GROSS: It imposes an analytical require- 

 ment on the model. If you' re going to have recog- 

 nition, then you have to have sufficient length of 

 RNA to recognize the gene or the cistron. 



CHALKLEY: How big is an operator gene? 



GROSS: Well, it's a fraction or a few per 

 cent of an operon. However, what I'm suggesting 

 is that isolated chromatin ought to have a lot of 

 RNA, 



CHALKLEY: It has some RNA. When you 

 isolate chromatin and nucleohistone it has not 

 got a great deal of RNA; nonetheless a residual 

 quantity of RNA is always found. This RNA is 

 very difficult to remove. It's resistant to RNase, 

 unless you pre-treat it with DNase or unless you 

 heat it to 60°. 



KAHN: I'm curious. Where do you postulate 

 that the RNA for the functional repressors is 

 synthesized? It seems to me that the most likely 

 spot would be the very same portion of the DNA 

 template that it will later repress. 



CHALKLEY: I think that is, in fact, very 

 reasonable. 



PERSON: Are you going to have repression 

 by the RNA or by the protein? 



CHALKLEY: I imagine it's the protein 

 that's involved in the repression. So far it has 

 been shown in our group that you can put cationic 

 polypeptides on the template and get a repres- 

 sion of the DNA-dependent RNA synthesis. It's 

 a fact you can work on anyhow. 



TS'O: I would like to make a statement about 

 this. The most difficult problem in setting up the 

 hypothesis for histone or any proteins to be the 

 genetic repressor is that we know nothing about 

 how the proteins and the nucleic acids interact 

 specifically. How do proteins recognize the base 

 sequences or the base composition of the nucleic 

 acids? The present status of our biochemical 

 knowledge does not give any model in molecular 

 terms which would lead to this kind of specificity. 

 For instance, in protein synthesis, even though 

 the transfer RNA can form base pairs with the 

 messenger RNA, the translation of the genetic 

 codes is dependent upon the recognition process 

 between the transfer RNA and the amino acid 

 activating enzyme. What you are trying to do 

 here is almost the same thing, because you are 

 trying to use the RNA to recognize the DNA 

 through the accepted based pairing mechanism. 

 However, specific base proteins have to be able 

 to recognize and be attached to the specific RNA. 



CHALKLEY: Now you're putting a require- 

 ment in which I don't think is necessary. All we 

 have to say is that there has to be an enzyme 

 or enzymes to link those two and this enzyme 



has to be able to recognize the basic protein. 

 Now, surely one protein can recognize another 

 protein? 



POLLARD: I feel you're missing one very 

 important question. I think your model is very 

 good, but there has to be something that really 

 rips the RNA off. It can't just come off; it has 

 to be torn off. Now, if you were to take just 

 the soluble RNA and quietly put histone on the 

 end of the RNA, you would block the tear-off 

 mechanism. The rate at which that stuff comes 

 off is impressive. It's linked in complementary 

 links of base pairing. Nevertheless, it comes 

 off. No one has been able to observe the time it 

 takes. 



CHALKLEY: That's true. 



POLLARD: Also, if you were going to have 

 as small a section of the DNA in the bacterial 

 cell as you indicated, then the length of the RNA 

 being torn off must be 1 5 times as long. 



CHALKLEY: Yes, this was an arbitrary 

 length for purposes of discussion. 



POLLARD: I suspect you may be on the 

 right track with this, but the RNA just doesn't 

 do anything you like. 



MAURER: It should be pointed out that this 

 is a kind of equilibrium and therefore it is sen- 

 sitive to all kinds of factors which influence 

 this equilibrium. If one enhances the degrada- 

 tion, for example, it would certainly have an 

 effect on it, probably by shifting the rate of 

 reactions. Furthermore, I would like to stress, 

 in respect to the hormone studies so far done, 

 that it isn't yet completely clear whether there 

 is an RNA polymerase increase due to new 

 formation of the RNA polymerase or to an acti- 

 vation of the enzyme as far as RNA template 

 synthesis is concerned. However, in these ex- 

 periments which Dr. Chalkley has presented, 

 it was shown that there is an increase in tem- 

 plate activity since we put in high excess of 

 RNA polymerase. This is the main point. It 

 really looks like the hormones are, by some 

 means, removing some kind of repressor and 

 not just increasing the RNA polymerase. We 

 suggest that hormones inhibit the formation of 

 some functional repressor and in this way alter 

 the dynamics. 



PERSON: Wouldn't you than want them con- 

 nected to the things that are being permanently 

 repressed in the model, so that they could open 

 up new regions? 



CHALKLEY: Well, if you do that, you have 

 to specifically involve proteins other than his- 

 tones in this sort of specific permanent gene 

 repression and this may be quite possible. There 



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