Figure 5.

Summary of intact protein MS and tandem MS/MS data from a time course showing that O-GlcNAcylation can take place over the entire CTD. The highly repetitive CTD2–30 region of SUMO-CTD52 is highlighted in dark gray, and less conserved CTD1 and CTD32–47 are highlighted in light gray. The numbers of O-GlcNAc residues are colored red. For example, “0–3” represent unmodified, singly, doubly, and triply O-GlcNAcylated CTD peptides, respectively. The peptides containing the same total number of O-GlcNAc modifications could vary in their modification sites, but our current study cannot unambiguously map O-GlcNAcylation sites on a particular CTD heptad repeat. Peptide CTD48–52 (white) was not detected (N). Results shown here could be reproduced from two biological analyses at each time point.