M-Phase Phosphoprotein 9 (MPHOSPH9)

Progression of cells from interphase to mitosis involves alterations in cell structures and activities. In M phase, many proteins are phosphorylated directly by MPF or indirectly by kinases activated by MPF. These M-phase phosphoproteins (MPPs, or MPHOSPHs) permit disassembly of interphase structures and generation of M-phase enzymatic activities and structures.Immunoblot analysis showed that when phosphorylated, MPHOSPH9 is expressed as 150- and 160-kD proteins in M-phase cells. Immunofluorescence microscopy localized MPHOSPH9 to the Golgi complex in interphase, strongly overlapping with the localization of N-acetylglucosaminyltransferase I (NAGT1). However, in mitotic cells, MPHOSPH9 was dispersed throughout the cell and did not localize to the Golgi fragments containing NGAT1.