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Cell entry of Simian Virus 40 (SV40) involves caveolar/lipid raft-mediated endocytosis, vesicular transport to the endoplasmic reticulum (ER), translocation into the cytosol, and import into the nucleus. We analyzed the effects of ER-associated processes and factors on infection and on isolated viruses and found that SV40 makes use of the thiol-disulfide oxidoreductases, ERp57 and PDI, as well as the retrotranslocation proteins Derlin-1 and Sel1L. ERp57 isomerizes specific interchain disulfides connecting the major capsid protein, VP1, to a crosslinked network of neighbors, thus uncoupling about 12 of 72 VP1 pentamers. Cryo-electron tomography indicated that loss of interchain disulfides coupled with calcium depletion induces selective dissociation of the 12 vertex pentamers, a step likely to mimic uncoating of the virus in the cytosol. Thus, the virus utilizes the protein folding machinery for initial uncoating before exploiting the ER-associated degradation machinery presumably to escape from the ER lumen into the cytosol.

Original publication




Journal article



Publication Date





516 - 529


Cysteine, Disulfides, Endoplasmic Reticulum, HeLa Cells, Humans, Isomerism, Polyomavirus Infections, Protein Disulfide-Isomerases, Protein Folding, Protein Processing, Post-Translational, Protein Structure, Quaternary, Simian virus 40, Sulfhydryl Compounds, Tumor Virus Infections, Viral Proteins, Virion, Virus Internalization