Severe Acute Respiratory Syndrome Coronavirus Nonstructural Proteins 3, 4, and 6 Induce Double-Membrane Vesicles

Angelini, Megan M.; Akhlaghpour, Marzieh; Neuman, Benjamin W.; Buchmeier, Michael J.

Similar to other positive-sense, single-stranded RNA viruses, coronavirus genomic replication and transcription are moderated by a large RNA replication complex that is anchored in rearranged internal host membranes (22) (23) (24) (25) (26) (27) (28) (29) . These membranes act as a framework for viral genome replication by localizing and concentrating the necessary factors and possibly providing protection from host cell defenses. The hallmark membrane rearrangements observed upon coronavirus infection are double-membrane vesicles (DMVs), named for their distinctive double-lipid bilayer as seen in electron micrographs. These DMVs are found in conjunction with reticular regions of a convoluted membrane (CM) between them, and contiguity with the endoplasmic reticulum (ER) has been observed in electron microscopy (EM) despite a lack of canonical ER membrane markers (30) (31) (32) (33) (34) (35) . Certain subsets of the coronavirus replication machinery have been shown to move in the cell in a manner that corresponds with microtubule-associated transport, but microtubule disruption does not have an effect on viral genome replication levels (32) . Although much has been done to study coronavirus-induced DMVs, it remains unclear which specific viral proteins are responsible for their induction and which host cellular membranes or processes are engaged (29, (36) (37) (38) (39) .