Microtubule Associated Protein 9 (MAP9)

ASAP is a microtubule-associated protein required for spindle function, mitotic progression, and cytokinesis. It contains 2 potential nuclear localization signals, 2 predicted coiled-coil domains, and a number of predicted phosphorylation sites. The deduced 647-amino acid protein has a calculated molecular mass of 75 kD.

ASAP localized to microtubules during interphase, to the mitotic spindle during mitosis, and to the central body during cytokinesis. At all phases of the cell cycle, ASAP colocalized with alpha-tubulin.ASAP overexpression in human embryonic kidney cells and osteosarcoma cells induced the formation of thick, perinuclear rings of microtubules, where ASAP colocalized with alpha-tubulin. Overexpressed ASAP stabilized microtubules against the action of a depolymerizing agent.