Post-translational modifications of histone can positively or negatively regulate gene activity, but the full scope of such modifications and their functions are still being determined. In eLife, Schneider and colleagues use mass spectrometry to identify a previously uncharacterized form of histone modification: acetylation of histone H3 at Lys64 (H3K64ac). H3K64ac associates with euchromatin and the transcriptional start sites of active genes and opposes its repressive counterpart, the trimethylated histone H3K64me3. Acetylation of H3K64 occurs on the lateral surface of the histone octamer and is facilitated by the coactivator p300-CBP. The addition of H3K64ac results in destabilization of the nucleosome and gene transcription. This activation mark is found in diverse cell types, including lymphoid cells, and may therefore have important and widespread roles in controlling gene transcription.

eLife (25 March 2014) doi:10.7554/eLife.01632