SECTION 4 



GENE ACTION 



4.1. Studies on the Function of Histones and Similar 

 Basic Proteins. I. Leslie (Belfast, Great Britain. 



Chemical similarities have recently been de- 

 tected between the histones associated with 

 DNA and the basic proteins associated with 

 RNA in ribosomes. However, the function of 

 this class of protein is not yet known. From their 

 chemical and physico-chemical investigations, 

 Stedman and his collaborators have proposed 

 that histones act as gene-regulators. 



Latent-nuclease activity in ribosomes is known 

 to be associated with basic proteins or proteins 

 having compositional similarities to histones. 

 The hypothesis that "histone-nucleases" control 

 gene-expression in metazoan cells (Leslie, 1961) 

 is being investigated with the aid of biochemical 

 and tissue culture techniques. 



Fractionation on carboxymethylcellulose and 

 electrophoresis on starch-gel has been applied to 

 the basic proteins of nuclei and ribosomes. With 

 two procedures for detecting nuclease activity, it 

 has been found that ribosomal RNA is most 

 readily degraded by proteins of the lysine-rich 

 type. Degradation by the arginine-rich protein is 

 negligible. 



Pulse-labelling and chase experiments with a 

 human cell strain (HLM) are being used to 

 follow the synthesis of the different types of 

 RNA and basic proteins, when the cultures are 

 treated with either fluorodeoxyuridine, which 

 selectively inhibits DNA formation, and actino- 

 mycin C, which partially inhibits RNA forma- 

 tion. The results will be described. 



phage and superinfecting phage respectively. The 

 prophage is not induced, the few prophage 

 markers found in the progeny are rescued by 

 recombination. The same appears to be true 

 when a "virulent" A is used as the superinfecting 

 phage. In superinfection of cells lysogenic for A 

 with another A and 434 hy, the superinfecting A 

 is not multiplied: the recovery of the corres- 

 ponding type in the progeny is below the multi- 

 plicity of infection. These particles derive their 

 protein coat from the unrepressed 434 functions. 

 These results suggest either that the control of 

 replication does not entirely depend on the re- 

 pression of synthesis of "'early proteins", or that 

 the functions involved in replication are not 

 interchangeable between A and 434 hy. If this is 

 the case, the genetic loci for these functions 

 should map in a small region which includes 

 cistron ci (Kaiser and Jacob, 1957) but does not 

 extend as far to the left as the site of the defective 

 mutation d22 (since healthy A can be rescued 

 from A d-22 by recombination with 434 hy). 



1. Kaiser, A. D. and Jacob, F. Virology, 4, 



509, 1957. 



This research has been supported by Euratom- 

 U.L.B.-contract 016-61-10 ABIB, by the Air 

 Force Office of Scientific Research, OAR 

 62-17 (through the European Office Aerospace 

 Research, United States Air Force) and by 

 the Belgian Fonds National de la Recherche 

 Scientifique. 



4.2. Data on the Control of Genetic Replication in 

 Temperate Bacteriophages. R. Thomas (Brus- 

 sels, Belgium). 



When a lysogenic bacterium is superinfected 

 with a temperate bacteriophage which is closely 

 related to the prophage but has a different pat- 

 tern of immunity, the superinfecting phage 

 multiplies normally. The question can be asked 

 whether functions supplied by the superinfecting 

 phage will induce the prophage. 



Suitably marked derivatives of A and 434 hy 

 (Kaiser and Jacob, 1957) (1) were used as pro- 



4.3. Regulatory Function of Sorbose on Sugar Meta- 

 bolism in Neurospora. Walter Klingmuller 

 (Berlin, Germany). 



Growth of Neurospora on filter sterilized su- 

 crose medium is blocked by sorbose. (1) By 

 treatment with nitrous acid mutants have been 

 produced that are not blocked. These mutants 

 also grow on fructose/sorbose and on sorbose 

 alone, the wild type does not. Growth on those 

 media is in dense, small colonies, the growth rate 

 somewhat retarded as compared to other media. 



Growth on sorbose alone may be due to im- 

 purities in this sugar. Growth on fructose/sorbose 



37 



