5-Ethynyl uridine (5-EU) is a modified nucleoside that can be used for labeling of nascent RNA inside cells. After feeding EU, it can react with azides. Our own experiments indicate that it will be first integrated in de novo synthesized RNA, but we have also observed incorporation into DNA after some incubation time. This is most likely via conversion of the EU ribonucleoside into EdU aided by intracellular ribonucleotide reductases. Research from several groups demonstrates successful EU cellular labeling for divers applications.

LITERATURE

Exploring RNA transcription and turnover in vivo by using click chemistry, C. Y. Jao et al., 2008, Proc. Natl. Acad. Sci. U. S. A., Vol. 105, p. 15779–15784.

https://doi.org/10.1073/pnas.0808480105

Capturing the interactome of newly transcribed RNA, X. Bao et al., 2018, Nature Methods, Vol. 15, p. 213-220.

https://doi.org/10.1038/nmeth.4595

Visualization of the Nucleolus Using Ethynyl Uridine, M. Dvořáčková et al., 2018, Frontiers in Plant Science, Vol. 9(177).

https://doi.org/10.3389/fpls.2018.00177