SECTION I. PROTEINES 



L'HISTOCHIMIE DES NUCLÊOPROTEINES: 



LE RÔLE DU NOYAU CELLULAIRE 



DANS LA SYNTHÈSE DES ACIDES NUCLÉIQUES 



ET DES PROTÉINES 



J. BRACHET 



Laboratoire de Morphologie animale 

 Faculté des Sciences de l'Université libre de Bruxelles 



Three différent methods are now available for the study of the biochem- 

 ical rôle of the cell nucleus: 



1) cytochemical methods for the détection of the nucleic acids (DNA, 

 RNA'» and the associated proteins, as well as autoradiography techniques 

 which can follow the incorporation of varions radioactive precursors 

 into the varions cell organelles; 



2) comparison of nucleate and anucleate fragments of unicellular 

 organisms, with quantitative ultra-mi cromethods; 



3) homogenization of tissues, followed by différentiel centrifugation 

 in order to separate the varions cell constituents. The advantages and 

 disadvantages of thèse three main techniques are critically discussed. 



The main results obtained with thèse three methods are presented; 

 the conclusions reached are very similar, if not identical. Hère are 

 thèse conclusions: 



1) the main rôle of the cell nucleus is the synthesis of nucleic acids 

 (both DNA and RNA); 



2) in ail the cases so far studied, the cell nucleus has been found to 

 exert a much doser control on cytoplasmic RNA synthesis than on cyto- 

 plasmic protein synthesis; it is likely that the control of the nucleus on 

 cytoplasmic protein synthesis is an indirect one, mediated through the 

 transfer to the cytoplasm of RNA of nuclear origin; 



3) spécifie proteins can be synthesized in the cytoplasm in the ab- 

 sence of the nucleus, thus in the absence of direct genetic information. 



The fact that entirely différent methods, applied to a wide variety of 

 biological objects, lead to almost identical conclusion increases con- 

 fidence in the now available histochemical techniques for nucleic acid 

 protein détection. 



-61 - 



