PROBLEMS IN POLYNUCLEOTIDE BIOSYNTHESIS lOI 



tendency to vary with the state of proliferation of the tissue and in its 

 susceptibiUty to the action of the interfering factors present in extracts of 

 normal resting liver. It must therefore exercise a profound effect in the 

 regulation of DXA biosynthesis. Such a conclusion would be in agreement 

 with the well-known views of Potter [20, 21]. 



The overall picture of DNA formation is illustrated in Fig. 3. In 

 addition to feedback mechanisms controlling nucleotide biosynthesis 

 [20, 21] at least two main mechanisms seem to control polynucleotide 

 formation. One is the conversion of cytidylate to deoxycytidylate which 

 appears from the recent work ot Reichard, Canellakis and Canellakis [22] 

 to occur at the diphosphate level and to be controlled by the triphosphate 

 level in the cell; the second is the system involved in the formation of 

 TTP from TMP. It may well be that a third method of control lies in the 

 presence in certain tissues of inhibitors for the polymerase. 



References 



1. Kornberg, A., Science 131, 1503 (i960). 



2. Bollum, F. J., and Potter \'. R. J. biol. Chem. 233, 478 (1958). 



3. Bollum, F. J., and Potter, V. R., Cancer Res. 19, 561 (1959). 



4. Bollum, F. J., Anderegg, J. \V., McElya, A. B., and Potter, \\ R., Cancer Res. 

 20, 138 (i960). 



5. Canellakis, E. S., and Mantsavinos, R., Biochim. biophys. Acta 27, 643 (1958) 



6. Mantsavinos, R., and Canellakis, E. S.,^. biol. Chem. 234, 628 (1959). 



7. Canellakis, E. S., Jaffe, J. J., Mantsavinos, R., and Krakow, J. S., J. biol. 

 Chem. 234, 2096 (1959)- 



8. Smellie, R. M. S., Keir, H. M., and Davidson, J. N., Biochim. biophys. Acta 



35» 389 (1959)- 



9. Keir, H. M., and Smellie, R. M. S., Biochim. biophys. Acta 35, 405 (1959). 



10. Smellie, R. M. S., Gray, E. D., Keir, H. M., Richards, J., Bell, D., and 

 Davidson, J. N., Biochim. biophys. Acta 37, 243 (i960). 



11. Weissman, S. M., Paul, J., Thomson, R. Y., Smellie, R. M. S., and Davidson, 

 J. X., Biochem.y. 76, iP (i960). 



12. Weissman, S. AI., Gray, E. D., Thomson, R. Y., Smellie, R. M. S., and 

 Davidson, J. N., Biochem. J. 76, 26P (i960). 



13. Weissman, S. M., Smellie, R. M. S., and Paul, J. (i960), Biochim. biophys. 

 Acta 45, loi. 



14. Gray, E. D., Weissman, S. M., Richards, J., Bell, D., Keir, H. M., Smellie, 

 R. M. S., and Davidson, J. N. (i960), Biochim. biophys. Acta 45, iii. 



15. Weissman, S. M., et al. (unpublished results). 



16. Bollum, F. J., Fed. Proc. 18, 194 (1959). 



17. Mantsavinos, R., and Canellakis, E. S., Cancer Res. 19, 1239 (1959). 



18. Lima-de-Faria, A., Hereditas, Lund. 45, 632 (1959). 



19. Hiatt, H. H., and Bojarski, T. B., Biochem. biophys. Res. Comm. 2, 35 (i960). 



20. Potter, V. R. Univ. Mich. med. Bidl. 23, 401 (1957). 



21. Potter, V. R., and Auerbach, V. H., Lab. Investigation 8, 495 (1959). 



22. Reichard, P., Canellakis, Z. N., and Canellakis, E. S., Biochim. biophys. Acta 

 41, 558 (i960). 



