N-Alpha-Acetyltransferase 25 (NAA25)

MDM20 is a component of N-acetyltransferase complex B (NatB). Human NatB performs cotranslational N(alpha)-terminal acetylation of methionine residues when they are followed by asparagine.The deduced 972-amino acid protein has a calculated molecular mass of 112.3 kD. It has an N-terminal tetratricopeptide repeat and a putative C-terminal nuclear localization signal. MDM20 shares 20.4% and 92.9% amino acid identity with its yeast and mouse homologs, respectively. Western blot analysis detected MDM20 in all human cell lines examined. Immunofluorescence analysis of HeLa cells showed that MDM20 localized to the cytoplasm.MDM20 and NAT3 also associated with isolated HEK293 polysomes, as well as in the cytosolic fraction. Knockdown of either protein via small interfering RNA disrupted cell cycle progression.