33. NUCLEIC ACIDS OF THE BACTERIAL VIRUSES 215 



TABLE III 

 Composition of Various Nucleic Acids 



References 

 " E. Volkin and L. Astrachan, Virology 2, 149 (1956). 

 6 G. R. Wyatt and S. S. Cohen, Biochem. J. 55, 773 (1953). 

 c E. Volkin, L. Astrachan, and J. L. Countryman, Virology 6, 545 (19581 . 



RNA proceed at a faster rate than de novo synthesis of DXA (much of the 

 T7 DNA is derived from preinfection host nucleic acids). Thus, in this in- 

 stance conversion of RNA polymer to DNA polymer could occur, but this 

 could not be the only manner of turnover of RNA. 



The most unusual aspect of the RNA metabolism of phage-infected cells 

 is the close relationship between the nucleotide composition of the new RNA 

 and the nucleotide composition of the DNA of the infecting phage. 129 • 129a • 131 

 If it is assumed that only wholly new RNA molecules are made after infec- 

 tion, then, by alkaline degradation to 2'- and 3'-mononucleotides, fractiona- 

 tion, and measurement of the total radioactivity associated with each 

 nucleotide, the relative nucleotide composition of the new RNA can be 

 determined. Since the bulk RNA nucleotide composition of the cell does 

 not change during infection, and since the nucleotides are present in nearly 

 equal proportion, measurement of the relative specific activities of the 

 labeled nucleotides is sufficient to approximate the relative composition of 

 the new RNA. As shown in Table III, this composition remarkably paral- 

 lels the composition of the phage DNA. 



This interesting correlation of RNA and DNA compositions might simply 

 reflect the availability of precursors for RNA and DNA. Alternatively there 

 is the more significant possibility that the RNA made after infection is 

 patterned on the phage DNA and is an intermediary in the synthesis of 

 phage proteins and specific enzymes related to the infective process. 



The addition of chloramphenicol before infection prevents this shift of 

 the nucleotide composition of RNA synthesis during infection. 133 Upon 

 infection in the presence of chloramphenicol, RNA synthesis is observed 

 at a greater rate than during normal infection, but the composition of the 

 synthesized RNA remains that of normal coli RNA, 133a and this RNA does 

 not turn over. 



133 L. Astrachan and E. Volkin, Biorhim. et Biophys. Acta 32, 449 (1959). 



133a Contrary results have been reported by Watanabe el a/. 129H This contradiction 



