Problems in Polynucleotide Biosynthesis 



J. N, Davidson 



Department of Biochemistry, University of 

 Glasgow, Scotland 



One of the most exciting recent developments in biochemistry has been 

 the now classical work on the biosynthesis of deoxyribonucleic acid (DNA)* 

 by Romberg and his colleagues (for summary see ref. [i]) who showed that 

 extracts of Eschericliia coli contain kinases which bring about the phos- 

 phorylation of deoxribonucleotides to the triphosphate stage and a poly- 

 merase which acts on the triphosphates in the presence of a suitable DNA 

 primer with the production of deoxyribopolynucleotide macromolecules 

 built to the design of the primer molecule. 



Such enzymes are also present in mammalian tissues. They have been 

 the subject of extensive investigations by Potter and his colleagues in 

 Wisconsin [2, 3, 4] and Canellakis in Yale [5, 6, 7] using regenerating rat 

 liver, and by our own group in Glasgow [8, 9, 10, 11, 12, 13, 14, 15] using 

 extracts of Ehrlich ascites carcinoma cells. Similar systems are present in 

 calf thymus [16] and mouse leukaemic cells [17]. The following account is 

 based largely on the work of a group of investigators including Dr. R. M. S. 

 Smellie, Dr. H. M. Keir, Dr. E. D. Gray, Dr. S. M. Weissman, Dr. J. 

 Richards, Dr. J. Paul and Mr. D. Bell. 



The process of DNA biosynthesis can be divided into three separate 

 stages : 



(i) The biosvnthesis of the purine and pyrimidine nucleotides and 



their conversion to the deoxyribonucleoside monophosphates, 

 (ii) The phosphorvlation of the deoxyribonucleoside monophosphates 

 to the corresponding triphosphates by appropriate kinases. 



* The following abbreviations are used in this paper : DNA for deoxyribonucleic 

 acid; dAMP, dGMP, dCMP, dUMP, UMP, OMP, IMP, and TMP for the 

 s'-monophosphates of deoxyadenosine, deoxyguanosine, deoxycytidine, deoxyuri- 

 dine, uridine, orotidine, inosine and thymidine respectively; dATP, dADP, 

 dGTP, dGDP, dCTP, dCDP, TTP and TDP for the s'-tri- and diphosphates 

 respectively of deoxyadenosine, deoxyguanosine, deoxycytidine and thymidine ; 

 TdR for thymidine ; ATP for adenosine-5 '-triphosphate ; DPN for diphosphopyri- 

 dine nucleotide; tris for 2-amino-2-hydroxymethyl propane- 1 : 3-diol; TdR kinase, 

 TMP kinase and TDP kinase denote respectively the enzyme systems responsible 

 for the formation of TMP, TDP and TTP. 



