Die Bildung von RNS-Doppelstrang zur Vermehrung eines RNS enthaltenden Bakteriophagen

Abstract

The RNA phage fr induces in Escherichia coli cells the production of double stranded RNA, which is identified by its thermal denaturation profile ( T_m 101 °C in 0,2-m. Na^⊕ ), by its nonreactivity with formaldehyde and by its buoyant density in Cs₂SO₄ (1,609 g cm^-3 , compared to that of fr-RNA = 1,634 g cm^-3 ). Unless denatured the double strand is resistant to RNase. In its high molecular weight form the double stranded R N A has twice the weight of fr-RNA, as estimated from the sedimentation coefficient (s₂₀ = 14,5). The base ratios are those expected for a double stranded replicative from of fr-RNA. By melting and annealing one of the strands of the non-radioactive material can be exchanged for ³²P-fr-RNA from phage particles. Infectiosity of the doublestranded RNAhas not yet been shown. Extracts from infected cells contain double strand bound to the 30 - 50 s fraction; there is also double strand in the supernatant, apparently in the form of relatively low molecular weight fragments. The double stranded RNA, isolated at the height of infection, accounts for 3 - 8% of the cellular RNA. Cells infected with ³²P-fr show a surprisingly large part of the infecting RNA bound to ribosomes quite late in the latent phase. The meaning of this result is discussed.