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and the onset of protein synthesis, but if we could overlook this interlude, the data 

 would tell us that the cells are building up a maximum concentration of RNA before 

 undertaking protein synthesis at a maximum rate. From the ameba's standpoint, the 

 fact that RNA is laid down before division might mean that it can avoid a lag in protein 

 synthesis after division. The data tell us that there is no net increase in RNA per cell 

 during the period of rapid protein synthesis. They tell us nothing about turnover. 



SPIEGELMAN: Let's imagine that RNA is actually destroyed whilemaking 

 protein. Then the rate in that steady state might acuta Uy be faster than during the 

 rise. 



MAZIA: That could be. These data deal only with absolute amounts of RNA, 

 and only tell us that the cell does not require a higher level of RNA during net protein 

 synthesis than existed before division when net protein synthesis was not taking place. 



POLLARD: Let me ask a question. Was it your preconceived idea that 

 you don't want this to be destroyed? 



MAZUV: I was coming to thatDr. Pollard. There is a lot of circumstantial 

 evidence relating RNA to protein synthesis, but many of the people who work on it fail 

 to distinguish between three entirely different things; a relation between RNA and 

 protein synthesis, a relation between RNA synthesis and protein synthesis, anda re- 

 lation between RNA turnover and protein synthesis. I have never head a discussion of 

 this important problem where these three kinds of relations have been distinguished 

 sharply. 



CARTER: A gland stimulated to secrete a great deal of protein hor- 

 mone must be synthesizing protein at a rapid rate and yet it shows no change in 

 rate of nucleic acid turnover, measured with one or two precursors. 



MAZIA: That does not dissociate the synthesis from the RNA that is there. 

 That is my point. 



CHARGAFF: I think there is very little evidence either for or against it. 



SPIEGELMAN: Well, I will cite some evidence. 



CHARGAFF: For RNA being responsible for protein synthesis? 



SPIEGELMAN: The evidence available cannot be taken as establishing with 

 certainty that RNA is responsible for protein synthesis, but I believe that the experi- 

 ments are suggestive. The data I shall be concerned with deal primarily with the syn- 

 thesis of certain enzymes. 



A variety of enzymes has been studied, including 6-galactosidase of 

 E . coli and a-glucosidases of yeast. I might, perhaps, begin by noting that evi- 

 dence concerning the nature of the precursor that is converted into active enzyme 

 appears to be quite definitive. The work in Monod's laboratory on the synthesis 

 of (3-galactosidase in E. coli, and our own work on this system, as well as the q- 

 glucosidases of yeast, indicate that the cell uses free amino acids in putting en- 

 zyme molecules together. There are no indications of peptide involvement. The 

 data support rather the simultaneous utilization of the constituent amino acids. 

 This view already has implications for the enzyme-forming mechanism. If one 

 is to look for the machinery that puts the protein together, it obviously has to be 

 as big and as complex as the thing that is being synthesized if this view of protein 

 synthesis is correct. As long as one could imagine a step-wise mechanism, the 



