VIII. PROTEIN SYNTHESIS AND GENE ACTION 389 



DNA or synthetic deoxypolymers, the complementary RNA is produced 

 (see Chamberlin and Berg, 1962, for references and recent results). 

 Bautz and Hall (1962) have suggested that in the intact cell only one 

 of the two strands of DNA is active, since the T4-specific RNA they 

 isolated did not have the composition of the DNA. The solution to this 

 question is critical to the understanding of the mechanism of infomia- 

 tion transfer and it is likely that these answers will come from further 

 studies of DNA-directed protein synthesis in cell-free systems. 



Studies of the cell-free synthesis of a specific protein, ;8-galactosidase, 

 were reported by Kameyama and Novelli (1960). This cell-free system 

 from E. coli produced a net increase in ^-galactosidase activity. Addi- 

 tion of DNase resulted in complete inhibition of enzyme synthesis, 

 accompanied by an 85% inhibition of amino acid incorporation into 

 total protein (Novelli et al., 1962). After X-irradiation of E. coli syn- 

 thesizing ^-galactosidase constitutively, the combined ribosomal and 

 supernatant fractions were unable to synthesize ^-galactosidase. Addi- 

 tion of DNA isolated from cells constitutive for ^-galactosidase syn- 

 thesis, or from induced cells, repaired the lesion introduced by X-irradia- 

 tion. DNA isolated from non-inducible cells was ineffective, providing 

 a control for non-specific effects of added DNA. In addition, in order 

 for DNA from inducible cells to stimulate ;8-galactosidase synthesis, the 

 DNA must be prepared from preinduced cells. This finding would be 

 consistent with the concept of repressors acting at the gene level (Jacob 

 and ]\Ionod. 1961). However, the ribosomes used must also come from 

 preinduced cells, which suggests perhaps that specific ribosomes are 

 synthesized during preinduction. The results discussed previously have 

 indicated a lack of specificity of the ribosome and, in fact, suggest that 

 all types of proteins can be made in any population of ribosomes de- 

 pending on the messenger RNA provided. Even when all the components 

 of the system for /3-galactosidase synthesis came from preinduced cells, 

 inducer was required for cell-free synthesis of ^-galactosidase (Novelli 

 et al., 1962). This suggested production of repressor in the system under 

 the influence of the i"^ gene (Jacob and ]Monod. 1961). Indeed, when all 

 the constituents came from r cells, (constitutive mutant) inducer was 

 not required and DNA from r cells, not induced, was inhibitoiy. This 

 result was interpreted as indicating a binding of repressor to DNA. 

 These results represent a remarkable advance in the understanding of 

 induced enzyme synthesis. They differ enough from other results that 

 confirmation in other laboratories would be desirable. Also, since there 

 is always a considerable amount of preformed enzyme present at the 

 start of the experiment, the usual enzyme synthesis measured is only a 

 doubling of that already present. However, careful immunological and 



