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Printable Handouts
Navigable Slide Index
- Introduction
- Chromatin
- Compaction
- The nucleosome
- A source of information
- Chromatin dynamics
- Factors involved in chromatin organization
- The challenge of chromatin assembly
- Chromatin assembly during DNA replication
- Access-repair-restore model
- General steps in chromatin assembly
- Nucleosome assembly
- How to identify histone chaperones?
- Histone chaperones in assembly line
- Histone chaperones as a team
- CAF-1: a nucleosome assembly factor
- CAF-1 role is coupled to DNA synthesis
- Detection of CAF-1 at UV damaged sites
- Other nucleosome assembly factor(s)?
- Nucleosome assembly: Distinct pathways
- H3.3 variant in Drosophila
- Histone H3 variants in mammals
- Amino acid sequences of H3.1, H3.2 and H3.3
- Specificity of HIRA and CAF-1 assembly factors
- Expression of tagged histones in HeLa cells
- Purification of H3.1 and H3.3 complexes
- H3.1 and H3.3 purified complexes
- Xenopus model offers rapid cell division
- Chromatin assembly pathways in Xenopus
- In-vitro chromatin assembly assays
- Variant-specific histone deposition pathways
- Model for "de-novo deposition"
- De-novo deposition & recycling of histones
- Summary of pathways
- Histone H3 variants in mammals: CENP-A
- Dynamics of CENP-A at centromeres
- Questions raised
- Conclusions
Topics Covered
- DNA is organized into chromatin which promotes compaction and brings about additional information
- the histone code hypothesis
- chromatin dynamics and heritability
- factors involved in chromatin dynamics
- nucleosomes disruption and assembly following DNA replication fork passage
- general steps in chromatin assembly
- histone chaperones and their possible roles (CAF-1, HIRA, ...)
- histone H3 variants and chromatin assembly coupled or not with DNA synthesis
- specific histone deposition pathways for each variant?
- "de-novo deposition" in addition to recycling old histones
- the maintenance of patterns of modifications in specific domains: how to ensure heritability?
Links
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Talk Citation
Almouzni, G. (2022, May 16). Histone dynamics, heritability and variants [Video file]. In The Biomedical & Life Sciences Collection, Henry Stewart Talks. Retrieved October 11, 2024, from https://doi.org/10.69645/MMII4336.Export Citation (RIS)
Publication History
Financial Disclosures
- Dr. Genevieve Almouzni has not informed HSTalks of any commercial/financial relationship that it is appropriate to disclose.
Update Available
The speaker addresses developments since the publication of the original talk. We recommend listening to the associated update as well as the lecture.
- Full lecture Duration: 38:24 min
- Update interview Duration: 4:38 min
A selection of talks on Genetics & Epigenetics
Transcript
Please wait while the transcript is being prepared...
0:00
In this talk, I'd like to discuss with you
the issue concerning histone dynamics,
their heritability, and their existence in the form of variants.
0:12
DNA in the nucleus is present in the form of chromatin,
and that consists of a complex together with proteins.
The main proteins found in chromatin are called histones.
They are small, basic proteins
called H3, H4, H2A, and H2B
for the core histones and H1 for the linker histone.
They ensure the compaction of DNA in the nucleus.
In the human cells about 2 meters of DNA
will fit in a volume of about a few micrometers
for the diameter of common somatic cells.
And this is represented here with a tennis ball on the right-hand panel.
So that will impose a problem of accessibility to the DNA
for all DNA transactions,
which thus necessitates dynamic properties
in order for all the metabolic pathways
of the DNA level to operate.
The additional aspect that histones can bring
in the chromatin organization
is a source of information.
Indeed, this organization can contribute to a differential use
of genetic information provided by the DNA
and thus, ensure a functional diversity
in the different cells.
Then the question that ensues is, how is it established,
and how can it be inherited?
If we now come to compaction,
1:36
which is the first aspect I wanted to present,
in the chromatin organization as depicted
by this watercolor, which was drawn by Nicolas Bouvier
from the ?"????
you can see that there are different levels
that ensure this compaction in the nucleus.
First, you have the DNA in the form of a helix,
which is wrapped around the core histones
to form the nucleosome—the sort of tennis ball that was represented before—
which then folds up further to give chromatin fibers,
which further fold up and then organize in the nucleus
to form different domains.
So this high level of compaction is
dynamic, and the enzymes that have to get access to DNA
have to deal with this kind of organization.
So if we get back to the DNA helix