstream translation; Gene Expression; HeLa Cells; HIV; HIV-1 - physiology; Human immunodeficiency virus 1; Humans; Infectious Disease; Molecular Sequence Data; Non-linear scanning; Open Reading Frames - physiology; Polycistronic mRNA; Protein Biosynthesis; RNA, Messenger - genetics; Sequence Alignment; uORF; Up-Regulation; Viral Envelope Proteins - genetics; uORF; Downstream translation; Polycistronic mRNA; HIV; Non-linear scanning
• ISSN: 0042-6822; 1096-0341
• DOI: 10.1016/j.virol.2007.01.022

Abstract The HIV-1 Vpu and Env proteins are translated from 16 alternatively spliced bicistronic mRNA isoforms. Translation of HIV-1 mRNAs generally follows the ribosome scanning mechanism. However, by using subgenomic env expression vectors, we found that translation of glycoprotein from polycistronic mRNAs was inconsistent with leaky scanning. Instead a conserved minimal upstream open reading frame (uORF) consisting only of a start and stop codon that overlaps with the vpu start site, appears to augment access to the env start codon downstream. Mutating the translational start and stop codons of this uORF resulted in up to fivefold reduction in Env expression. Removing the vpu uORF and increasing the strength of the authentic vpu initiation sequence abolished Env expression from subgenomic constructs and replication of HIV-1, whereas an identical increase in the strength of the minimal uORF initiation site did not alter Env expression.