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From: diaz@aecom.UUCP
Newsgroups: sci.bio
Subject: Re: question - DNA's information
Message-ID: <1000@aecom.UUCP>
Date: Thu, 2-Apr-87 23:51:40 EST
Article-I.D.: aecom.1000
Posted: Thu Apr  2 23:51:40 1987
Date-Received: Sun, 5-Apr-87 10:02:32 EST
References: <11189@teknowledge-vaxc.ARPA> <978@aecom.UUCP> <3310@udenva.UUCP> <1534@husc6.UUCP>
Organization: Graduate School of Hard Knocks
Lines: 35
Summary: Not many catalytic RNAs at all

In article <1534@husc6.UUCP>, cherry@husc4.HARVARD.EDU (michael cherry) writes:
> 
> The unit of information stored in the chromosomes is the nucleotide. Not
> all of that information ever makes it to proteins. Much of the information
> in DNA never even makes it to RNA. Also there are many RNAs which either
> have a structural or catalytic function encoded in the DNA. Thus the 
> information is at the DNA level. 

Although I hate to pick at others' articles, I have seen the increasing
use of the term "catalytic RNAs" to describe those RNA molecules (e.g.
the Tetrahymena rRNA) which mediate their own splicing in vitro. This
bastardization of the term catalysis has unfortunately infiltrated many
of our scientific journals.

Let's make it clear that self-splicing RNAs mediate their splicing via
intramolecular reactions. Once exons are spliced together, the reaction
is over. By definition, a catalyst accelerates the rate of a chemical
reaction without itself being consumed in the net reaction.
Self-splicing RNAs are NOT catalytic. 

The only examples I know of genuinely catalytic RNAs are: M1 RNA from
E.coli, which has been elegantly shown by Sidney Altman & coworkers to
accurately process the 5' termini of tRNAs in the absence of its
physiological protein cofactor in vitro; M1 RNA-like molecules from
Bacillus subtilis and other organisms; the Tetrahymena rRNA intron left
over from the self-splicing of this transcript, which has been shown by
T. Cech, et al, to possess RNA polymerase- and RNA restriction
endonuclease-like activities in vitro. There may be other examples of
which I may not be aware (if so, let me know). Let's be careful in our
description of the members of the RNA world. 

-- 
            dn/dx = Dan Diaz    (philabs!aecom!diaz)
            Department of Molecular Biology & Pizza Chemistry AECOM
            "Hold the E.coli"