N-terminal methylation levels of CENP-B were influenced by cellular stress, but not by metaphase arrest. MS analysis showing the relative abundances of different methylation forms of N-terminal peptide GPKRRQLTFRE of CENP-B isolated from cells at different cell densities (A) or upon treatment with heat shock (B), arsenite (C), or colcemid (D). Error bars represent the SEM (n=3). *, P<0.05; **, P<0.01; ***, P<0.001. The P values were calculated by using unpaired two-tailed Student’s t-test.