Genomic RNA Elements Drive Phase Separation of the SARS-CoV-2 Nucleocapsid
M.A. Boerneke, Carola Weidmann, Timothy P. Sheahan, Yixuan J. Hou, J. Ekena, Ralph S. Baric, O.G. Troyanskaya, I. Jungreis, A.S. Gladfelter, R.S.G. Sealfon, M. Kellis, C.A. Roden, K.M. Weeks, C. Iserman, C.L. Theesfeld, E.J. Fritch, Guest Mclaughlin
Abstract
We report that the SARS-CoV-2 nucleocapsid protein (N-protein) undergoes liquid-liquid phase separation (LLPS) with viral RNA. N-protein condenses with specific RNA genomic elements under physiological buffer conditions and condensation is enhanced at human body temperatures (33°C and 37°C) and reduced at room temperature (22°C). RNA sequence and structure in specific genomic regions regulate N-protein condensation while other genomic regions promote condensate dissolution, potentially preventing aggregation of the large genome. At low concentrations, N-protein preferentially crosslinks to specific regions characterized by single-stranded RNA flanked by structured elements and these features specify the location, number, and strength of N-protein binding sites (valency). Liquid-like N-protein condensates form in mammalian cells in a concentration-dependent manner and can be altered by small molecules. Condensation of N-protein is RNA sequence and structure specific, sensitive to human body temperature, and manipulatable with small molecules, and therefore presents a screenable process for identifying antiviral compounds effective against SARS-CoV-2.