Identification of Novel α-N-Methylation of CENP-B That Regulates Its Binding to the Centromeric DNA

The eukaryotic centromere is an essential chromatin region required for accurate segregation of sister chromatids during cell division. Centromere protein B (CENP-B) is a highly conserved protein which can bind to the 17-bp CENP-B box on the centromeric DNA. In this study, we found that CENP-B could be alpha-N-methylated in human cells. We also showed that the level of the alpha-N-methylation was stimulated in cells in response to a variety of extracellular stimuli, including increased cell density, heat shock, and arsenite treatment, although the methylation level was not altered upon metaphase arrest. We identified N-terminal RCC1 methyltransferase (NRMT) as a major enzyme required for the CENP-B methylation. Additionally, we found that chromatin-bound CENP-B was primarily trimethylated and alpha-N-trimethylation could enhance CENP-B's binding to CENP-B box in cells. Our study also expands the function of protein alpha-N-methylation that has been known for decades and whose function remains largely unexplored.