Durieux Trouilleton, Q. | Search bioRxiv

bioRxiv2026

Hantaan virus polymerase has an in vitro Terminal Nucleotidyl Transferase activity that is conserved across the Bunyaviricetes class

Bunyaviricetes is a class of segmented negative strand RNA viruses (sNSV) that includes causative agents of severe zoonotic diseases resulting in hemorrhagic fever in humans and livestock. Hantaan virus (HTNV), family Hantaviridae, is an example of life-threatening bunyavirus transmitted by rodents which leads to Hantavirus hemorrhagic fever with renal syndrome in humans. Infection relies on the replication and transcription of their tripartite genomes through multifunctional RNA-dependent RNA polymerases (RdRp) in the context of ribonucleoproteins (RNPs) made of one viral RNA fragment, one RdRp and multiple copies of viral nucleoproteins. The RdRp, also known as L protein, performs replication by de novo initiation through a prime-and-realign mechanism while transcription initiates through a cap snatching mechanism, that engages a cap-binding domain and an endonuclease (EN) domain present in the L protein C and N terminal regions, respectively. In this work we show that HTNV L protein has a terminal nucleotidyl transferase (TNTase) activity over double-stranded RNA substrates (dsRNA) in vitro. We show that the TNTase activity is also present in other bunyaviral L proteins by comparing HTNV L protein activity with La Crosse (LACV, family Orthobunyaviridae) and Crimean Congo Hemorrhagic Fever Virus (CCHFV, family Nairoviridae) L proteins. Our results show that TNTase activity appears to be a general feature of Bunyaviruses and report the differences on substrate and nucleotide specificity for each family of virus.

biochemistry↗

bioRxiv2023

Structural characterization of the oligomerization of full-length Hantaan virus polymerase into symmetric dimers and hexamers

Hantaan virus is a dangerous human pathogen whose segmented negative-stranded RNA genome is replicated and transcribed by a virally-encoded multi-functional polymerase. Here we describe the complete cryo-electron microscopy structure of Hantaan virus polymerase in several oligomeric forms. Apo polymerase protomers can adopt two drastically different conformations, which assemble into two distinct homodimers, that can themselves gather to form hexamers. Polymerase dimerization induces the stabilization of most polymerase domains, including the C-terminal region that notably contains a C-terminal domain that contribute the most to dimers interface, along with a lariat region that participates to the polymerase steadying. Binding to viral RNA induces significant conformational changes resulting in oligomer disruption, suggesting the possible involvement of multimers as protecting systems that would stabilize the otherwise flexible C-terminal domains. Overall, these results provide new insights into the multimerization capability of Hantavirus polymerase and may help to define antiviral compounds to counteract these life-threatening viruses.

biochemistry↗