5′-Terminal Sequences of Spring Viremia of Carp Virus RNA Synthesized In Vitro

Abstract

Sequence analyses have been undertaken on the 5′ termini of the RNA species synthesized in vitro at 22°C by Spring viremia of carp virion (SVCV)-associated transcriptase by using virus grown in mammalian BHK-21 cells. SVCV product RNA was synthesized in the absence or presence of low (0.56 μM) or high (0.8 mM) concentrations of added S -adenosyl- l -methionine (SAM). Two major sequences obtained in the absence (or in low concentrations) of SAM have been shown to be GpppAp and GpppAmpAp(C). A minor sequence detected when a low concentration of [ 3 H]SAM was added to reaction mixtures was 7mGpppAmpAp. Larger quantities of the 7mGpppAmpAp(C) sequence, in addition to the GpppAmpAp(C) sequence, were obtained when high concentrations of SAM were used, and under these conditions no GpppAp sequences were detected. It has further been shown that with low concentrations of [ 3 H]SAM the principle in vitro methylation of adenosine in SVCV product RNA occurred at the 2′- O -ribose position; no methylation at the N 6 -adenosine position and no internal product RNA methylation were detected. Comparison of the SVCV results to the published data on the 5′-terminal structures of the in vitro or in vivo mRNA species of vesicular stomatitis virus Indiana and vesicular stomatitis virus New Jersey suggests that the 5′ sequences of transcript RNA of different rhabdoviruses may have been conserved.