Identification of host dependency factors involved in SARS-CoV-2 replication organelle formation through proteomics and ultrastructural analysis.

Positive-strand RNA viruses subvert the cellular endomembrane system for the generation of distinct compartments termed replication organelles (ROs) that harbor the site where viral RNAs are generated. In this study, we corroborate that the SARS-CoV-2 non-structural proteins 3 and 4 (nsp3 and nsp4) suffice to remodel the endoplasmic reticulum to form double-membrane vesicles similar to ROs observed in viral infection. Cellular membrane alterations induced by nsp3/4 expression were evaluated through electron tomography and confocal microscopy, and nsp3/4-associated host factors were identified using mass spectrometry. The role of these host factors in virus infection was determined using gene silencing, identifying several host proteins involved in the SARS-CoV-2 replication cycle. Combining the gene silencing approach with ultrastructural analysis of nsp3/4-expressing cells, we found that the host dependency factors FAM149B1, CCAR2, and ZC3HAV1 play a role in the formation of double-membrane vesicles in a replication-independent manner. [ABSTRACT FROM AUTHOR]