Proteolytic cleavage and viral proteins
Stanislav V. Sosnovtsev
from: Caliciviruses: Molecular and Cellular Virology (Edited by: Grant S. Hansman, Xi Jason Jiang and Kim Y. Green). Caister Academic Press, U.K. (2010)
Caliciviruses are icosahedral nonenveloped viruses with a positive-sense single strand RNA genome that does not exceed 8.6 kb. Despite its small size, the virus genome encodes a number of nonstructural proteins that successfully facilitate and regulate mechanisms required for efficient virus amplification. Although caliciviruses show significant genetic diversity, they share a common protein expression strategy. Recent findings have shown that the nonstructural proteins of caliciviruses are produced by autocatalytic cleavage of a polyprotein encoded by ORF1 of the virus genome. A single virus protease structurally similar to a class of viral chymotrypsin-like cysteine proteases mediates these cleavages, and in some caliciviruses, adds to a release of the virus capsid protein. The temporal regulation of viral protein synthesis relies on the specificity of the protease and may be modulated by additional viral and cellular factors. The proteolytic processing results not only in the synthesis of the mature virus proteins, but also their precursors, whose functions have yet to be determined. Almost all calicivirus proteins have been identified as components of the virus replication complexes; however, their roles in replication are not entirely understood and remain an active and crucial target of calicivirus research read more ...