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Updated: Jul 4, 2026
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In Vitro Ubiquitination and Deubiquitination Assays of Nucleosomal Histones
Published on: July 25, 2019
Polyubiquitylation of histone H2B
Fuqiang Geng1, William P Tansey
1Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724, USA.
Molecular Biology of the Cell
|June 20, 2008
Summary
Histone H2B ubiquitylation, crucial for gene regulation and DNA repair, is not solely monoubiquitylation. Yeast H2B undergoes extensive polyubiquitylation via distinct pathways, suggesting ubiquitin chains, not single ubiquitin, mediate its functions.
Area of Science:
- Epigenetics
- Molecular Biology
- Yeast Genetics
Background:
- Histone ubiquitylation is a key epigenetic modification regulating chromatin functions.
- Histone H2B ubiquitylation at K123 in yeast is a well-studied example, generally assumed to be monoubiquitylation.
- This modification impacts gene silencing, activation, and DNA repair.
Purpose of the Study:
- To re-examine the ubiquitylation status of endogenous histone H2B in yeast.
- To challenge the prevailing assumption of H2B monoubiquitylation.
- To elucidate the mechanisms and biological significance of H2B ubiquitylation.
Main Methods:
- Analysis of endogenous histone H2B ubiquitylation in Saccharomyces cerevisiae.
- Investigation of different ubiquitylation pathways and their regulatory machinery.
- Characterization of ubiquitin chain formation and deubiquitylation enzymes.
Main Results:
- Contrary to expectations, yeast histone H2B is extensively polyubiquitylated, not just monoubiquitylated.
- Two distinct modes of H2B polyubiquitylation were identified: one at K123 (Rad6-Bre1 dependent) and another on multiple lysines (by uncharacterized ligases).
- These polyubiquitylation events are differentially regulated by various ubiquitin-specific proteases, indicating distinct biological roles.
Conclusions:
- Histone H2B ubiquitylation can occur as polyubiquitin chains, not solely as monoubiquitylation.
- The biological effects of H2B ubiquitylation may be mediated by ubiquitin chains, expanding our understanding of this epigenetic mark.
- Distinct ubiquitylation pathways and deubiquitylation regulation suggest complex functional outcomes for H2B modification.
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