Chromatin and Epigenetics

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Chromatin and Epigenetics

• Tohoku Univerisity
• Prof. Masahiko HARATA

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Genetics
Genome-A
Genome-B
Epigenetics
Genome-C
Brain
Genome-C
Muscle
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What is chromatin?
Nucleosome (basal unit) Various nuclear proteins
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nucleosome
core histones
DNA
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chromatin fiber
Nucleus
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Chromatin structure regulates genome function.
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transcriptional machinery
histone modification complexes
gene expression
inactive chromatin
active chromatin
chromatin remodeling complexes
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ATP-dependent chromatin remodeling
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A schematic model for chromatin remodeling
chromatin remodeling complex
nucleosome
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Examples of chromatin remodeling complex
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Histone modification
Acetylation Methylation Phosphorylation
..etc
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A schematic model for histone acetylation
Histone acetyltransferase (HAT)
Histone deacetylase (HDAC)
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An example of chromatin remodeling complex
involved in cell differentiation
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Examples of chromatin remodeling complex
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ArpNa and ArpNb are localized in the nucleus
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Brain specific expression of ArpNa
cDNA
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The deduced three-dimensional structures of ArpNa
and b
??specific region
?-specific region
expressed only in brain
expressed in all tissues
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CtBP (C-terminal binding protein) transcriptiona
l co-repressor
NAD/ NADH
HDAC Polycomb
Kumer et al. Mol. Cell 10, 857-869 (2002)
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ArpNa-dependent transcription repression by CtBP
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A schematic model of the different functions of
ArpNa and b in mammalian SWI/SNF complex
other tissues
HAT
ArpN?
SWI/SNF complex
transcription factor
Transcription
brain
HDAC
CtBP
ArpNa
PcG?
SWI/SNF complex
transcription factor
Transcription
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Expression of mArpNa and b genes during neural
differentiation of P19 cells
RTase
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Morphology and cadherins-expression of P19 cells
expressing hArpNa
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An example of the involvement of chromatin
remodeling in DNA repair
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repair machinery chromatin modulation?
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Immunofluorescence analysis of S- and M-phase
cells with anti-hIno80 polyclonal antibody
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Immunofluorescence analysis of S- and M-phase
cells with anti-hArp5 polyclonal antibody
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Co-immunoprecipitation of hIno80 and hArp5
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Hypersensitivity of hArp5-knock down cells to DNA
damage
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hArp5 knock down impaired the damage dependent
accumulation of ?-H2AX
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DNA damage-dependent accumulation of ?-H2AX in
chromatin is increased by overexpression of
hIno80-Flag together with hArp5-HA
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H2AX
H2AX
H2AX
H2AX
REMODEL
REMODEL
H2AX
H2AX
REMODEL
REMODEL
P
P
spread
spread
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Genetics
Genome-A
Genome-B
Epigenetics
Genome-C
chromatin
Brain
Genome-C
Muscle
chromatin