My name's Mark Timmers.
I've been interested in the process of gene regulation
for a very long time, and in doing so,
we've gathered a number of insights.
I'm going to share with you what we've learned
about the basal transcription by RNA polymerase ii.
But before we go into the details
of the basal transcription process
itself, it's important to
review the elements which
are controlling the process of transcription.
These are typically, as indicated in orange here,
the enhancer sequences which
can be located either upstream
or downstream or even in the gene,
a locus control region which can act
over larger distances, and the
function of these DNA elements
fits into the events that are happening
at the start site, indicated by the arrow.
And the start site is part of
the core promotor sequence,
which is surrounding the start site.
And it's about only 50 base
pairs in total sequence.
Although we know that these elements
are important from the simple act
of looking at the DNA
sequences, it's very difficult
to find these functional elements.
These DNA elements function
by attracting proteins.
From the DNA sequence of a number of genes,
we can now determine the number of genes which
are involved in expression of the genome.
For a simple eukaryote like yeast,
which has about 6,000 genes,
there's about 170 gene-specific transcription factors
which bind to upstream sequences like enhancers.
There's about 250 or so chromatin
remodeling and modifying factors.
And if we focus on the basal machinery,
there's about 60 to 70 general
transcription machinery proteins.
In addition to this, yeast has about 20 elongation proteins
and there's a number of upstream
regulatory factors like kinases,
ubiquitin, rare proteins, mRNA splicing proteins, export proteins.
I'm not going to talk about those.
So the total set is about 60 proteins
which are involved in basal machinery.
If you now look at the more
complex eukaryotes like ourselves,
we have about 20,000
messenger RNA coding genes.
There's a number of micro RNAs, and it's
about 5,000 to 10,000 long non-coding RNAs.
So in total, that's about
30,000 to 35,000 different RNAs
which are produced by RNA polymerase.
If you now look at the number
of regulatory proteins,
you see an expansion of the number
of gene-specific transcription
factors, of chromatin proteins,
but the basal machinery is still
comprised of about 75, in this case,
general transcription machinery
The elongation protein family has
expanded, but what's also important
is that the general
machinery of yeast or human
is quite similar in its
makeup and the number
of genes that are involved.