Polyadenylic acid sequences in the genomic RNA of the togavirus of simian hemorrhagic fever

Abstract

Since serologic studies have failed to relate the togavirus simian hemorrhagic fever (SHF) virus to any currently accepted genus within the Togaviridae family, the presence of polyadenylic acid (poly(A)] in the genomic RNA was analyzed in view of the different content reported for the two major genera of that family: alphaviruses where poly(A) is 40 to 120 nucleotides long and flavivirus where poly(A) is considered to be absent. Oligo(dT)-cellulose chromatography of whole genomic RNA from purified SHF virus revealed that about 36% of the molecules contained segments of poly(A) of sufficient length to bind to oligo(dT)-cellulose. However, a reproducible fraction of the RNAs did not bind to oligo(dT)-cellulose, indicating little or no poly(A) present. When analyzed by electrophoresis under denaturing conditions, both the binding and nonbinding molecules were similar in size. In addition, no polyuridylic acid [poly(U)] was detected in SHF virus genomic RNA. After digestion of the genomic RNA with pancreatic and T 1 ribonucleases, the resultant resistant polynucleotide sedimented by ultracentrifugation between tRNA and 5 S RNA. Base composition analysis of these polynucleotides detected only adenosinic residues. A mean length of 76 ∼2 nucleotides for these poly(A) sequences of SHF virus RNA was established by electrophoresis under denaturing conditions. Thus, together with previous morphological as well as biochemical findings, the presence of a poly(A) sequence is further evidence that SHF virus has distinctive characteristics which differentiates it from the two major subgroups of togavirus.