Functional comparison of the two gene products of Thogoto virus segment 6

This study examined the functional differences between the two proteins encoded by segment 6 of Thogoto virus (THOV), the matrix protein (M) and the accessory protein ML. Although these proteins share nearly identical sequences, the authors aimed to determine whether they perform similar or distinct roles during infection. Using minireplicon assays, mutational analysis, and reporter-based experiments, the study showed that M is essential for viral replication and assembly. M strongly inhibited the viral RNA-dependent RNA polymerase (RdRP), thereby suppressing viral transcription. This inhibitory activity was localized to the C-terminal region, while the full-length protein was required for the formation of virus-like particles (VLPs). In contrast, ML did not affect polymerase activity and could not support particle formation. Instead, ML functioned as an interferon (IFN) antagonist, efficiently blocking IFN-β induction in response to viral infection or double-stranded RNA. This activity was associated with the C-terminal region of ML but required more than just the unique 38-amino-acid extension. Additionally, ML was found to be incorporated into virions, suggesting a role early in infection. Overall, the study demonstrates that M and ML have clearly distinct functions, with M involved in replication and assembly, and ML specialized in immune evasion.
(TMR)