Live-cell 3D-SIM of Rift Valley fever virus NSs filaments reveals a polygon web architecture

Journal article

A defining feature of Rift Valley fever virus (RVFV) is the incorporation of the NSs protein into large filamentous assemblies inside infected nuclei [R. Swanepoel, N. K. Blackburn, J. Gen. Virol. 34, 557–561 (1977).], as judged from fixed specimens. To gain insight into the 3D structure of NSs filaments within live-cell nuclei, we used genetic-code expansion (GCE) to incorporate trans-cyclooct-2-en-L-lysine into the protein. This enabled site-specific fluorescent labeling with tetrazine dyes for live-cell structured illumination microscopy (SIM). Our superresolved images revealed the complete native architecture of NSs filaments as a micron-scale polygon web of fibers with discrete domain characteristics, overturning previous assumptions of simple linear filaments. Parallel experiments on fixed RVFV-infected cells confirmed that native NSs filaments also display this morphology. Overall, our 3D-SIM analysis reveals distinct structural plasticity within NSs filaments, establishing a quantitative structure–function relationship that support the importance of polygon organization for NSs filament function during RVFV infection.

Authors: Dunlop, JI; Thomason, PA; Carlin, LM; Davis, BG; Carter, SD

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: National Academy of Sciences
• Journal: Proceedings of the National Academy of Sciences
• Volume: 123
• Issue: 12
• Article number: e2534404123
• Publication date: 2026-03-16
• Acceptance date: 2026-02-10
• DOI: 10.1073/pnas.2534404123
• EISSN: 1091-6490
• ISSN: 0027-8424
• Language: English
• Keywords: nucleus; in situ structural biology; super-resolution microscopy