THE AMINO-TERMINAL DELETION MUTANTS OF HEPATITIS-C VIRUS NONSTRUCTURAL PROTEIN NS5A FUNCTION AS TRANSCRIPTIONAL ACTIVATORS IN YEAST

To investigate the biological function of hepatitis C virus (HCV)-NS5A , the NS5A was fused at its N-terminus with the DNA binding domain (DB D) of yeast transcriptional activator GAL4 (GAL4-DBD). The GAL4-DBD al one had no transcriptional activation function. However, a mutant of t he GAL4-DBD/NS5A fusion protein, in which 129 amino acid residues were deleted from the N-terminus of NS5A, exhibited strong transcriptional activation in yeast cells, bearing the Escherichia coli lacZ reporter gene encoding the beta-galactosidase under the transcriptional contro l of GAL4 promoter and TATA box. Further mutational analysis of NS5A r evealed that the region between the amino acid residues 130 to 352 wer e critical for optimal level of transactivation. This region includes two acidic domains and one proline-rich region which have been shown t o be involved in the function of several transcriptional activators. ( C) 1997 Academic Press.