RNA, phages

Since all members of this family of RNA phages have homologous coat proteins, their subunits are expected to have the same three-dimensional structure. It remains to be seen if the MS2 fold is also present in any other unrelated viruses. The fold is so far unique for the MS2 subunit, but similar structures have been observed in other proteins such as the major histocompatibility antigen, HLA, which was discussed in Chapter 15. 

The bacterial RNA viruses are all of quite small size, about 26 nm in size, and they are all icosahedral, with 180 copies of coat protein per virus particle. The complete nucleotide sequence of several RNA phages are known. In the RNA phage MS2, which infects Escherichia coli, the viral RNA is 3,569 nucleotides long. The virus RNA, although single stranded, has extensive regions of secondary and tertiary structure. The RNA strand in the virion has the plus (+) sense, acting directly as mRNA upon entry into the cell. 

Escherichia coli (strain JE24F+, derived from W3110, uninfected or infected with RNA-phage MS2 [2] recombinant overproducing strains [29,30] K-12 strains [30]) [2, 3, 28-31, 61, 62, 68, 70, 71]... 

Hiraga, S. Sugino, Y. Nucleoside monophosphokinases of Escherichia coli infected and uninfected with an RNA phage. Biochim. Biophys. Acta, 114, 416-418 (1966)... 

Withered, G.W., Gott, J.M. and Uhlenbeck, O.C. (1991) Specific interaction between RNA phage coat proteins and RNA. Prog. Nucleic Acid Res. Mol. Biol., 40, 185-220. 

Protomembranes protected the first genetic system. The protomembrane consisted of a lipid bilayer similar to that of the PM2 vims. A corresponding bilayer of an RNA phage did not survive, unfortunately (Fliigel 2010). 

Soon after T4 phage has infected E. coli, host protein synthesis is inhibited and the bacterium cannot be superinfected with RNA phage. This is reflected by the inability of ribosomes from T4 infected E. coli to translate MS2, f2, or R17 RNA in vitro or to bind to the initiation sites at the beginning of each cistron (Dube and Rudland, 1970 Steitz et al., 1970 Hsu and Weiss, 1969 Klem et al, 1970). If ribosomes from infected cells are washed in 2.0 M NH,C1 and then supplemented with initiation factors from normal ribosomes they are once more able to translate phage RNA. On the other hand, the wash fraction from infected ribosomes prevents, and even reverses, the formation of initiation complexes between normal ribosomes and MS2 RNA. These observations suggest that after T4 infection E. coli initiation factors are selectively... 

Hie replicase of virus Q() (an RNA-phage) consists of four subunits one is encoded by the vM genome, wliile tlie other three are the host proteins EFTu, EFTs and R.p. SI. The Fig. shows a three dimensional model for the arrangement of R.p. in the SOS-subunit. Many antibiotics act by combining with R.p., e.g. streptomycin interacts with S12, and bacterial mutants resistant to streptomycin have been shown to liave an altered S12. Erythromycin interacts with L22, spiramycin with LA. 

Weissmann, C., Simon, L., Borst, P. and Ochoa, S., Induction of RNA synthetase in E. coliafter infection by the RNA phage, MS2. Cold Spring Harbor Symposia on Quantitative Biology, 28, 99 (1963). 

Some time before we left N. Y.U. we had to face the problem of what kind of work to do in Madrid. To continue the work on RNA phages or on protein synthesis, which we had carried out in New York, was quickly dismissed. We had to set up our laboratory starting with an empty room and we knew that it would take some time before we could get things in full operation. 

Murata, A, Kitagawa, K., Inmaru, H., and Saruno, R. (1972) Inactivation of single-stranded DNA and RNA phages by ascorbic acids and thiol reducing agents, Agr. Biol, Chem. 36 2597-2599. 

One of the simplest viruses known is the bacteriophage Qg. It belongs to a class of single stranded RNA phages with very similar properties. The phage MS2 belongs to this family and is a close re-... 

Fig. 15. RNA-phage infection of a bacterial cell as a simple hyper-cyclic process. Using the translation machinery (T) of the host cell the infectious plus strand (I ) first instructs the synthesis of a protein subunit which associates with three host proteins to form a phage-specific RNA-replicase. This replicase complex (R) exclusively recognizes both phage-RNA strands, plus and minus, and replicates them.

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