N-alpha-acetyltransferase that acetylates the N-terminus of proteins that retain their initiating methionine. Has a broad substrate specificity: able to acetylate the initiator methionine of most peptides, except for those with a proline in second position. Also displays N-epsilon-acetyltransferase activity by mediating acetylation of the side chain of specific lysines on proteins. The relevance of N-epsilon-acetyltransferase activity is however unclear. Required for sister chromatid cohesion during mitosis by promoting binding of CDCA5/sororin to cohesin