TABLE I 

 Chemical Composition of Chromatin (mass ratios) 



Calf "niynius Calf Endometrium Rat Liver Pea Embryo Ascites TXimor 



of RNA is seen to be sensitive to actinomycin D. 

 It is reduced in the presence of DNase but as the 

 chromatin is fairly resistant to DNase the effect 

 is more striking following pre-incubation of the 

 chromatin with DNase. 



Now, we know there are histones associated 

 with this template, and it was intriguing to see if 

 an appreciable quantity of histone could be re- 

 moved without dissociating too much of the non- 

 histone proteins that were present. So Dr. 

 Marushiga examined salt extraction of rat liver 

 chromatin and I show the results of some of 

 these experiments in Fig. 4. He extracted with 

 sodium perchlorate. First of all, as the concen- 

 tration of sodium perchlorate increases, his- 

 tones are released. Then in the region at about 

 0.4 M he began to dissociate a sizeable amount 

 of non-histone protein. If one looks at salt con- 

 centrations where there is not a great deal of 

 non-histone protein removed, but a considerable 

 amount of histone is removed, it is possible to 

 see in all three of these cases that RNA syn- 

 thesis in the in vitro experiments has been con- 

 siderably elevated. There appears to be a posi- 

 tive correlation between histone removed and 

 increase in RNA synthesis. 



Does the RNA made in these in vitro sys- 

 tems have any biological significance? Can it 

 direct protein synthesis? In Table HI you see 

 the results of some work done by Dr. Bonner 

 and Dr. Huang. They isolated chromatin from 

 two sources: the pea cotyledon and from pea 

 apical buds. They used the chromatin to gene- 

 rate RNA and then coupled it withafull protein- 

 synthesizing system. Then, after incubation, they 

 used immunological precipitation techniques to 

 detect the formation of globulins. In the case of 

 cotyledons which make globulin in vivo, the 

 chromatin is able to direct (via RNA synthesis) 



TABLE II 



Inhibition of the RNA Synthesis Directed by Rat Liver 

 Chromatin 



^Chromatin was preincubated with DNAase at 37" C for 10 nnin. 



(Table 3, Marushiga and Bonner, /. Mol. Biol. 15, 160, 

 1966; reproduced with permission of Academic Press.) 



a reasonable percentage of globulin syn- 

 thesis. However, the apical bud chromatin, when 

 treated in identical circumstances, appears to 

 be able to synthesize only a very small amount. 

 They ran some parallel experiments with T4 

 phage (which so far as we know do not make pea 

 seed globulin) and the cross reaction they ob- 

 tained would suggest a low background effect 

 comparable to that obtained from apical bud 

 chromatin. Apical buds in vivo do not make pea 

 seed globulin. Thus there is a correlation be- 

 tween the protein made by a specific tissue and 

 the ability of chromatin derived from that tissue 

 to make messenger for that protein. 



PAPACONSTANTINOU: Why is there that 

 variability in the amount of protein that is being 

 synthesized in the first column? You have about 



133 



