PT  - JOURNAL ARTICLE
AU  - Carlson, Christopher R.
AU  - Adly, Armin N.
AU  - Bi, Maxine
AU  - Cheng, Yifan
AU  - Morgan, David O.
TI  - Reconstitution of the SARS-CoV-2 ribonucleosome provides insights into genomic RNA packaging and regulation by phosphorylation
AID  - 10.1101/2022.05.23.493138
DP  - 2022 Jan 01
TA  - bioRxiv
PG  - 2022.05.23.493138
4099  - http://biorxiv.org/content/early/2022/05/24/2022.05.23.493138.short
4100  - http://biorxiv.org/content/early/2022/05/24/2022.05.23.493138.full
AB  - 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 protein’s transcriptional function.Competing Interest StatementThe authors have declared no competing interest.