STRUCTURAL AND CHEMICAL ARCHITECTURE OF HOST CELLS 143 



d. Treatment of protoplasts of B. fnegatherium with DNAase selectively 

 removed DNA in considerable amounts without affecting their abihty to 

 make /3-galactosidase (Landman and Spiegelman, 1955). 



On the other hand, the presence and concomitant synthesis of RNA are 

 variously reported to be essential to the production of particular enzymes, 

 although both requirements may not be necessary to all such syntheses, 



a. In the study of ultraviolet-irradiated yeast (Halvorson and Jackson, 

 1956), a dose that inliibited synthesis of a-glucosidase also inliibited protein 

 and RNA synthesis. 



b. An analog of uridine, 5-OH uridine, selectively uiliibits /3-galactosidase 

 production in E. coli without affecting over-all protem synthesis (Spiegelman 

 et at., 1955). Furthermore, this compound interrupts enzyme synthesis, even 

 after its onset, suggesting a requirement for continuing RNA synthesis for 

 enzyme production. 



c. A number of uracil-requiring bacterial mutants are unable to be induced 

 in the absence of this pyrimidine (Pardee, 1954). In one mstance, where a 

 uraciUess mutant can synthesize enzyme in the absence of exogenous uracil, 

 extensive turnover of RNA has been demonstrated (Earner and Cohen, 1958). 



d. Treatment of protoplasts of B. megaOierium with RNAase removes 80 

 to 90 % of the RNA without significant loss of DNA and protem; ^-galacto- 

 sidase production is also markedly inhibited (Landman and Spiegelman, 

 1955). Similar results are obtained with osmotically shocked protoplasts still 

 capable of enzyme synthesis (Spiegelman, 1957). 



6. Fractions of sonicaUy disrupted staphylococci are able to synthesize 

 various enzymes, such as catalase and ^-galactosidase. Removal of the 

 nucleic acids by nucleases reduces or aboUshes enzyme production. Addition 

 of intact RNA does promote the synthesis of catalase but not of ^-galacto- 

 sidase; however, provision of a mixture of purines and pyrimidines, per- 

 mitting C^*-uracil mcorporation into RNA, did stimidate synthesis of 

 ^-galactosidase (Gale, 1956), although it did not stimulate catalase synthesis. 

 It was concluded that a concomitant synthesis of RNA is essential to protein 

 synthesis in the latter case. 



f. In Staphylococcus aureus, RNA synthesis is not inhibited by azaguanme. 

 The induced formation of various enzymes is nevertheless strongly inliibited 

 by the presence of this analog (Greaser, 1955), and it is found that this com- 

 pound is incorporated into RNA. The formation of /8-galactosidase is far 

 more strongly inhibited by this agent than is catalase, particularly at certain 

 stages of bacterial growth. Gale has interpreted this to mean that existing 

 RNA templates may be adequate for the synthesis of some enzymes, such as 

 catalase, but that de novo RNA synthesis is essential for others, such as 

 /3-galactosidase. This difference may conceivably parallel the differences 

 between constitutive and inducible enzymes. 

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