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Printable Handouts
Navigable Slide Index
- Introduction
- Heterochromatin
- Types of heterochromatin
- Heterochromatin varies in different cell types
- Barr body heterochromatin in a female nucleus
- white gene expression results in a red eye
- Chromosome inversion displaces the white gene
- Euchromatic region silenced by heterochromatin
- HP1 affects heterochromatin silencing
- HP1 in heterochromatin and euchromatic sites
- Su(var)3-9 mutations suppress silencing
- HP1 invades PEV-inactivated euchromatic regions
- Heterochromatin silencing at the molecular level
- Heterochromatization - effects on methylation
- DNA accessibility to methylase in vivo
- Gene silencing by heterochromatin occlusion
- Nucleosomes are ordered in heterochromatin
- HP1 loss causes silencing of the light gene
- HP1-dependent heterochromatin gene expression
- SU(VAR)3-9-HP1-nucleosome interaction
- HP1 & H3K9me3 methyl mark do not co-localize
- Histone methylation is reversible
- Transcription results in chromatin demethylation
- Phosphorylation at H3S10 evicts HP2
- Epigenetics
- Active vs. epigenetically silenced chromatin
- Epigenetic stability through mitosis
- SU(VAR)3-9 and epigenetic memory
- Transgene reporter for heterochromatin silencing
- Promoter strength and heterochromatin silencing
- Heterochromatin silencing upon differentiation
- Silencing in differentiating & undifferentiated cells
- Loss of HP1 results in telomere fusions
- Telomere elongation in heterozygous HP1 mutants
- Het-A telomeric retro element transcription & HP2
- RNAi and the targeting of heterochromatin
- HP1 binds telomeres regardless of sequence
- Meiotically heritable RNAi-mediated silencing (1)
- Meiotically heritable RNAi-mediated silencing (2)
- Acknowledgments
Topics Covered
- Heterochromatin as a cytological phenomenon
- Heterochromatin and gene silencing
- Heterochromatin and DNA accessibility
- Histone modification and control of heterochromatin assembly
- Stability of epigenetic silencing by heterochromatin during development
- Heterochromatin and telomere stability
Links
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Talk Citation
Eissenberg, J.C. (2014, February 4). Heterochromatin, epigenetics and gene expression [Video file]. In The Biomedical & Life Sciences Collection, Henry Stewart Talks. Retrieved December 8, 2024, from https://doi.org/10.69645/GMPK7246.Export Citation (RIS)
Publication History
Financial Disclosures
- Prof. Joel C. Eissenberg has not informed HSTalks of any commercial/financial relationship that it is appropriate to disclose.
A selection of talks on Genetics & Epigenetics
Transcript
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0:00
The title of this talk
is Heterochromatin,
Epigenetics and Gene Expression.
I'm Joel Eissenberg.
I'm a professor in the
Department of Biochemistry
and Molecular Biology at Saint
Louis University School of Medicine.
My goal in this talk is to
survey our understanding
of heterochromatin
and its connection
to the idea of epigenetic
control of gene expression.
Terms like heterochromatin
and epigenetics
are frequently used to
disguise, rather than explicate,
our understanding of
how cells organize
and use genetic information.
In this presentation,
I'll define these terms
and discuss epigenetics in
the context of heterochromatin
and the evidence that it can
influence gene expression.
0:47
The term heterochromatin
was coined by Emil Heitz
to refer to the material in the
eukaryotic nucleus that fails
to decondense after
telophase in the cell cycle.
On the left in this slide is an
image showing the chromosomes
of a cell at or near telophase
stained with a fluorescent dye
that labels DNA.
The bright fluorescent staining, is
coextensive with the chromosomes.
In contrast, the interphase nucleus
on the right is filled with DNA,
but only certain regions stain
brightly, the heterochromatin.
The condensed state
of heterochromatin
concentrates the DNA, making these
regions stand out on the background
of the rest of the DNA
fluorescents in the nucleus.
This property distinguishes
it from the remaining
so-called euchromatin, or
true chromatin, that undergoes
cyclic condensation
and decondensation.
In contrast, heterochromatin
exhibits heterocyclic behavior,
hence the term heterochromatin.
Thus, the term
heterochromatin was originally
coined to describe a
cytological phenomenon, not
a genetic or biochemical phenomenon.
Heitz ultimately showed that most
or all eukaryotic chromosomes
are differentiated
along their lengths
by zones of euchromatin, which he
recognized as relatively gene rich,
and heterochromatin, which he
recognized as relatively gene poor.
More recently, the
term heterochromatin
has been used more promiscuously
to describe any form of chromatin
associated with
transcriptional silencing
and/or chromatin enriched for
certain biochemical markers,
such as cytosine methylation, or
certain histone modifications.
In this presentation, I'll
stick to examples that
are consistent with the
original definition of the word.