Specific and Efficient N-propionylation of histones with Propionic acid N-hydroxysuccinimide Ester for Histone Marks Characterization by LC-MS

Histones participate in transcriptional regulation via a variety of dynamic posttranslational modifications (PTMs) on them. Mass spectrometry (MS) has become a powerful tool to investigate histone PTMs. With the Bottom-up mass spectrometry approach, chemical derivatization of histones with propionic anhydride or deuterated acetic anhydride followed by trypsin digestion was widely used to block the hydrophilic lysine residues and generates compatible peptides for LC-MS analysis. However, some serious side reactions (such as acylation on tyrosine or serine) caused by acid anhydrides will lead to a number of analytical problems such as reducing the accuracy and impairing reproducibility and sensitivity of analysis. Thereby we report a novel derivatization method that utilizes N-HydroxySuccinimide ester to specifically and efficiently derivatize both free and monomethylated amine groups in histones. A competitive inhibiting strategy was implemented in our method to effectively avoid the side reactions. We demonstrated that our method can achieve excellent specificity and efficiency for histones derivatization in a reproducible manner. To test in vivo samples, we applied the derivatization method to quantitatively profile the histone PTMs in the KMS11 cell line with selective knock out of the translocated NSD2 (a histone methyltransferase that catalyzes the histone H3 lysine 36 methylation) and its parental cells. Comparative quantification revealed a significant crosstalk between H3 protein K27 methylation and adjacent K36 methylation