Mapping to chromosome 21, the FASP1 gene (FAPP1-associated protein 1) encodes a 233 amino acid protein that is homologous to the fission yeast protein Mis18. In yeast, Mis18 is localized to the centrosome and forms a complex with Mis16 to maintain the deacetylated state of histones specifically in the central core of centromeres. FASP1, also known as Protein Mis18-alpha and C21orf45, is required for the recruitment of CENP-A to centrosomes and is thereby essential for normal chromosome segregation during mitosis. With expression in testis, FASP1 exists as a homodimer, a heterodimer with MIS18B or is present in a complex containing other Mis18 family members. FASP1 has been shown to bind to pp5644 in Hela cells, where overexpression of pp5644 leads to inhibited growth and colony formation.