Molten globule driven and self-downmodulated phase separation of a viral factory scaffold

de Prat Gay, G.; Salgueiro, M.; Camporeale, G.; Visentin, A.; Aran, M.; Pellizza, L.; Esperante, S. A.; Corbat, A.; Grecco, H.; Sousa, B.; Esperon, R.; Borkosky, S.

doi:10.1101/2023.01.27.525862

bioRxiv · 10.1101/2023.01.27.525862

Molten globule driven and self-downmodulated phase separation of a viral factory scaffold

de Prat Gay, G.·Salgueiro, M.·Camporeale, G.·Visentin, A.·Aran, M.·Pellizza, L.·Esperante, S. A.·Corbat, A.·Grecco, H.·Sousa, B.·Esperon, R.·Borkosky, S.

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Abstract

Viral factories of liquid-like nature host transcription and replication in most viruses. The syncytial respiratory virus factories include gene function proteins, brought together by the phosphoprotein (P) RNA polymerase cofactor, present across non-segmented negative stranded RNA viruses. Homotypic liquid-liquid phase separation of RSV-P is governed by an -helical molten globule domain, and strongly self-downmodulated by adjacent sequences. Condensation of P with the nucleoprotein N is stoichiometrically tuned, defining aggregate-droplet and droplet-dissolution boundaries. Time course analysis show small N-P nuclei gradually coalescing into large granules in transfected cells. This behavior is recapitulated in infection, with small puncta evolving to large viral factories, strongly suggesting that P-N nucleation-condensation sequentially drives viral factories. Thus, the tendency of P to undergo phase separation is moderate and latent in the full-length protein but unleashed in the presence of N or when neighboring disordered sequences are deleted. This, together with its capacity to rescue nucleoprotein-RNA aggregates suggests a role as a "solvent-protein" and possible fluidity tuner of viral factories.

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de Prat Gay, G., Salgueiro, M., Camporeale, G., Visentin, A., Aran, M., Pellizza, L., Esperante, S. A., Corbat, A., Grecco, H., Sousa, B., Esperon, R., Borkosky, S.. 2023-01-27. Molten globule driven and self-downmodulated phase separation of a viral factory scaffold. https://doi.org/10.1101/2023.01.27.525862

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