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Regulation of Chromatin by FACT and NuA3 Chruscicki, Adam Tadeusz
Abstract
The presence of nucleosomes over vast regions of genome negatively influences transcription creating a need for temporal and structural regul ation of chromatin. The default transcription-repressive state can be countered by addition of post-translational modifications by ch romatin modifiers or chromatin alteration by histone chaperones. Chaperones alter chromatin structure before the RNAPII passage and restore it afterwards. How modifiers and chaperones function within chromatin is an area of intense research. Here we show how two complexes, the yeast FACT and NuA3 contribute to chromatin function. Yeast Facilitates Chromatin Transactions (yFACT) is a histone chaperone that maintains chromatin structure. The model of yFACT function in vivo is a subject of much debate. We provide evidence that yFACT acts by stably binding and altering nucleosomes. We also present the EM structure of yFACT associated with nucleosomes. We find that yFACT-associated nucleosomes are hyper-acetylated and show evidence for it being an effect of a direct interaction between yFACT and NuA3. At the same time, acetylation of the H3K56 residue by the histone acetyltransferase Rtt109, acts to recruit yFACT to chromatin through a nucleosome-dependent mechanism. To determine the distribution of yFACT- associated nucleosomes we constructed a map of yFACT-nucleosome localization at single-nucleosome resolution. We show that while yFACT-bound nucleosomes are distributed thought the genome they are also positioned over the canonical Nucleosome Depleted Regions (NDR). The yFACT- bound nucleosomes are positioned around TATA-elements and Nhp6 - target sequences genome-wide. Deletion of NHP6A/B leads to loss of chromatin at these loci. Our work suggests the first ever sequence-dependent mechanism of histone chaperone action in Saccharomyces cerevisiae. We also examined NuA3 recruitment to chromatin and showed that Yng1, a subunit of NuA3 with a known affinity for H3K4me3 is a bivalent protein. While as previously shown, the C-terminal PHD finer of Yng1 binds to H3K4me3, the N-terminus of Yng1 can also bind to unmodified chromatin. Although these motifs can bind independently, together they increase the apparent association of Yng1 with chromatin. Yng1 binding to chromatin is regulated by the HDA1 complex.
Item Metadata
Title |
Regulation of Chromatin by FACT and NuA3
|
Creator | |
Publisher |
University of British Columbia
|
Date Issued |
2013
|
Description |
The presence of nucleosomes over vast regions of
genome negatively influences
transcription creating a need for temporal and structural regul
ation of chromatin. The
default
transcription-repressive state can be countered by addition of post-translational
modifications by ch
romatin modifiers
or chromatin alteration
by
histone chaperones.
Chaperones alter
chromatin structure
before
the
RNAPII
passage
and restore it
afterwards. How
modifiers and chaperones function within chromatin is an area of
intense research.
Here
we show how two complexes, the yeast
FACT
and NuA3
contribute to
chromatin
function.
Yeast Facilitates Chromatin Transactions (yFACT) is a histone chaperone that
maintains chromatin structure.
The model of yFACT function
in vivo is a
subject of much
debate. We
provide evidence
that yFACT acts by stably binding and altering
nucleosomes. We also
present
the
EM structure of yFACT associated with
nucleosomes.
We find that yFACT-associated nucleosomes are hyper-acetylated and show evidence
for it being an effect of a direct interaction between yFACT and NuA3.
At the same time, acetylation of
the H3K56 residue by
the histone acetyltransferase
Rtt109, acts to recruit yFACT to chromatin through a nucleosome-dependent mechanism.
To determine
the distribution of yFACT-
associated nucleosomes
we
constructed
a map of yFACT-nucleosome
localization at
single-nucleosome
resolution. We show
that while yFACT-bound nucleosomes are distributed thought the
genome
they are also
positioned
over
the
canonical Nucleosome Depleted Regions (NDR).
The yFACT-
bound
nucleosomes
are positioned
around TATA-elements and
Nhp6
-
target sequences
genome-wide.
Deletion
of NHP6A/B
leads to
loss of
chromatin
at these loci. Our work
suggests
the first ever sequence-dependent mechanism of histone chaperone
action
in
Saccharomyces cerevisiae.
We also examined NuA3 recruitment to chromatin and
showed
that Yng1, a
subunit of NuA3 with a known affinity for H3K4me3 is a bivalent protein.
While
as
previously shown,
the C-terminal PHD finer of Yng1 binds to H3K4me3, the N-terminus
of Yng1 can
also
bind to unmodified chromatin.
Although these motifs
can bind
independently, together they increase the apparent association of Yng1 with
chromatin. Yng1 binding to chromatin is regulated by the HDA1 complex.
|
Genre | |
Type | |
Language |
eng
|
Date Available |
2014-04-30
|
Provider |
Vancouver : University of British Columbia Library
|
Rights |
Attribution-NonCommercial-NoDerivatives 4.0 International
|
DOI |
10.14288/1.0073776
|
URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
|
Graduation Date |
2013-05
|
Campus | |
Scholarly Level |
Graduate
|
Rights URI | |
Aggregated Source Repository |
DSpace
|
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Rights
Attribution-NonCommercial-NoDerivatives 4.0 International