32 RIBONUCLEIC ACIDS AND PROTEIN SYNTHESIS 



fortunately, it has been impossible so far to establish its chemical 

 nature. 



Some of Gale and Folkes' (1954, 1955a) results have been quickly 

 confirmed on a different system, the so-csiWed protoplasts. These are 

 bacteria (Micrococcus lysodeikticus, B. megatherium, etc.) which 

 have been treated with lysozyme in sucrose solutions. The bacterial 

 outer membrane is dissolved by such a treatment, but the rest of the 

 protoplasm remains intact. Protoplasts constitute a very favorable 

 system, which can be resolved by treating them with ribonuclease. 

 Treatment of protoplasts with ribonuclease strongly inhibits the 

 incorporation of amino acids into the proteins, while deoxyribonu- 

 clease stimulates this process (Lester, 1953; Beljanski, 1954). The 

 ribonuclease treatment has no effect on the respiration of the pro- 

 toplasts, according to Beljanski (1954). 



But the most interesting results obtained so far on protoplasts 

 are probably those of Landman and Spiegelman (1955) and of 

 Spiegelman (1956). Protoplasts, if suitably isolated, are still capable 

 of induced enzyme synthesis, as shown also by Wiame et al. (1955). 

 /5-Galactosidase synthesis was induced by Landman and Spiegel- 

 man (1955) with B. megatherium protoplasts; hexose diphosphate 

 was added as an energy source and amino acids were present. This 

 specific enzyme induction is almost completely inhibited by ribo- 

 nuclease (1 mg/ml), which removes 80-90% of the protoplasts* 

 RNA. In contrast, deoxyribonuclease has a stimulating effect on 

 the synthesis of /5-galactosidase. Even when 20-25 % of the DNA 

 has been removed from the protoplasts by deoxyribonuclease treat- 

 ment, induced enzyme synthesis proceeds normally. The experi- 

 ments clearly show that the integrity of RNA is more important 

 than that of DNA for protein synthesis. 



These observations raise a new and important question for the 

 cell physiologist: is it possible to inhibit growth and protein syn- 

 thesis in living cells or organisms by an appropriate ribonuclease 

 treatment? 



This problem has been extensively studied in the author's labora- 

 tory during the past few years. Starting from observations by 

 Lansing and Rosenthal (1952), who found that ribonuclease treat- 



