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. 2020 Mar 30;30(4):343–355. doi: 10.1038/s41422-020-0305-x

Fig. 1. Establishment of SARS-CoV-2 S protein-mediated cell–cell fusion system.

Fig. 1

a The emerging timeline for highly pathogenic viruses and the proposed Disease X. b Schematic representation of SARS-CoV-2 S protein. Its S1 subunit contains NTD (14–305 aa), RBD (319–541 aa), and RBM (437–508 aa). Its S2 subunit contains FP (788–806 aa), HR1 (912–984 aa), HR2 (1163–1213 aa), TM (1214–1237 aa) and CP (1238–1273 aa). c The formation of syncytium in Huh-7 cells 24 h after SARS-CoV-2 infection, with scale bar of 200 µm. d Images of SARS-CoV and SARS-CoV-2 S-mediated cell–cell fusion on 293T/ACE2 cells at 2 h (left) and 24 h (right). e SARS-CoV (I–II) and SARS-CoV-2 (III–IV) S-mediated syncytium formation on 293T/ACE2 cells at 48 h. f SARS-CoV (I–II) and SARS-CoV-2 (III–IV) S-mediated syncytium formation on Huh-7 cells at 48 h. Scale bar equals 400 µm in d–f.