From: Rafal Smigrodzki (rafal@smigrodzki.org)
Date: Fri Jun 06 2003 - 22:46:29 MDT
----- Original Message -----
From: "Robert J. Bradbury" <bradbury@aeiveos.com>
To: <extropians@extropy.org>
Sent: Friday, June 06, 2003 7:23 PM
Subject: Re: GENOMES: Human gene number revised down
>
> On Fri, 6 Jun 2003, Michael M. Butler wrote:
>
> > "I am only an egg." By "alternate splicing", do you mean anything like
RNA
> > autoenzymatic activity?
>
> No, I believe there is an explicit "splicosome" to regulate how
> the exons in DNA are explicitly put together. I believe that most of
> this requires proteins (not RNA) to splice the exons. On top of that
> there may either be cell specific or even multiple cell specific machines
> that do the work. (E.g. "I splice this and you splice that...")
### Spliceosomes are complex assemblages of proteins, with an enormous
number of tissue and cell-type specific factors.
>
> These may of course contain some RNA enzymatic activity -- that isn't
clear
> to at least to myself at this point. It would appear there is a lot of
"mix and
> match" with regard to specific exons in specific tissues to generate
specific
> functions. If one has 20,000+ genes generating at least 3 forms
> of proteins in a variety of 300+ different cell types it is going to be a
> nightmare to unravel.
### There are genes with literally hundreds of splice variants, especially
in the CNS. If you add the farnesylation, phosphorylation, oxidation,
ubiquitination, glycosylation, and other forms of post-translational
modification, you end up with literally millions of distinct molecular
species. No worry, we are still a bit more complicated than our desktop
PC's.
Rafal
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