Download Twenty-five years of the nucleosome Kornberg and Lorch 1998, Cell

Survey
yes no Was this document useful for you?
   Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Document related concepts

Minimal genome wikipedia, lookup

Polyploid wikipedia, lookup

Gene wikipedia, lookup

Designer baby wikipedia, lookup

History of genetic engineering wikipedia, lookup

Transcription factor wikipedia, lookup

Microevolution wikipedia, lookup

Epigenetics of depression wikipedia, lookup

Long non-coding RNA wikipedia, lookup

Artificial gene synthesis wikipedia, lookup

X-inactivation wikipedia, lookup

Vectors in gene therapy wikipedia, lookup

Point mutation wikipedia, lookup

Cancer epigenetics wikipedia, lookup

Therapeutic gene modulation wikipedia, lookup

Primary transcript wikipedia, lookup

Neocentromere wikipedia, lookup

Epigenetics of diabetes Type 2 wikipedia, lookup

Epigenetics of neurodegenerative diseases wikipedia, lookup

Epigenetics wikipedia, lookup

Chromosome wikipedia, lookup

Nutriepigenomics wikipedia, lookup

Epigenetics in stem-cell differentiation wikipedia, lookup

Epigenetics of human development wikipedia, lookup

Epigenomics wikipedia, lookup

Epigenetics in learning and memory wikipedia, lookup

Histone acetyltransferase wikipedia, lookup

Polycomb Group Proteins and Cancer wikipedia, lookup

Nucleosome wikipedia, lookup

NEDD9 wikipedia, lookup

Transcript
Twenty-five years of the
nucleosome
Kornberg and Lorch 1998, Cell 98: 285.
HATs
HDACs
Important point• P289- Although acetylation of histone tails
may counteract condensation of
nucleosomes in chromatin fibers, it is
unlikely to disrupt the structure of the core
particle for transcription
• Why? Tails are outside of the core, make
little contribution to overall structure
• Chromatin remodeling enzymes are likely
responsible for nucleosome disruption
Chromatin remodeling
• SWI/SNF proteins are chromatin remodelers
• These disrupt nucleosome in an ATPdependent fashion (ATPase activity)
• Models– displacement
– octamer sliding
Histones- modifications and function
Michael Hagmann 1999 Science 285:1203
•
A. Phosphorylation of histones
• two opposing functions reported
» opening chromatin
» condensing chromatin (cell division)
I. Phosphorylation
• Immunocytochemistry
with anti-phosphoH3
antibody
• Phosphorylation of H3
observed during
mitosis
• Growth factor
stimulation- observe
~100 speckels in cells,
randomly distributed
– correlates with # of
genes that respond to
growth factor stimuli.
– Identify a 90 Kd
protein
Cellular and Molecular Genetics BLA510 Spring 2001
Gary A. Bulla, PhD
B. Coffin Lowry syndrome- mental retardation
and a defect in growth factor response
• mutation identified in in Rsk-2 gene
•Immunocytochemistry with anti-phosphoH3 Ab
-no speckles observed
Growth factor
Receptor
MAP kinase signal
transduction
pathway
Thus, Rsk-2
mutation
prevented H3
phosphorylation
Ras
Raf (MAPKKK)
MEK
(MAPKK)
ERK
RSK-2
H3
P
H3
( MAPK)
ExperimentInduce cells with growth factors,
Crosslink DNA+ proteins, then
immunoprecipitate with anti-Phospho-H3 Ab
Most genes H3
Crosslink,
nuclease
H3
c-fos
P H3
P
DNA
H3
Immunoprecipitate
with anti-Phospho-H3
Thus, known growthresponse genes are
bound by histones
with phosphorylated
H3
Agarose gel
Southern
Probe with labeled
c-fos DNA
C. Role in phosphorylation in cell division
1. Tetrahymena
# copies of
chromosomes
macronucleus
90
micronucleus
2
Mode of replication
in cell division
Pinching off
Normal mitosis
Affect of H3 mutation
at phosphorylation site
none
abnormal condensation
chromosome loss
Tetrahymena
(a protozoan)
Genetics, Russell, p6.
Tetrahymena- Histone H3 phosphorylation occurs
only in mitotic micronuclei
Macronuclei
Micronuclei
Mitotic (football shape)
2. Immunocytochemistry- observe phospho-H3 throughout
chromosomes during cell division
Thus, this must play a role is chromosome condensation during mitosis
3. Models1. Phosphorylation + acetylation allows activation of
gene expression, depending on context
2. Phospho-H3 loosens chromatin, enhancing transcription
factor binding or mitotic factor binding
II. Methylation
CARM-1 -
• activates transcription (coactivator)
• methylates proteins
• inactivation of methylation activity - lose
transcriptional activation
• methylates histone H3 in vitro
• what are CARM-1 targets??
coactivator
Steroid hormone receptor
CARM-1
p160
Me H3
+1
TATAA
III. Acetylation- Bromodomain -100 AA found in
~30 chromatin associated proteins (inc. HATs)
- may be binding motif for actetylated histones
Acetylated lysine
IV. Other modifications- ubiquitination, glycosylation
Methylation, phosphorylation and acetylation of histones
OFF
Histone H3
ON
Bromodomain
of a HAT
Chromodomain
of a chromatin
remodeler
Science 292:65, 2001
Is there a “Histone Code”?
• Definition- “Covalent modifications of
histones constitute an intricate pattern that
creates a docking surface with which the
modules of other proteins can interact”
Shelley Berger, Wistar Institute
Science 292:65, 2001