RNA AND GROWTH PROTEIN SYNTHESIS 



281 



Thus the investigator is able, 

 with amoebae, to modify almost 

 at will the RNA content by suita- 

 ble treatments with ribonuclease 

 and RNA. What are the conse- 

 quences of these changes in the 

 RNA content on growth and 

 protein metabolism? 



Growth, as we have already 

 seen, is directly related to the 

 RNA content of the amoebae : 

 the organisms which have had 

 their RNA store depleted are 

 unable to divide; after resto- 

 ration of the RNA content, on 

 the addition of external RNA, 

 normal multiplication proceeds. 

 Autoradiography observations 

 on the incorporation of labelled 

 phenylalanine into the proteins 

 of the treated amoebae entirely 

 support this view : as can be seen 

 on Fig. 8, ribonuclease produces 

 a considerable inhibition (about 

 go%) of the incorporation; re- 

 covery of basophilia, on the addi- 

 tion of RNA, is usually followed 

 by a parallel recovery of in- 

 corporation. 



Very similar results have been 

 obtained, in our laboratory, by 

 Ficq and Errera (1955b) on 

 starfish oocytes : treatment with 

 ribonuclease produces a consid- 

 erable drop of basophilia and a 

 parallel inhibition of the incor- 

 poration of labelled phenylala- 

 nine, especially in the RNA-rich 

 nucleolus and cytoplasm. How- 

 ever, in the starfish oocytes, the 

 RNA-RNase complex breaks 

 down if the treated cells are 

 simply washed and left in normal 

 sea-water: simultaneously, the 

 incorporation of the labelled 

 amino acids returns to normal. 



Literature p. sgg 





7a 





7b 





. O. 



7c 



Fig. 7. a: control amoeba; b: ribonuclease treated 

 amoeba (i h., o.i mg/ml) ; c: recovery of the ribonu- 

 clease treated amoebae upon addition of RNA (Unna) . 



