Ebert review 2006, chromatin modifications in Drosophila
An inversion of on X places the white gene near heterochromatin, which results in varigated eyes — stochastic deactivation. 500 surpressors and enhancers, 3 of which are dose dependant and encode ‘chromatin proteins’, including H3K9 methyltransferase.
is this due to stochastic decondensation boundaries (some cells don’t form heterochormatin spanning w) or due to some expression of w from within the heterochromatin region?
Mono-methylation of H3K9 is controlled by a different enzyme than Su(var)3,9, which does di and tri-methylation. HP1 (heterochromatic protein 1) doesn’t associate until tri-methylated. All H3K9 much more dominant near centromere.
H3K27 distributed throughout chromosome, found in heterochromatin bands. become less frequent and more sharply defined increasing from mono to trimethylation. in vivo evidence suggests all H3K27 me is done by E(Z).
H3K20me also common in heterochromatin
H3K4me2 definitely in euchromatin. Found in all open bands.
H3K9 found in specific subset of open bands.
Do redundant proteins decrease noise by allowing for reduced correlation times in concentration fluctuations?
Lan and Shi 2009 — histone methylation (primarily what’s known about how heriditability of histone methyl states works.
Reinberg 2011 Polycomb review
Paro 2011 — Gene silencing review
Can we use single cell studies to probe the efficiency of transfer of methyl-repressive states to daughter cells?