Caspase cleavage of viral proteins, another way for viruses to make the best of apoptosis

Richard, A; Tulasne, D

SARS-coronavirus (SARS-CoV) is a fairly new RNA virus responsible for a severe acute respiratory disease. SARS-CoV leads to either permissive or persistent infection, with strong cytopathic effects and high viral titers or the opposite, respectively. Interestingly, the nucleocapsid protein (N), that has both structural and non-structural functions, is proteolytically processed in cells undergoing a lytic cycle or ectopically expressing the protein. 29 Using a pharmalogical approach, N protein was demonstrated to be targeted by caspases 3 and 6. On permissive infection, N protein localizes in both cytosol and nucleus while remaining cytosolic in cells undergoing persistent infection. Moreover, preventing N from translocating to the nucleus by mutating its nuclear localization signal abolishes its cleavage by caspases. Thus, permissive infection is associated with N being translocated to the nucleus and possibly its ensuing caspase cleavage. Nevertheless, the mechanisms underlying viral replication, N subcellular localization and N caspase processing are unknown so far.