Use of the Peptide Barcode Method for Efficient Screening of mRNA Expression Control Sequence.

The precise control of specific protein expression in target cells remains a critical challenge for the advancement of messenger RNA (mRNA) therapeutics. While incorporating regulatory sequences, such as microRNA-responsive RNA switches, is a promising approach for cell-type-specific targeting, optimizing these sequences requires extensive and time-consuming screening using conventional evaluation methods. In this study, we applied a multiplexed evaluation methodology utilizing peptide barcodes coupled with liquid chromatography-mass spectrometry (LC-MS) to improve the screening and design efficiency of mRNA expression control sequences. We designed mRNAs equipped with cell-specific expression control sequences and fused unique peptide barcodes to the encoded target proteins. By comparing conventional individual transfections with simultaneous co-transfections, we demonstrated that our LC-MS-based method can successfully distinguish and quantify protein expression derived from individual mRNA candidates within a single mixed sample. The simultaneous evaluation using peptide barcodes yielded results equivalent to the individual evaluations but required a reduced number of samples. This multiplexed technology would accelerate the screening process for regulatory sequences and is expected to enhance the development of mRNA therapeutics with high targeting specificity.