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Epigenetik: Von der Genomforschung zur Epigenomforschung. 4362. 4355. Exploring the hierarchy of epigenetic mechanisms. Chromosome territories, chromatin fibers and domains, interchromatin compartment, topology of active and silent genes. Histone modifications and chromatin remodelling.
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Exploring the hierarchy of epigenetic mechanisms Chromosome territories,chromatin fibers and domains, interchromatin compartment, topology of active and silent genes Histone modifications and chromatin remodelling DNA methylation Horn and Peterson, 2002
0777 Metaphasechromomen aus einer diploiden, menschlichen Zelle in der Mitose
1. Herstellung von Metaphase-Präparaten aus Vollblutkulturen Markieren der Sonde mit Reportermolekülen (Biotin, etc.) bzw. Fluoreszenzfarbstoffen 3. Denaturierung der Sonden- und Ziel-DNA Sonden Ziel-DNA 4. Hybridisierung der Sonde an die komplementären Ziel-DNA Sequenzen; bei indirekter Markierung anschließende Immunodetektion 5. Visualisierung der Fluoreszenz- signale Sonde Ziel-DNA Fluoreszenz in situ Hybridisierung (FISH) 2. Herstellung der DNA-Sonde
3D map of chromosome territory arrangements in postmitotic human fibroblast cell nuclei (G0) “true color“ image (RGB) 24 color painting of all chromosome territories in male diploid human fibroblast nucleus classification (M-FISH 3D-program) Bolzer et al, 2005
the DNA sequence levelthe textbook story • linear array of sequence elements • transcription units • promoters, enhancers, silencers • sequences guide the machineries for transcription
X m m AACGAGATCGTTCGAA AACGAGATCGTTCGAA X HeinrichLeonhardt
DNA Methylierung Heinrich Leonhardt
de novo methylation Heinrich Leonhardt
Transcriptional repression through DNA methylation HeinrichLeonhardt
the chromatin level histone modifications • methylation,acetylation, phosphorylation, ubiquitinylation chromatin remodelling • ATP-dependent shiftingof nucleosomes
Modification sites at the N-termini of histone tails Modifications above an amino acid are linked to transcriptionally active chromatin Modifications below an amino acid are linked to transcriptionally inactive chromatin K= Lysin, R= Arginin, S= Serin, Note that methylation can exist in a mono-, di- or trimethylated state
Currently used antibodies against histone modification sites Transcriptionally active (eu)chromatin Mono-methyl H3-K9 Mono-methyl H4-K20 Unknown (active chromatin?) Transcriptionally active (eu)chromatin Acetyl-H4-K8 Tri-methyl H3-K27 Facultative Heterochromatin Transcriptionally repressed and Constitutive (hetero)chromatin Tri-methyl H3-K9 Tri-methyl H4-K20 H3/H4-multi-methyl lysine (MML) sites Mostly repressed chromatin
N Lysine in histone: O O C C C - g e P N+ d DNA a b C C O cell membrane C O O [3H]-Ac Acetyl-CoA HAT (Histone Acetyl- Transferase) HDAC (Histone DeACetylase) C O C - O CoA N Uncharged Acetyl-Lysine in histone C C C N C e C C C C O O Histone Acetylation Enzymes Jakob Waterborg WaterborgJ@umkc.edu
+ charged histone tail acetylated histone tail Function of Histone Acetylation 30 nm 11 nm HIGH in histone H1 Often low in histone H1 Jakob Waterborg WaterborgJ@umkc.edu