294 HEINZ SCHUSTER 



nucleic acid which can induce leukemia by detergent, extraction of leukemic 

 cells of mice can also be only briefly mentioned since it was not decided 

 whether the active agent was RNA or DNA. 



2. Arrangement of the Ribonucleic Acids in Animal Viruses 



In most cases in which animal viruses have been morphologically and 

 chemically characterized in some detail, it has been shown that the RNA 

 is in the interior of the infectious particle. The best demonstration of this 

 is the resistance of the virus particles to ribonuclease treatment. For ex- 

 ample, the infectivity of poliovirus is not altered when the virus solution 

 is incubated with ribonuclease during the purification procedure. 27 After 

 removal of virus protein by phenol treatment, the infectious virus ma- 

 terial in the aqueous phase is highly sensitive to ribonuclease. 157 ' 158, 159 

 During the purification of poliovirus, a noninfectious component was iso- 

 lated which sediments more slowly than the infectious component. The 

 former has little or no RNA and has been observed in the electron micro- 

 scope as a round flattened particle of somewhat larger diameter than the 

 infective particle. This component seems to be composed mainly of protein 

 and is very similar to the noninfectious nucleic acid-free particle of turnip 

 yellow mosaic virus. 160 



The arrangement of RNA in the more complex viruses has only been 

 studied in some detail for several representatives of the myxovirus group. 

 Influenza and fowl plague viruses, which belong to this group, contain RNA, 

 protein, and carbohydrates. Two subunits of different composition could 

 be distinguished in these viruses; the virus hemagglutinin which contains 

 only protein and carbohydrate, and the so-called g-antigen which contains 

 protein and all the RNA of the virus. The hemagglutinin must be part of 

 the surface of the whole particle since it possesses the biological surface 

 characteristics of the infective particle. The ribonucleoprotein component, 

 which is antigenic, is only detectable in appreciable amounts after the 

 particles are carefully disrupted. 



By electron microscopic studies of the virus after degradation with en- 

 zymes, it may be concluded that the virus particle has an external shell of 



165 R. Latarjet, N. Rebeyrotte, and E. Moustacchi, Compt. rend. acad. sci, 246, 853 

 (1958). 



156 E. F. Hays, N. S. Simmons, and W. S. Beck, Nature 180, 1419 (1957). 



157 G. Koch, H. E. Alexander, I. M. Mountain, K. Sprunt, and O. Van Damme, 

 Federation Proc. 17, 256 (1958). 



158 H. E. Alexander, G. Koch, I. M. Mountain, K. Sprunt, and O. Van Damme, 

 Virology 5, 172 (1958). 



159 H. E. Alexander, G. Koch, I. M. Mountain, and (). Van Damme, J. Exptl. med. 

 108, 493 (1958). 



160 R. Markham, Discussions Faraday Soc. 11, 221 (1951). 



