5′-terminal structure of messenger RNA transcribed by the RNA polymerase of silkworm cytoplasmic polyhedrosis virus containing double-stranded RNA

Abstract

The RNA polymerase in silkworm cytoplasmic polyhedrosis virus particle transcribed the nucleotide sequence of one chain of the double-stranded RNA genome, which consists of ten segments. The radioactivity of [ β - 32 P]ATP was incorporated into the 5′-terminus of the product messenger RNA, but γ -phosphate of ATP or β -phosphate of GTP was not found in the RNA. The transcribed RNA, which carries [ β - 32 P]diphosphate at the 5′-terminal adenylic acid, was analyzed. A unique sequence ppApGpPyp- was identified as the 5′-terminus of every mRNA that was transcribed from every genome segment. It is concluded that, of the two genome strands, one chain carrying uracil at the 3′-terminus is selected as a template and is transcribed from the terminal nucleotide.