Nuclear control of enzymatic activities 



looks as if enucleation leads to a decrease in phosphorylation reactions, perhaps 

 owing to the lack of some essential co-factors normally produced by the nucleus. 

 These early biochemical abnormalities are quickly followed by a fall in the RNA 

 content, obviously representing the alteration or the loss of some of the microsomes. 

 The importance of the latter, and of the integrity of their RNA for protein synthesis, 

 is now an established fact (Stern and Mirsky, 1952; Gale and Folkes, 1953); it is 

 therefore not surprising to find a fall in the capacity of the enucleated cell for protein 

 synthesis just at the time when the microsomes are injured. On the other hand, the 

 activity of the mitochondria in cell respiration, and presumably of the chloroplasts in 

 photosynthesis, is much less dependent on the presence of the nucleus. 



Such a picture is still little more than a working hypothesis, and it is obvious that 

 much more experimental work will be required before it can be taken as substan- 

 tiated; but it is worth noting that, in a recent review on biochemical genetics, 

 Bonner (1952) concludes that enzymatic synthesis occurs not in the genes themselves 

 but in 'organized cytoplasmic particles'. Since microsomes are much more dependent 

 than mitochondria on the presence of the nucleus, since they are rich in RNA and 

 since they strongly incorporate amino-acids in their proteins it is likely that Bonner's 

 cytoplasmic particles are nothing else but microsomes. It is a gratifying observation 

 that cytochemistry, biochemistry and genetics, starting from very different view- 

 points, all point in the same direction. 



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Balbiani, E. G. (1889). Recherches experimentales sur la merotomie des Infusoires 



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 Ballentine, R. (1939). The intra-cellular distribution of reducing systems in the 



Arbacia egg. Biol. Bull. Woods Hole, 77, 328. 

 Barnum, C. P. and Huseby, R. A. (1950). The intracellular heterogeneity of pentose 



nucleic acid as evidenced by the incorporation of radiophosphorus. Arch. Biochem. 



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 Barth, L. G. and Jaeger, L. (1947). Phosphorylation in the frog's egg. Physiol. 



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 Beth, K. (1953). Experimentelle Untersuchungen liber die Wirkung des Lichtes 



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