Immunoprecipitation of Reporter Nascent Chains from Active Ribosomes to Study Translation Efficiency

Area of Science:

• Molecular Biology
• Gene Expression Regulation
• Biochemistry

Background:

• Understanding gene expression requires studying translation efficiency (TE).
• Existing methods for measuring TE, like ribosome profiling and reporter assays, can be complex and labor-intensive.
• There is a need for simpler, more accessible methods to investigate TE at the individual gene level.

Purpose of the Study:

• To introduce a straightforward biochemical reporter assay for studying mRNA translation efficiency.
• To present Nascent Chain Immunoprecipitation (NC IP) as a method for analyzing TE of mRNAs from transfected plasmids.
• To demonstrate the utility of NC IP in investigating UTR-dependent TE regulation and discriminating translating from non-translating mRNAs.

Main Methods:

• Developed Nascent Chain Immunoprecipitation (NC IP), a plasmid-based assay.
• Utilizes immunoprecipitation of N-terminally Flag-tagged nascent polypeptide chains from elongating ribosomes.
• Quantifies eluted mRNA via quantitative reverse transcription polymerase chain reaction (RT-qPCR) after release with puromycin or Flag peptide.

Main Results:

• The NC IP assay successfully measures translation efficiency of user-selected mRNAs.
• Demonstrated UTR-dependent regulation of translation efficiency using the NC IP method.
• The assay effectively distinguishes actively translating mRNAs from non-translating ones.

Conclusions:

• NC IP provides a simple, efficient, and standard laboratory equipment-based method for studying mRNA translation.
• This technique can be applied to investigate the impact of various factors, including microRNAs, drugs, and genetic backgrounds, on TE.
• The NC IP protocol is adaptable for use in different organisms, such as mammalian cells and budding yeast.