In Situ Hybridization-Proximity Ligation Assay (ISH-PLA) to Study the Interaction of HIV-1 RNA and Remodeling Proteins

The viral nucleocapsid protein and the human RNA-binding protein Mex3A promote translation of the Andes orthohantavirus small mRNA

The capped Small segment mRNA (SmRNA) of the Andes orthohantavirus (ANDV) lacks a poly(A) tail. In this study, we characterize the mechanism driving ANDV-SmRNA translation. Results show that the ANDV-nucleocapsid protein (ANDV-N) promotes in vitro translation from capped mRNAs without replacing eukaryotic initiation factor (eIF) 4G. Using an RNA affinity chromatography approach followed by mass spectrometry, we identify the human RNA chaperone Mex3A (hMex3A) as a SmRNA-3’UTR binding protein. Results show that hMex3A enhances SmRNA translation in a 3’UTR dependent manner, either alone or when co-expressed with the ANDV-N. The ANDV-N and hMex3A proteins do not interact in cells, but both proteins interact with eIF4G. The hMex3A–eIF4G interaction showed to be independent of ANDV-infection or ANDV-N expression. Together, our observations suggest that translation of the ANDV SmRNA is enhanced by a 5’-3’ end interaction, mediated by both viral and cellular proteins.

Andes orthohantavirus (ANDV) is endemic in Argentina and Chile and is the primary etiological agent of hantavirus cardiopulmonary syndrome (HCPS) in South America. ANDV is unique among other members of the Hantaviridae family of viruses because of its ability to spread from person to person. The molecular mechanisms driving ANDV protein synthesis remain poorly understood. A previous report showed that translation of the Small segment mRNA (SmRNA) of ANDV relied on both the 5’cap and the 3’untranslated region (UTR) of the SmRNA. In this new study, we further characterize the mechanism by which the 5’ and 3’end of the SmRNA interact to assure viral protein synthesis. We establish that the viral nucleocapsid protein N and the cellular protein hMex3A participate in the process. These observations indicated that both viral and cellular proteins regulate viral gene expression during ANDV infection by enabling the viral mRNA to establish a non-covalent 5’-3’end interaction.