Results in weaker nucleosome bonds and more sliding
Trimethylation on an H3 Lysine -> more heterochromatin
Reader complex
Histone tails attract reader complexes that recruit other proteins.
Lysine acetylation is adding an acetyl group to the bottom (NH₃⁺) side of lysine.
Removes a lot of the polarity
Lysine methylation is adding many methyl groups where the hydrogen was on the nitrogen.
Reader-Writer complex
The writer complex can modify nucleosomes and histone tails.
Allows a reader to bind and recruit more writers sequentially.
“Eraser” complex
Removal of nucleosomes
Reverse the process through histone demethylase or histone deacetylase.
Barrier protein
Binds to DNA, preventing the spread of heterochromatin.
Centromeres and nucleosomes
Heterochromatin at the centromere is different from other heterochromatin because it is a different variant of the H3 histone. It is called Centromere Protein-A (CENP-A).
This lacks modifications found on regular H3
Attracts other nucleosome proteins
Creates a denser nucleosome packing than normal to form the kinetochore.
Chromatin to Chromosome
Creates loops on the sister chromatid
The chromosome scaffold is used almost as a cytoskeleton-esque frame for chromosomes.
