Sindbis virus variant with a deletion in the 6K gene shows defects in glycoprotein processing and trafficking: lack of complementation by a wild-type 6K gene in trans.

A Sindbis virus (SV) variant with a 6K gene partially deleted has been obtained. This SV Del6K virus is defective in the proteolytic processing of virus glycoprotein precursor, transport of glycoproteins to the plasma membrane, and plaque phenotype. A revertant virus (SV Del6K-revQ21L) containing a point mutation in the deleted 6K gene was isolated and characterized. SV Del6K-revQ21L has corrected the defects of proteolytic processing and transport of virus glycoproteins to the plasma membrane, but it still remains attenuated compared to wild-type (wt) SV, exhibiting defects in virus budding. Neither mutant nor revertant viruses are complemented by the coexpression in trans of a wt SV 6K gene.