Live Cell Imaging of Bioorthogonally Labelled Proteins Generated With a Single Pyrrolysine tRNA Gene

Noa Aloush, Tomer Schvartz, Andres I. König, Sarit Cohen, Eugene Brozgol, Benjamin Tam, Dikla Nachmias, Oshrit Ben-David, Yuval Garini, Natalie Elia, Eyal Arbely

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

Genetic code expansion enables the incorporation of non-canonical amino acids (ncAAs) into expressed proteins. ncAAs are usually encoded by a stop codon that is decoded by an exogenous orthogonal aminoacyl tRNA synthetase and its cognate suppressor tRNA, such as the pyrrolysine synthetase/tRNACUAPyl pair. In such systems, stop codon suppression is dependent on the intracellular levels of the exogenous tRNA. Therefore, multiple copies of the tRNAPyl gene (PylT) are encoded to improve ncAA incorporation. However, certain applications in mammalian cells, such as live-cell imaging applications, where labelled tRNAs contribute to background fluorescence, can benefit from the use of less invasive minimal expression systems. Accordingly, we studied the effect of tRNAPyl on live-cell fluorescence imaging of bioorthogonally-labelled intracellular proteins. We found that in COS7 cells, a decrease in PylT copy numbers had no measurable effect on protein expression levels. Importantly, reducing PylT copy numbers improved the quality of live-cell images by enhancing the signal-to-noise ratio and reducing an immobile tRNAPyl population. This enabled us to improve live cell imaging of bioorthogonally labelled intracellular proteins, and to simultaneously label two different proteins in a cell. Our results indicate that the number of introduced PylT genes can be minimized according to the transfected cell line, incorporated ncAA, and application.

Original languageEnglish
Article number14527
JournalScientific Reports
Volume8
Issue number1
DOIs
StatePublished - 1 Dec 2018

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