Genetic Incorporation of Nε-Formyllysine, a New Histone Post-translational Modification

Lysine formylation is a newly discovered post-translational modification (PTM) in histones and other nuclear proteins; it has a well-recognized but poorly defined role in chromatin conformation modulation and gene expression. To date, there is no general method to site-specifically incorporate N-epsilon-formyllysine at a defined site of a protein. Here we report the highly efficient genetic incorporation of the unnatural amino acid N-epsilon-formyllysine into proteins produced in Escherichia coli and mammalian cells, by using an orthogonal N-epsilon-formyllysine tRNAsynthetase/tRNA(CUA) pair. This technique can be applied to study the role of lysine formylation in epigenetic regulation.