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bioRxiv · 10.1101/2022.05.23.493138

Reconstitution of the SARS-CoV-2 ribonucleosome provides insights into genomic RNA packaging and regulation by phosphorylation

Carlson, C.·Adly, A.·Bi, M.·Cheng, Y.·Morgan, D. O.
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Abstract

The nucleocapsid (N) protein of coronaviruses is responsible for compaction of the [~]30-kb RNA genome in the [~]100-nm virion. Cryo-electron tomography suggests that each virion contains 35-40 viral ribonucleoprotein (vRNP) complexes, or ribonucleosomes, arrayed along the genome. There is, however, little mechanistic understanding of the vRNP complex. Here, we show that N protein, when combined with viral RNA fragments in vitro, forms cylindrical 15-nm particles similar to the vRNP structures observed within coronavirus virions. These vRNPs form in the presence of stem-loop-containing RNA and depend on regions of N protein that promote protein-RNA and protein-protein interactions. Phosphorylation of N protein in its disordered serine/arginine (SR) region weakens these interactions and disrupts vRNP assembly. We propose that unmodified N binds stem-loop-rich regions in genomic RNA to form compact vRNP complexes within the nucleocapsid, while phosphorylated N maintains uncompacted viral RNA to promote the proteins transcriptional function.

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Carlson, C., Adly, A., Bi, M., Cheng, Y., Morgan, D. O.. 2022-05-24. Reconstitution of the SARS-CoV-2 ribonucleosome provides insights into genomic RNA packaging and regulation by phosphorylation. https://doi.org/10.1101/2022.05.23.493138

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