Transcript DNA Methylation Histone Acetylation

Gene Silencing
Arlés Urrutia
Biomedicine and Biotechnology Institute.
Autonomous University of Barcelona. (IBB-UAB)
Neurochemistry Lab.
How do the many cell types of the body maintain
drastically different gene expression patterns
while sharing exactly the same DNA?
Evolutionary
SNP´s – CNV´s
Protein
Expression
Biochemical
Activity
CONTENT
• DNA methylation
– Methyl-CpG-binding proteins: MeCP2.
– De novo methyltransferase: Dnmt1.
– mSinA3 – HDAC Complex.
• Histone Modification.
– Acetilation & Methylation
• Chromatin Immunoprecipitation Assay
• Inheritance & Life Time
• Diseases & Therapies
DNA METHYLATION
Hemimethylated
HDAC1/2
mSin3A
mSin3A
MeCP2
HDAC1/2
HDAC1/2
MeCP2
mSin3A
HDAC1/2
MeCP2
Schematic diagram of the molecular mechanism of methylase inheritance and transcriptional
repression. HDAC1/2-mSin3A-MeCP2 Complex organized chromatin integrity. (Kimura, 2003)
HISTONE MODIFICATION
Carpenter (Abcam), 2005
Recruitment of Proteins to Histones. B. Proteins found that associated preferentially with
modified versions of histones H3 and histone H4. (Kouzarides, 2007)
HISTONE MODIFICATION
Gene Expression
H3K4me,
H3K36me (3) 
Methylation
RNApol II
Acetylation
H3K56Ac (+)
H4K16Ac (-)
DNA repair
DNA Replication
H4K20  Crb2
H4K20me,
H3K79me 
p53BP1
H3K56Ac,
H4K12Ac
Chromosome
Condensation
H3K9me 
H3S10ph
H4K12Ac, H4K8Ac,
H4K5Ac  HBO1 Pre-replicative
complex
H4K16Ac
(+) , (-) : activation or inhibition of the process.  throught the interaction with.
(Fuks, 2005)
HISTONE MODIFICATION
HAT
HDAC
HISTONE
CODE
Slide courtesy of Trevor Archer adapted from Jenuwein & Allis, Science 2001
15 February 2001
CHROMATIN IMMUNOPRECIPITATION ASSAY
INHERITANCE & LIFE TIME
Chromosome 15 (q11-13)
are deleted or unexpressed
MOTHER
FATHER
Angelman Syndrome.
neuro-genetic disorder
Happy demanor
Prade-Willi Syndrome
Maternal Allele Silenced.
Cognitive, Breathing and
feeding dificulties.
INHERITANCE & LIFE TIME
Mapping chromosomal regions with differential DNA methylation in MZ twins by using
comparative genomic hybridization for methylated DNA.
Presence of green and red signals that indicate hypermethylation and hypomethylation
events, whereas the 3-year-old twins have a very similar distribution of DNA methylation
indicated by the presence of the yellow color.
Fraga et al, 2005
DISEASES
Epigenetic therapy with
DNA methylation
inhibitors (DNMTi) and
HDAC inhibitors
(HDACi).
Combination therapies
are likely to gain
traction in the future
because of the inherent
self – reinforcing nature
of silencing
mechanisms.
Future breakthroughs could come from the use to epigenetic drugs to activate miRNAs
or use of drugs to target cancer stem cells after tumor debulking by estándar
chemotherapy. (Jones & Baylin, 2007)
INHERITANCE & LIFE TIME
Changing the view of what Inheritance is.
• Our parents life is affecting us directly, during the eggs and
embrio developments. Do the genes have memory?
• 30.000 genes is not enough for this ammount of differences
between individuals, even identical twins.
• The apereance of Beckwith-Wiedemann syndrome, (BWS) is
3/65 by In Vitro Fertilization in Victoria, AU. Could this
procedure trigger epigenetics switches for disseased?
• Is the imprinting an adaptation from the parents to the next
generation? The Overkalix case, in Sweden (food availability
and longevity).
The Experts
Spain Research . CNIO.
REFERENCES
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Williamson S. Christodoulou, J. (2006) Rett Syndrome: new clinical and molecular
insights. Eur J Hum Genet. 14, 896-903.
Fuks, F. (2005) DNA methylation and histone modifications: teaming up to silence
genes. Curr Opi in Genet & Develop. 15:1-6.
Kimura, H. Shiota, K. (2003) Methyl-CpG-binding protein, MeCP2, is target
Molecule for Maintenance DNA Methyltransferase, Dnmt1. J.Biol. Chem. 278:4806
– 4812.
Robertson, K. (2005) DNA methylation and human disease. Nature
Reviews,Genetics. 6:597.
Jones, P. Baylin, S. (2007) The Epigenomics of Cancer. Cell. 128:683-692.
Nan, X. Ng, HH. Johnson, C. Laherty, C. Turner, B. Eisenman, R. Bird, A. (1998)
Transcriptional repression by methyl-CpG-binding protein MeCP2 involves a
histone deacetylase complex. Nature Letters. 393:386-389.
Cullum, R. Alder, O. Hoodless, P. (2011) The Next generation: Using new
sequencing technologies to analyse gene regulation. Respirology. 16:210-222.