Identification and Initial Characterization of Histone Lysine Propionylation and Lysine Butyrylation Pathways

Protein post‐translational modifications (PTMs) in histones play a crucial role in chromatin‐templated cellular processes. At least 10 types of histone PTMs were described in the past. However, it remains unknown if previously undescribed PTMs exist in histones. Using mass spectrometry, we recently identified lysine propionylation and lysine butyrylation as two novel PTMs in histones, which are structurally similar to lysine acetylation. We validated structures of these histone PTMs by three independent methods: (i) tandem mass spectrometry of synthetic peptides, (ii) co‐elution in HPLC, and (iii) Western blotting using sequence‐specific and pan antibodies. Using pan antibodies against the two PTMs, we showed that these two PTMs are abundantly present in core histones among several eukaryotic species we examined. We demonstrate that p300 and CBP, two acetyltransferases, can catalyze lysine butyrylation reactions, while HDAC3 is lysine debutyrylation enzyme for histone butyrylation. ChIP‐qPCR assay and ChIP‐on‐chip experiments indicate that histone lysine butyrylation is associated with transcriptional regulation and with various genomic locations in a similar fashion as lysine acetylation. Our results therefore provide the first snapshot of the new histone PTMs and suggest the higher complexity of the histone PTMs.