Inhibition of Hsp90 activity posttranslationally decreases the amount of SARS-CoV2 proteins. Effect of overexpression (A) or knockout (B) of two Hsp90 isoforms on SARS-CoV-2 Orf7a, Orf7b, Orf3, M, and N protein expression. C and D, effect of overexpression of Hsp90β (C) or Hsp90α (D) on SARS-CoV-2 Orf7a, Orf7b, Orf3, M, and N protein expression in 90β-KO HEK293T cells. E, WT, 90α-KO, or 90β-KO HEK293T cells were transfected with M-mCherry or N-GFP vectors for 24 h and observed by fluorescence microscopy. F, cytotoxicity was measured in HEK293T cells after 12 h treatment with 17-DMAG. Cell viability was determined and calculated as a percentage of the viable cells after treatment with DMSO. G, HEK293T cells were transfected with pRK5-N or pRK5-M, and at 12 h post-transfection (hpt), fresh medium was added containing the indicated concentrations of 17-DMAG. At 24 hpt, cell lysates were subjected to immunoblot with the indicated antibodies. β-actin was used to normalize band intensity and the relative expression level of each viral protein was based on the levels of vehicle (0 μM 17-DMAG)-treated cells. H, HEK293T cells were transfected with pRK5-N or pRK5-M and fresh medium containing 10 μM 17-DMAG was added at the indicated times. At 24 hpt, cell lysates were subjected to immunoblot with the indicated antibodies. β-actin was used to normalize band intensity and the relative expression level of each viral protein was based on the levels of DMSO-treated cells; ∗p ≤ 0.05; ∗∗p ≤ 0.01; n.s.: Not significant. Hsp90, heat shock protein 90; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.