To study epigenetic inheritance, yeast silent heterochromatin provides an excellent model. Previously, we developed an in vitro assembly system to demonstrate the formation of filament structures with requirements that mirror yeast epigenetic gene silencing in vivo However, the properties of these filaments have not been investigated in detail. Here, we show that the assembly system requires Sir2, Sir3, Sir4, nucleosomes and O-acetyl-ADP-ribose. We also demonstrate that all Sir proteins and nucleosomes are components of these filaments to prove they are SIR-nucleosome filaments. Furthermore, we show that the individual localization patterns of Sir proteins on the SIR-nucleosome filament reflects those patterns on telomeres in vivo In addition, we reveal that magnesium exists in the SIR-nucleosome filament, with a role similar to that for chromatin condensation. These results suggest that a small number of proteins and molecules are sufficient to mediate the formation of a minimal yeast silent pre-heterochromatin in vitro.
Date:
2017-01
Relation:
Molecular Biology of the Cell. 2017 Jan;28(3):381-386.
