Chromatin Architecture and the Regulation of
Gene Expression prepared and presented by Jeffrey Hansen,
Professor of Biochemistry and Molecular Biology, Colorado State University.
Hello and welcome to
the presentation on Chromatin Architecture and the Control of Gene Expression.
This talk is organized into six sections.
I begin with a brief overview of Chromatin Architecture and
its relevance to Gene Expression in Eukaryotic organisms.
I then, describe in more detail the many different levels of
chromatin organization found in interphase chromosomes.
As a transition into Gene Expression,
I highlight three Milestone Experiments,
each of which established that transcription in
Eukaryotes is fundamentally dependent on chromatin structure.
This is followed by a large section that focuses on
the Regulation of Gene Expression through Alteration of Chromatin Architecture.
I end by emphasizing the dynamic nature of the genome in vivo,
and by highlighting important future questions in this area.
My overall objective is to further your understanding of chromatin structure,
and its many roles in determining how Eukaryotic genomes are organized and deciphered.
An overview of Chromatin Architecture and Gene Expression.
The Multiple Levels of Chromatin Architecture present in
interphase chromosomes are illustrated schematically on this slide.
At the initial level, chromosomal DNA is wrapped
around in octamer of core histones to form the nucleosome.
The nucleosome is the sub-unit of chromatin.
Nucleosome spaced at roughly 200 base pair intervals
along the chromosomal DNA are called Nucleosomal arrays.
Nucleosomal arrays complexed with a specific set of
functional or structural non-histone proteins are called Chromatin fibers.
Chromatin fibers are very dynamic.
They can exist in a number of different folded conformations.
Chromatin fibers are subsequently
twisted, looped and coiled to form the 400 nanometer diameter
extensively condensed chromatids present in the interphase nucleus.