198 S. S. COHEN 



In addition, increasing evidence, although as yet sparse and unconfirmed, 

 have indicated a nuclear involvement in the multiplication of some ENA 

 viruses, such as influenza and poliomyelitis. It would therefore be important 

 to know if RNA viruses can multiply in enucleate cells or if other evidence 

 can be obtained to eliminate the participation of DNA in such 

 multiphcation. 



The conclusion that RNA can control the synthesis of protein stems from 

 the following classes of data: 



a. Protein is made in enucleate ceUs lacking DNA; its synthesis is inhibited 

 by ribonuclease treatment of such cell fragments. 



b. Inliibition of RNA synthesis in genetically blocked, nutritionally de- 

 ficient, or otherwise inhibited systems blocks protein synthesis. 



c. Protem synthesis is most active in cell organelles possessing the highest 

 RNA content. 



d. Protein synthesis in vivo involves the formation of ammo acid adeny- 

 lates, the intermediate transfer of the amino acids to RNA, which then 

 shuttles them to the ribonucleoprotein portions of the microsomal 

 fraction. Ammo acid incorporation is prevented by the action of 

 ribonuclease. 



Amino acids play a catalytic role in RNA synthesis in cells and cell frac- 

 tions. In cells a gross inhibition of protein synthesis by chloramphenicol does 

 not inhibit RNA synthesis, but the lack of availabihty of an amino acid can 

 eliminate this function. It may be inferred that the amino acids are essential 

 for some stages of nucleotide activation or transfer, as has indeed been 

 reported. 



Specific enzyme production in cell fragments (protoplast membranes) 

 almost devoid of DNA has been reported by Spiegelman (1957). Ribonu- 

 clease, but not deoxyribonuclease, destroys the abihty of the fragment to 

 produce j8-galactosidase. However, since the fragments retain the abihty to 

 synthesize DNA under conditions of enzyme synthesis, the significance of 

 these very interestmg results is obscured. 



Some workers have suggested that the primary template in protein 

 synthesis is protein itself (Haurowitz, 1950). Smce its duplication must occur 

 in an unfolded state, it is supj)osed that the role of the nucleic acids is merely 

 to maintain the template protein film in the expanded state. However, the 

 activity of transforming DNA and the infectivity of viral nucleic acids 

 affirms the specificity of these substances. It wiU be assumed in this discus- 

 sion, then, that RNA may be a primary template and that the RNA in micro- 

 somal preparations plays a specific role in organizing the synthesis of specific 

 arrays of peptides. 



The following variations have been proposed concerning the mode of 

 action of the RNA template in organizing protein synthesis: 



