Student Theses and Dissertations
Date of Award
1963
Document Type
Thesis
Degree Name
Doctor of Philosophy (PhD)
Thesis Advisor
Igor Tamm
Keywords
reovirus type 3, double-stranded RNA, icosahedral structure, erythrocyte agglutination, viral replication inhibition, genetic stability
Abstract
Reoviruses occur widely in the respiratory and enteric tracts of man and animals, but their relation to disease is not clear. The present study concerns the physical-chemical characteristics and interaction with cells of reovirus type 3. A main objective of the study is to relate some of the distinguishing biological characteristics of the virus to the structure of its RNA. Reoviruses are medium-sized, icosahedral viruses with a diameter of 75 mμ, and they contain RNA. The protein coat of the virus is composed of either 5- or 6-sided prismatic subunits, 92 in all. Each structural subunit of the protein coat is 75 A wide and possesses a hollow center 30 to 40 A in width and walls 15 to 20 A thick. Among the three immunological types of reovirus, all type 3 strains agglutinate bovine erythrocytes, and some agglutinate human erythrocytes. None of the strains of reovirus types 1 and 2 agglutinate bovine erythrocytes, whereas they all agglutinate human erythrocytes. The characteristics of reovirus type 3 interaction with receptor substances set it apart from all other viruses. The reactive groupings on reovirus 3 are sensitive to sulfhydryl reagents; they are also sensitive to trypsin, but resistant to chymotrypsin; they have the ability to react with neuraminic acid-containing glycoprotein receptors, but lack neuraminidase activity. The reproductive process of reovirus 3 is characterized by three features which distinguish it from other RNA viruses: 1. the multiplication of reovirus is relatively slow; 2. the inclusion which develops in reovirus-infected cells stains orthochromatically greenish-yellow with acridine orange, as if it contained DNA, yet it contains RNA; and 3. the multiplication of reovirus is inhibited by actinomycin D. Further evidence of the unusual characteristics of reovirus was obtained in studies of the synthesis of DNA, RNA, and proteins in infected and control cells. During the viral growth cycle, cellular DNA synthesis is specifically inhibited, whereas RNA and protein syntheses continue at normal levels. All of these results suggested that reovirus RNA may possess distinguishing structural features. The anomalous staining with acridine orange raised the possibility that reovirus RNA, unlike any other known RNA, may be double-stranded. Results of physical-chemical studies have provided strong evidence to support this view. Purified reovirus contains 14.6% RNA and no DNA. The sedimentation coefficient of the virus, s20=630 S, is consistent with a minimum particle weight of 70 x 106, and a minimum complement of RNA of 10 x 106 molecular weight units per particle. The base ratios are complementary. The mole percent, of G + C is 39.8. Reovirus RNA melts sharply with the Tm at 99°; it reacts minimally with formaldehyde at 32°; and is insensitive to the action of pancreatic ribonuclease. Thus reovirus RNA appears to have a secondary structure similar to that of DNA, namely a double-stranded helix. Both in this respect, and also with respect to the large amount of genetic material in the virus particle, reovirus is unique among animal viruses containing RNA. There is a second virus, the wound tumor virus, that has the same size and structure as reovirus. This plant virus produces tumors in sweet clover and other plants and is transmitted by an insect vector in which host it also multiplies. Wound tumor virus also has a ribonucleic acid component which melts sharply at a high temperature, and therefore may be a double-stranded helix. Tumor viruses so far studied all contain a relatively large amount of genetic material. As a repository for genetic information, the double-stranded helical structure may possess the necessary stability to insure continuity of the virus genome. All DNA tumor viruses have been shown to be double-stranded; all RNA tumor viruses may also be double-stranded.
License and Reuse Information
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Recommended Citation
Gomatos, Peter, "Animal and Plant Viruses with Double-Stranded Ribonucleic Acid" (1963). Student Theses and Dissertations. 518.
https://digitalcommons.rockefeller.edu/student_theses_and_dissertations/518
Comments
A thesis presented to the faculty of The Rockefeller University in partial fulfillment of the requirements for the degree of Doctor of Philosophy