Reoviruses, mammalian

More recently, triple /1-spiral repeats have been identified in mammalian reovirus type 3 fiber (Chappell et al., 2002 Fig. 4A), avian reovirus fiber (Guardado Calvo et al., 2005 Fig. 4B), and bacteriophage PRD1 P5 protein (Merckel et al., 2005 Fig. 4C). In the latter two cases, it appears that only two repeats are present, just N-terminal to the head domain. Mammalian reovirus fiber contains eight putative triple /1-spiral repeats, of which three were resolved in the crystal structure (Chappell et al., 2002). 

Baneijea, A. C., Brechling, K. A., Ray, C. A., Erikson, H., Pickup, D. J., andjoklik, W. K. (1988). High-level synthesis of biologically active reovirus protein crl in a mammalian expression vector system. Virology 167, 601-612. 

Harrison, S. J. et al. Mammalian reovirus L3 gene sequences and evidence for a distict amino-terminal region of the 1 protein. Virology 258, 54-64 (1999). 

Sharpe, A. H., Chien, L. B., and Fields, B. N., 1982, The interaction of mammalian reoviruses with the cytoskeleton of monkey kidney CV-1 cells. Virology 120 399. 

It is well known that synthetic or natural dsRNAs can serve as potent inhibitors of protein synthesis in various in vitro translation systems derived from mammalian cells (Ehrenfeld and Hunt, 1971 Kaempfer and Kaufman, 1973). A variety of other viral dsRNAs inhibit cell-free protein synthesis. The presence of dsRNA has also been detected by crosslinking experiments in HeLa cells infected with en-cephalomyocarditis virus or the t G114(I) mutant of VSV (Nilsen et al., 1981). Reovirus mRNA and polyadenylated vaccinia RNA transcribed in vitro have both been shown to contain dsRNAs which inhibited protein synthesis in cell-free systems (Baglioni et al., 1978 McDowell et al., 1972). Studies such as these with viruses other than rhabdoviruses are discussed in other chapters of this volume. The question that must be kept in mind is whether the in vitro inhibition of translation initiation by VSV dsRNA or any other viral dsRNA truly represents the sequence of events that takes place in the virus-infected cell. 

McDowell, M. J., Joklik, W. K., Villa-Konisofif, L., and Lodish, H. F., 1972, Translation of reovirus mRNAs synthesized in vitro into reovirus polypeptides in several mammalian cell-free extracts, Proc. Natl. Acad. Sci. USA 69 2649. 

The mammalian reoviruses are divided into three serotypes (1, 2, and 3) on the basis of hemagglutination inhibition and antibody neutralization tests (Rosen, 1960). Reovirions contain a segmented, double-stranded RNA (dsRNA) genome surrounded by two concentric icosahedral protein shells (Gomatos et ai, 1962). There is an internal core containing the genome and a closely applied inner capsid surrounded by an outer capsid shell (Smith et ai, 1969 Fig. 1). 

Fig. 1. Schematic diagram of the outer capsid of a mammalian reovirus. (Left) A negative stain electron micrograph of an intact virion. (Top right) A schematic drawing of the icosahedral reovirion, showing the organization of capsomeres. (Bottom) A schematic drawing that indicates the organization of the three outer capsid proteins 0-1, a3, and xlC. The al protein is located at the vertices of the icosahedron while 0-3 and xlC are associated with each other (in ratio of one xlC to two a3) on the flat surface of the icosahedron. From Fields (1982), by permission of Archives of Virology.

Using a genetic approach, Sharpe and Fields (1982) also have examined the effects of the mammalian reoviruses on host cell protein synthesis. Reovirus type 2 was found to inhibit protein synthesis in L cell monolayers more rapidly and efficiently than reovirus type 1 or 3. Type 2 reovirus also inhibits protein synthesis in human amnion cells (Loh and Soergel, 1967). The capacity of type 2 reovirus to... 

During the course of viral infection, the mammalian reoviruses alter the host cells in several ways reoviruses alter host cell metabolism and alter the organization of the cytoskeleton. 

Hand, R., and Tamm, I., 1974, Initiation of DNA synthesis in mammalian cells and its inhibition by reovirus infection, J. Mol. Biol. 82 175. 

The anti-poly I poly C antibodies react not only with RNA of reovirus but also, though to a lesser degree, with RNA extracted from mammalian cells (Fig. 4). Comparison of the efficiency of inhibition of the cross-reaction with mammahan RNA by RNA of reovirus, by double-helical complexes of synthetic polynucleotides and by single-stranded polynucleotides, has shown that the antibodies anti-poly I poly C react especially with double-stranded conformational determinants of the RNA. None of the single-stranded polynucleotides is capable of totally inhibiting the reaction with RNA whatever... 

Anti-poly A poly U antibodies also react with natural polynucleotides, including reovirus RNA, tRNA and ribosomal RNA from mammalian cells. Inhibition studies have shown that the poly A poly U absorbs all the antibodies reacting with RNA from mouse ascites cells. 

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