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Updated: Apr 3, 2026
07:26
Site Specific Lysine Acetylation of Histones for Nucleosome Reconstitution using Genetic Code Expansion in Escherichia coli
Published on: December 26, 2020
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Nucleosome competition reveals processive acetylation by the SAGA HAT module.
Alison E Ringel1, Anne M Cieniewicz2, Sean D Taverna2
1Department of Biophysics and Biophysical Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD 21205;
Summary
The Spt-Ada-Gcn5 acetyltransferase (SAGA) complex uses Sgf29 to recognize histone H3K4me3 marks, promoting targeted histone acetylation. This mechanism explains how SAGA regulates gene transcription at promoters.
Area of Science:
- Epigenetics
- Molecular Biology
- Gene Regulation
Background:
- The Spt-Ada-Gcn5 acetyltransferase (SAGA) complex is crucial for gene transcription.
- SAGA's histone acetyltransferase (HAT) module, containing Gcn5, is responsible for histone hyperacetylation.
- Histone 3 lysine 4 trimethylation (H3K4me3) is a mark enriched at active gene promoters.
Purpose of the Study:
- To elucidate the mechanism by which H3K4me3 recognition by Sgf29 leads to histone hyperacetylation by Gcn5.
- To understand the role of Sgf29's Tudor domain in mediating the interaction between H3K4me3 and Gcn5 activity.
Main Methods:
- Utilized differential fluorescent labeling of histones to monitor acetylation of distinct nucleosome subpopulations.
- Compared acetylation of H3K4me3-modified nucleosomes versus unmodified nucleosomes in vitro.
- Investigated the requirement of Sgf29's Tudor domain for H3K4me3-dependent acetylation.
Main Results:
- The SAGA HAT module preferentially acetylates H3K4me3 nucleosomes over unmodified nucleosomes.
- This preferential acetylation requires the Tudor domain of Sgf29.
- H3K4me3 promotes processive, multisite acetylation of histone H3 by Gcn5.
Conclusions:
- Established a model for Sgf29 function at gene promoters, linking H3K4me3 recognition to Gcn5 activity.
- Defined a mechanism for crosstalk between histone modifications (H3K4me3) and histone acetylation.
- Explained how SAGA establishes distinct acetylation patterns at promoters versus coding regions.
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