Sequences within the VP6 molecule of bluetongue virus that determine cytoplasmic and nuclear targeting of the protein

Abstract

Genome segment 9 of bluetongue virus serotype 10 encodes the minor protein VP6. The protein is abundant with basic residues particularly in two regions of the carboxy half of the molecule. A series of amino-and carboxy-terminal deletion mutants was expressed in mammalian cells by using a vaccinia virus T7 polymerasedriven transient expression system, and the intracellular fate of the products was monitored by both immunofluorescence staining and cell fractionation techniques. Data obtained indicated clearly that VP6 has nuclear transportation signals which may be correlated with positively charged domains of the molecule. In the intact molecule, though, these signals are masked and the protein is retained in the cytoplasm. The biochemical and immunofluorescence data obtained indicate that sequences in the region of residues 33 to 80 of the 328-aminoacid protein are required for the retention of VP6 within the cell cytoplasm while amino acids 303 to 308 in the carboxy-terminal half of the molecule appear to possess nuclear localization capabilities.

Bluetongue virus VP6 protein binds ATP and exhibits an RNA-dependent ATPase function and a helicase activity that catalyze the unwinding of double-stranded RNA substrates

“…Clusters of RGG repeats have been proposed as an RNA-binding motif (20), as well as functioning as nuclear localization signals (32). Interestingly, with appropriate deletion mutations VP6 has been shown to possess nuclear localization signals (56), and one putative RNA-binding region has been identified in VP6 which contains an RGG site within an arginine-rich stretch. Whether this area constitutes the main RNA-binding site has yet to be elucidated.…”