31. SYNTHESIS OF POLYNUCLEOTIDES 11") 



nucleotides 24 ' 26 can serve as primers for the calf thymus polymerase. 10781 

 These initial observations offer the promise that further insight into the 

 mode of action of the polymerases will be forthcoming in the near future 

 from studies using different types of synthetic oligonucleotides of known 

 structures. 



2. Mammalian Systems 



a. Rat Liver 



Bollum and Potter 108 demonstrated the incorporation of tritiated thymi- 

 dine into DNA in homogenates from regenerating rat liver. The multien- 

 zyrae system responsible for the incorporation was found to be present in 

 the soluble high-speed supernatant fraction. Some further properties of 

 the system were reported by these authors as well as by Mantsavinos and 

 Canellakis. 109 In regenerating rat liver the appearance of the enzyme sys- 

 tem (after about 18 hours regeneration period) was correlated with the 

 appearance of DNA synthesis in vivo. 110 The requirements of the system 

 were established to be 108, 109 the presence of DNA, an energy source, and 

 the incorporation was stimulated by the complementary deoxyribonucleo- 

 side-5 '-phosphates and inhibited by pyrophosphate. By partial purification 

 of the polymerizing enzyme in the supernatant fraction, Bollum 111 has 

 demonstrated more clearly the requirements for Mg ++ , DNA, and the 

 presence of all four deoxyribonucleoside-5 '-triphosphates, for maximal in- 

 corporation of tritium labeled thymidine-5'-triphosphate. In all these prop- 

 erties, therefore, the rat liver enzyme is similar to the bacterial system de- 

 scribed above. 



b. Thymus 



The incorporation of C 14 -thymidine into DNA by rabbit thymus nuclei 

 was reported by Friedkin and Wood. 112 The presence of the polymerase 

 type of activity has been shown in thymus by Harford and Romberg 113 

 and by Bollum. 114 The requirements of this polymerase 115 are, again, the 

 four deoxyribonucleoside triphosphates, DNA and Mg ++ and Bollum 116 has 



107a F. J. Bollum, Federation Proc. 19, 305 (1960). 



108 F. J. Bollum and V. R. Potter, J. Am. Chem. Soc. 79, 3603 (1957); /. Biol. Chem. 

 233, 478 (1958). 



109 R. Mantsavinos and E. S. Canellakis, J. Biol. Chem. 234, 628 (1959). 



110 F. J. Bollum and V. R. Potter, Cancer Research 19, 561 (1959). 



111 F. J. Bollum, J. Am. Chem. Soc. 80, 1766 (1958). 



112 M. Friedkin and H. Wood, J. Biol. Chem. 220, 639 (1956). 



113 C. G. Harford and A. Romberg, Federation Proc. 17, 515 (1958). 



114 F. J. Bollum, Federation Proc. 17, 193 (1958). 



116 F. J. Bollum, Ann. N. Y. Acad. Sci. 81, 792 (1959). 



