Characterization of SARS-CoV-2 nucleocapsid protein oligomers

Farci, Domenica

First

;Graça, André T;Hall, Michael;Haniewicz, Patrycja;Kereïche, Sami;Faull, Peter;Kirkpatrick, Joanna;Tramontano, Enzo;Schröder, Wolfgang P;Piano, Dario

Last

2025-01-01

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Abstract

Oligomers of the SARS-CoV-2 nucleocapsid (N) protein are characterized by pronounced instability resulting in fast degradation. This property likely relates to two contrasting behaviors of the N protein: genome stabilization through a compact nucleocapsid during cell evasion and genome release by nucleocapsid disassembling during infection. In vivo, the N protein forms rounded complexes of high molecular mass from its interaction with the viral genome. To study the N protein and understand its instability, we analyzed degradation profiles under different conditions by size-exclusion chromatography and characterized samples by mass spectrometry and cryo-electron microscopy. We identified self-cleavage properties of the N protein based on specific Proprotein convertases activities, with Cl- playing a key role in modulating stability and degradation. These findings allowed isolation of a stable oligomeric complex of N, for which we report the 3D structure at ∼6.8 Å resolution. Findings are discussed considering available knowledge about the coronaviruses’ infection cycle.