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Immunofluorescent Staining for Visualization of Heterochromatin Associated Proteins in Drosophila Salivary Glands
Published on: August 21, 2021
HP1 loses its chromatin clustering and phase separation function across evolution.
Sanâa Bensaha1, Dominika Lewandowska1, Fernando Muzzopappa1
1MCD, Center for Integrative Biology (CBI), University of Toulouse, CNRS, Toulouse, France.
Heterochromatin protein 1 (HP1) from yeast and flies phase separates, unlike mouse HP1. This protein phase separation influences heterochromatin organization but has minor effects on gene expression.
Area of Science:
- Cell Biology
- Molecular Biology
- Genetics
Background:
- Heterochromatin protein 1 (HP1) is a conserved protein implicated in heterochromatin formation.
- HP1's role in driving heterochromatin formation via phase separation is debated due to conflicting evidence across systems.
Purpose of the Study:
- To comparatively assess the in vitro and in vivo phase separation behavior of HP1 homologs from diverse species (fission yeast, fruit fly, mouse).
- To investigate the impact of HP1-induced heterochromatin coalescence on gene expression.
- To elucidate the evolutionary factors influencing HP1 phase separation propensity.
Main Methods:
- In vitro phase separation assays.
- In vivo studies using mammalian cells to observe heterochromatin coalescence.
- Analysis of HP1 intrinsic disorder and paralog interactions.
Main Results:
- HP1 from fission yeast and fruit fly exhibit liquid-liquid phase separation, unlike mouse HP1.
- Heterochromatin coalescence induced by yeast and fly HP1 in mouse cells had minimal impact on gene expression.
- Decreasing phase separation propensity in HP1 homologs correlates with reduced intrinsic disorder and increased sensitivity to antagonistic paralogs.
Conclusions:
- HP1 phase separation capability varies across species, with yeast and fly HP1 being more prone to phase separation than mouse HP1.
- HP1-mediated heterochromatin organization has limited effects on gene expression.
- Evolutionary changes in intrinsic disorder and paralog interactions shape HP1 phase separation dynamics and nuclear organization control.

