56 MAURICE J. be:ssman 



TABLE XXVII 

 Primer Differences of T2 and Escherichia coli Polymerases" 



" From Aposhian and Kornberg (1962). 



* In Experiment 1 , 0.09 ng of T2 jmI ymerase or 0. 10 mS of E. coli polymerase was 

 used. In Experiment 2, twice the amount of enzj'me was used. The labeled substrate 

 was C'-dGTP. 



How these properties of the induced polymerase are significant in the 

 infectious process is not known, but it would not be surprising to learn 

 that these differences are essential in allowing the phage to synthesize 

 DNA in an alien environment. 



B. GLUCOSYLATION OF^ 5-HVDROXVMETHYLCYTOSINE (HMC) 



The composition of the DNA in T-even bacteriophages i.>^ unicjue in 

 that it contains 5-hydroxymethylcytosine instead of cytosine (Wyatt 

 and Cohen, 1953), and it also contains glucose (Jcsaitis, 1954; Volkin, 

 1954; Sinsheimer, 1954). Flaks and Cohen demonstrated that a new 

 enzyme, deoxycytidylate hydroxymethylase (which accounted^ for the 

 synthesis of this viral pyrimidine; see Section II,C) was induced in the 

 bacteriophage-infccted system. Likewise, Kornberg et al. (1959, 1961; 

 Zimmerman ef a/.. 1962) have indicated that new enzymes capable of 

 glucosylating HMC-containing DNA were formed soon after infectio^i 

 The elegant experiments of Lehman and Pratt (1960) using a highly 

 purified phosphodiesterase wliicli could degrade the normally DNase- 

 resistant bacteriophage DNA to mononucleotides (Lehman, 1960) de- 

 lineated the .'Structures and distribution of the glucosylated HMC- 

 nucleotides isolated from T2, T4, and T6 DNA preparations. A compila- 

 tion of their data is shown in Table XXVIIL If we assume that a specific 

 enzyme is required for each type of glucosylated nucleotide, six enzymes 

 (two for each phage) should be demonstrable. So far, five different 

 enzymes have been purified and characterized (Zimmemian ef al., 1962; 



