CUCUMBER MOSAIC VIRUS-ASSOCIATED RNA-5 .6. CHARACTERIZATION AND DENATURATION RENATURATION BEHAVIOR OF THE DOUBLE-STRANDED FORM

The double-stranded form of cucumber mosaic virus-associated RNA 5 was purified and further characterized. Its MW determined by sedimentation equilibrium is 2.15 .cntdot. 105. The buoyant density calculated from its symmetrical distribution is Cs2SO4, following isopycnic ultracentrifugation, is 1.615 g/cm3. The sedimentation rate of double-stranded cucumber mosaic virus-associated RNA 5 is slightly greater than that of cucumber mosaic virus-associated RNA 5; its electrophoretic mobility in polyacrylamide gel (2.4%) is less than that of cucumber mosaic virus-associated RNA 5. By these standards the double-stranded cucumber mosaic virus-associated RNA 5 preparations used were homogeneous in size and density. Thermal denaturation monitored by means of ultraviolet light absorption produced multitransitional denaturation profiles. The average melting temperature (Tm) was 88.degree. C in 0.1 .times. SSC [1 .times. SSC = 0.15 M NaCl/0.015 M sodium citrate, pH 7.2]. Monotransitional denaturation profiles and slightly higher Tm values were obtained when resistance against RNase digestion was measured. These denaturation experiments and other properties showed that double-stranded cucumber mosaic virus-associated RNA 5 and the double-stranded form of peanut stunt virus-associated RNA 5 are small double-stranded nucleic acids with several homostable base-pair regions, characterized by distinct G + C contents and Tm values.