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Updated: Mar 26, 2026
Isolation of Ribosome Bound Nascent Polypeptides in vitro to Identify Translational Pause Sites Along mRNA
Published on: July 6, 2012
Purification of Messenger Ribonucleoprotein Particles via a Tagged Nascent Polypeptide
Diana P Inchaustegui Gil1, Christine Clayton1
1Zentrum für Molekulare Biologie der Universität Heidelberg (ZMBH), DKFZ-ZMBH Alliance, Heidelberg, Germany.
Abstract:
The cytoplasmic fates of mRNAs are influenced by interactions between RNA-binding proteins and cis regulatory motifs. In the cytoplasm, mRNAs are present as messenger ribonucleoprotein particles, which include not only proteins that bind directly to the mRNA, but also additional proteins that are recruited via protein-protein interactions. Many labs have sought to purify such particles from cells, with limited success. We here describe a simple two-step procedure to purify actively translated mRNAs, with their associated proteins, from polysomes. We use a reporter mRNA that encodes a protein with three streptavidin binding peptides at the N-terminus. The polysomal reporter mRNA, with associated proteins, is purified via binding to a streptavidin matrix. The method takes four days, and can be applied in any cell that can be genetically manipulated. Using Trypanosoma brucei as a model system, we routinely purified 8% of the input reporter mRNA, with roughly 22-fold enrichment relative to un-tagged mRNAs, a final reporter-mRNA:total-mRNA ratio of about 1:10, and a protein purification factor of slightly over 1000-fold. Although the overall reporter mRNP composition is masked by the presence of proteins that are associated with many polysomal mRNAs, our method can be used to detect association of an RNA-binding protein that binds to specifically to a reporter mRNA.
Insights
Researchers developed a new method to purify actively translated messenger RNAs (mRNAs) and their bound proteins from cells. This technique uses a reporter mRNA and a streptavidin matrix for efficient isolation of messenger ribonucleoprotein particles (mRNPs).
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Messenger RNAs (mRNAs) form messenger ribonucleoprotein particles (mRNPs) in the cytoplasm, involving RNA-binding proteins and cis-regulatory motifs.
- Understanding mRNP composition is crucial for deciphering mRNA regulation, but purification of these complexes has been challenging.
Purpose of the Study:
- To develop a straightforward and efficient method for purifying actively translated mRNAs and their associated proteins from polysomes.
- To enable the study of protein interactions with specific mRNA molecules within their native cytoplasmic context.
Main Methods:
- A two-step purification procedure was established using a reporter mRNA encoding a protein with streptavidin-binding peptides.
- The reporter mRNA, within polysomes, was captured using a streptavidin matrix, isolating associated proteins.
- The method was validated in Trypanosoma brucei, a genetically manipulable model system.
Main Results:
- The purification method yielded approximately 8% of the input reporter mRNA with a 22-fold enrichment over un-tagged mRNAs.
- A final reporter-mRNA to total-mRNA ratio of about 1:10 was achieved, with a protein purification factor exceeding 1000-fold.
- The method successfully detected the association of a specific RNA-binding protein with the reporter mRNA.
Conclusions:
- This novel technique provides a robust approach for purifying actively translated mRNAs and their associated proteins.
- The method facilitates the identification of specific RNA-binding proteins and the characterization of mRNP composition.
- The procedure is applicable to any genetically manipulable cell, offering broad utility in molecular biology research.
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