NRMT is an α-N-methyltransferase that methylates RCC1 and retinoblastoma protein

α-N-methylation is an unusual post-translational modification in which the amino-terminal residues of proteins are methylated. One example is the Ran guanine nucleotide-exchange factor, RCC1, which requires methylation for its association with chromatin. These authors describe the first α-N-methyltransferase, named N-terminal RCC1 methyltransferase (NRMT). They identify the NRMT recognition sequence and several new methylation targets, and demonstrate the importance of α-N-methylation for normal bipolar spindle formation and chromosome segregation.