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Sm-ChIPi: Single-Molecule Chromatin Immunoprecipitation Imaging
Roubina Tatavosian1, Xiaojun Ren2
1Department of Chemistry, University of Colorado Denver, Denver, CO, 80217-3364, USA.
Methods in Molecular Biology (Clifton, N.J.)
|October 14, 2017
Summary
Researchers developed single-molecule chromatin immunoprecipitation imaging (Sm-ChIPi) to visualize epigenetic complex assembly on chromatin. This method quantifies protein complex stoichiometry on nucleosomes, advancing our understanding of chromatin regulation.
Area of Science:
- Molecular Biology
- Epigenetics
- Chromatin Dynamics
Background:
- Epigenetic complexes are crucial for regulating chromatin dynamics.
- Understanding how these complexes bind and assemble on chromatin in cells is limited by technical challenges.
Purpose of the Study:
- To introduce a novel method, single-molecule chromatin immunoprecipitation imaging (Sm-ChIPi), for assessing epigenetic complex assembly stoichiometry on chromatin within cells.
Main Methods:
- Sm-ChIPi combines chromatin immunoprecipitation with single-molecule fluorescence microscopy.
- It involves expressing fluorescently tagged epigenetic complex subunits in knockout cells.
- Isolated nucleosome-epigenetic complex assemblies are imaged using single-molecule TIRF microscopy, with stoichiometry determined by photobleaching analysis.
Main Results:
- Sm-ChIPi enables direct visualization and quantification of single protein-epigenetic complex interactions on nucleosomes.
- The method accurately infers the number of protein complex copies per nucleosome.
Conclusions:
- Sm-ChIPi is a sensitive and direct technique for measuring the cellular assembly stoichiometry of epigenetic complexes on chromatin.
- This approach overcomes previous technical limitations in studying chromatin binding and assembly mechanisms.