48 RIBONUCLEIC ACIDS AND PROTEIN SYNTHESIS 



pense of free amino acids, without the formation of peptides as 

 intermediates. The fact is now well established in the case of induced 

 enzyme synthesis in microorganisms, as well as in the tissues of 

 higher organisms. 



While there is no evidence to prove conclusively that RNA is the 

 template, many experimental results fit in well with this hypothesis. 

 For instance, it has been demonstrated that in pancreatic tissue 

 which has been stimulated to enzyme production by pilocarpine 

 (Hokin, 1952; De Deken-Grenson, 1953a, b) and in the secreting 

 oviduct of laying hens (Grenson, 1952), the synthesis of proteins is 

 not linked to the rate of uptake of ^^P by RNA. These observations 

 are in better agreement with the template hypothesis than with any 

 other. As Hokin (1952) points out, it would seem that RNA plays a 

 part during the rearrangement and movement of enzymes during 

 secretion. Nucleoproteins or RNA might act as a specific frame- 

 work on to which enzyme systems could be organized and which 

 could direct the synthesis of more RNA. Such a view is consistent 

 with the results of Daly and Mirsky (1952) which indicate that the 

 total protein content of the pancreas remains constant during the 

 cycle of secretion and synthesis. When enzyme secretion takes place, 

 rapid synthesis of a precursor protein would occur and this would 

 be followed by gradual transformation into the characteristic pan- 

 creatic enzymes. 



Some evidence for the template theory has been introduced by 

 Gale and Folkes (1955b). They also showed that in their above- 

 mentioned experiments with disrupted staphylococci, RNA could 

 be replaced by small fragments obtained by ribonuclease digestion 

 of the whole RNA molecule. As pointed out by Gale (1956a, b), 

 these results might be explained on the assumption that "complete 

 nucleic acid may present a linked series of specific loci each of 

 which corresponds to the position of a specific amino acid in a 

 protein sequence. The promotion of incorporation by exchange 

 would thus depend upon the order of the loci in a particular nucleic 

 acid, and the species specificity of undigested nucleic acids in this 

 respect would be explained." 



Still another observation, which agrees well with the template 



