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From: werner@aecom.UUCP (Craig Werner)
Newsgroups: net.med
Subject: Re: Re: attacking viruses
Message-ID: <1862@aecom.UUCP>
Date: Mon, 19-Aug-85 23:21:49 EDT
Article-I.D.: aecom.1862
Posted: Mon Aug 19 23:21:49 1985
Date-Received: Wed, 21-Aug-85 07:06:03 EDT
References: <2617@amdcad.UUCP> <404@phri.UUCP>
Organization: Albert Einstein Coll. of Med., NY
Lines: 31

> Phil Ngai  says:
> > in recombinant DNA research they use agents (a form of RNA?) which cut the
> > genes at precise points. [...]  Could we simply employ the right agents to
> > cut up the genes in nasty viruses? [...] The cutting agents seem to be
> > programmed to cut at precise places, which means they should be able to
> > attack the desired virus and nothing else.
> 
> 						Craig, care to take this one?  
> 	Roy Smith 

	Actually I already mailed a response, but with a lead-in like that, I
couldn't turn it down.
	Restriction Enzymes, as described above, generally cut at pre-defined
sequences of usually 6 DNA bases, usually palinodromic (2-fold symetrical).
However, since DNA has only four bases total, the odds of coming up with a
recognition site just by random chance occurs about once every gene or two,
so there is no way to make them specific for viral sequences. (The bacteria
they come from skirt this problem by modifying their own DNA, so only newly
introduced foreign DNA is snipped. Human cells don't do this.)
	Besides, the restriction enzymes are proteins (not RNA, as Phil 
guessed), and proteins cannot get into cells. Protein Hormones get around
this by using receptors, but human cells cannot be expected to have receptors
for bacterial proteins.
	Hence, they would never get to the viral DNA, and even if they did,
they would cut too much of the cellular DNA in the process.
	As Phil said in his response to me, "Oh, well, it was a good idea..."

-- 
				Craig Werner
				!philabs!aecom!werner
		"The world is just a straight man for you sometimes"