INDUCED ENZYME FORMATION 



hardly lend support to the supposition that it is. The credence 

 assignable to such negative conclusions with respect to DNA 

 gains further weight from similar experiments examining RNA 

 metabolism which yielded strikingly different results 



RNA AS A COMPONENT OF EFS 



Many have postulated RNA as a key substance in protein 

 synthesis. Chantrenne (14) has succinctly summarized such 

 speculations and the supporting evidence. Here we would like 

 to confine our attention to the information derived from the 

 study of enzyme synthesis. Again, as in the case of DNA, 

 correlative experiments have been performed with intact cells 

 examining the effects on enzyme formation of agents or condi- 

 tions which influence RNA metabolism. 



7. Experiments with Ultraviolet Light. Swenson and Giese 

 (94,95) demonstrated that exposure to ultraviolet dosages far 

 exceeding those required to stop DNA formation, results in the 

 inhibition of induced enzyme synthesis in yeast. Examination 

 of the action spectrum of the inhibition revealed that it coincided 

 with the absorption spectrum of nucleic acid. Halvorson and 

 Jackson (31) extended these interesting observations. They 

 examined the effects of various dosages on the synthesis of alpha- 

 glucosidase, the ability to use free amino acid pool components, 

 and the incorporation of P^^ into the nucleotides of RNA. Their 

 results established an excellent parallelism between the loss in 

 capacity to utilize the free amino acids and the ability to syn- 

 thesize enzyme. It was further found (85) that even slight dam- 

 age of RNA metabolism, as measured by ability to incorporate 

 P^-, had profound effects on enzyme-forming ability. Thus, at 

 a dose which achieved a 22 per cent inhibition of RNA metabo- 

 lism enzyme formation was suppressed to the extent of 95 per 

 cent. 



2. The Effect of a Uridine Analogue on Enzyme Synthesis. One 

 obvious approach which could in principle yield informa- 

 tion pertinent to the role of RNA is to examine the effects of 

 various analogues of uracil and its derivatives on enzyme forma- 



151 



