Assessing Self-interaction of Mammalian Nuclear Proteins by Co-immunoprecipitation
Claudia Cattoglio1,2,3,4, Iryna Pustova1,2,3,4, Xavier Darzacq1,2,3
1Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA.
Insights
This study introduces a refined co-immunoprecipitation (CoIP) protocol to analyze protein self-association, particularly for nuclear proteins. The method, termed self-CoIP, reliably assesses protein self-interaction and the influence of nucleic acids.
Area of Science:
- Molecular Biology
- Biochemistry
- Cell Biology
Background:
- Protein-protein interactions are fundamental to biological processes.
- Co-immunoprecipitation (CoIP) is a key method for studying these interactions.
- Nuclear protein clustering suggests frequent self-association, requiring biochemical validation.
Purpose of the Study:
- To develop and optimize a CoIP protocol for testing nuclear protein self-association.
- To investigate the role of nucleic acids in protein self-interaction.
- To provide a robust method for analyzing homotypic and heterotypic interactions.
Main Methods:
- Developed a specific co-immunoprecipitation protocol (self-CoIP) for endogenously tagged nuclear proteins.
- Optimized the protocol to assess protein self-association (homotypic interactions).
- Evaluated the protocol's ability to test heterotypic interactions and the role of nucleic acids.
Main Results:
- The self-CoIP protocol is reliable and robust for studying nuclear protein self-association.
- The method successfully validates homotypic and heterotypic protein-protein interactions.
- The protocol can be used to explore the influence of nucleic acids on these interactions.
Conclusions:
- The optimized self-CoIP protocol provides a valuable biochemical tool for studying protein self-association.
- This method addresses the need for orthogonal approaches to validate protein clustering observations.
- The protocol is versatile for analyzing various protein-protein interactions in nuclear contexts.
Abstract:
Protein-protein interactions constitute the molecular foundations of virtually all biological processes. Co-immunoprecipitation (CoIP) experiments are probably the most widely used method to probe both heterotypic and homotypic protein-protein interactions. Recent advances in super-resolution microscopy have revealed that several nuclear proteins such as transcription factors are spatially distributed into local high-concentration clusters in mammalian cells, suggesting that many nuclear proteins self-interact. These observations have further underscored the need for orthogonal biochemical approaches for testing if self-association occurs, and if so, what the mechanisms are. Here, we describe a CoIP protocol specifically optimized to test self-association of endogenously tagged nuclear proteins (self-CoIP), and to evaluate the role of nucleic acids in such self-interaction. This protocol has proven reliable and robust in our hands, and it can be used to test both homotypic and heterotypic (CoIP) protein-protein interactions.
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