Regulation of Tacaribe Mammarenavirus Translation: Positive 5’ and Negative 3’ Elements, and Role of Key Cellular Factors.

FOSCALDI, SABRINA; D'ANTUONO, ALEJANDRA; NOVAL, MARÍA GABRIELA; DE PRAT GAY, GONZALO; SCOLARO, LUIS; LOPEZ, NORA

JOURNAL OF VIROLOGY

AMER SOC MICROBIOLOGY

Lugar: Washington; Año: 2017

0022-538X

Mammarenaviruses are enveloped viruses with a bisegmented negative-stranded RNA genome that encodes the nucleocapsid protein (NP), the envelope glycoprotein precursor (GPC), the RNA polymerase (L), and a RING matrix protein (Z). Viral proteins are synthesized from subgenomic messenger RNAs bearing a capped 5´ untranslated region (UTR), and lacking 3´ poly(A) tail. We analyzed the translation strategy of Tacaribe virus (TCRV), a prototype of the New World mammarenaviruses. A virus-like transcript that carries a reporter gene in place of the NP open-reading frame as well as transcripts bearing modified 5´ and/or 3´ UTRs were evaluated in a cell-based translation assay. We found that the presence of the cap structure at the 5´ end dramatically increases translation efficiency, and that the viral 5´ UTR comprises stimulatory signals while the 3´ UTR, and specifically the presence of a terminal C+G-rich sequence and/or a stem-loop structure, down-modulates translation. Additionally, translation was profoundly reduced in eukaryotic initiation factor (eIF) 4G-inactivated cells, whereas depletion of intracellular levels of eIF4E had lesser impact on virus-like mRNA translation, as compared with a cell-like transcript. Translation efficiency was independent of NP expression or TCRV infection. Our results indicate that TCRV mRNAs are translated using a cap-dependent mechanism, whose efficiency relies on the interplay between stimulatory signals in the 5´ UTR and a negative modulatory element in the 3´ UTR. The low dependence on eIF4E suggests that viral mRNAs may engage yet unknown non-canonical host factors for a cap-dependent initiation mechanism.IMPORTANCE Several members of the Arenaviridae family cause serious hemorrhagic fevers in humans. In the present report, we describe the mechanism by which Tacaribe virus, a prototypic non-pathogenic NW mammarenavirus, regulates viral mRNA translation. Our results highlight the impact of untranslated sequences and key host translation factors on this process. We propose a model that explains how viral mRNAs outcompete cellular mRNAs for the translation machinery. A better understanding of the mechanism of translation regulation of this virus can provide the bases for the rational design of new antiviral tools directed to pathogenic arenaviruses.