Figure 1.

ORF57 enhances translation of an intronless viral mRNA. (Ai) Intronless KSHV gM RNA was transcribed in vitro and equal amounts carried over into ³⁵S-methionine-labelled in vitro rabbit reticulocyte translation reactions, spiked with increasing amounts (0.5, 1 or 2.5 μg) of either purified bunyamwera virus nucleocapsid protein, GST-PYM, GST-ORF57 or GST-PYMΔC. (Aii) Luciferase RNA was transcribed in vitro and equal amounts carried over into ³⁵S-methionine-labelled in vitro rabbit reticulocyte translation reactions, spiked with increasing amounts (0, 1 or 2.5 μg) of GST-PYM or GST-ORF57. (Aiii) gM or luciferase RNA was transcribed in vitro and equal amounts were carried over into ³⁵S-methionine-labelled in vitro human cell extract translation reactions, spiked with increasing amounts (0, 1 or 2.5 μg) of GST-ORF57. Translation reactions were separated by SDS–PAGE and proteins detected by autoradiography and quantified by densitometry. (B) Cytoplasmic lysate from reactivated BCBL-1 cells treated with cyclohexamide was separated by sucrose gradient fractionation in the presence of 20 mM EDTA. Fractions were analysed for rRNA and protein content by agarose gel electrophoresis or western blot analysis, respectively.