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Francis Crick defined the so-called Central Dogma of molecular biology namely,
DNA encodes RNA, encodes protein.
The process by which RNA is made from a DNA template is called transcription,
whereas decoding of the RNA,
specifically messenger RNA, to make protein is referred to as translation.
In this talk, I focus on basic aspects of transcription,
specifically transcription of eukaryotic class II genes,
those transcribed by RNA polymerase II.
To put this into context,
I want to remind you that transcription in
eukaryotic cells is catalyzed by three distinct RNA polymerases;
Pol l, Pol II, and Pol III.
Pol I is dedicated to the synthesis of ribosomal RNA,
except the smallest of them, 5S ribosomal RNA.
Pol II transcribes protein and coding genes to yield
messenger RNA as well as a few small nuclear RNAs,
and Pol III synthesizes transfer RNAs, 5S ribosomal RNA,
and also a few small nuclear RNAs,
whereas only messenger RNA is translated to yield protein.
The ribosomal and transfer RNAs are also
directly involved in protein synthesis by the ribosome.
In 2001, the complete DNA sequence of the human genome was published,
revealing approximately 30,000 protein encoding genes.
This was an extraordinary achievement,
but like so many scientific milestones,
raised as many questions as were answered.
Notable are the questions of how these 30,000
genes are expressed to affect cell growth and differentiation,
and how expression of these genes is regulated.
This talk addresses several fundamental questions regarding Pol II transcription.
First, how does Pol II identify a gene?
What are the cis-acting DNA sequences and what are
the transacting proteins that are required for transcription?
Second, how does Pol II initiate transcription?
How do the proteins that are required for initiation
interact with Pol II to promote messenger RNA synthesis?
Third, how is transcription regulated in response to factors that affect gene expression?
Including the physiological and developmental factors to which all cells respond.
I'll revisit these questions as I proceed.
I've organized my presentation of the Pol II machinery into five parts.