Monoclonal antibody against the centrosome

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Abstract
A monoclonal antibody, MPM-13, raised against mitotic HeLa cell extracts recognized a perinuclear area in interphase cells and spindle poles in mitotic cells of human, mouse, Chinese hamster and sea urchin. On immunoblots MPM-13 recognized a major protein band at 43×103Mr and a variable minor band at 56 ×103Mr in both mitotic and interphase HeLa cells. These antigens were detectable in a variety of mammalian cells as well as in the unicellular ciliate Tetrahymena. In cells arrested in mitosis by colcemid and stained with MPM-13 by indirect immunofluorescence, numerous fluorescent speckles were seen throughout the cytoplasm. Reversal of colcemid block in Chinese hamster ovary (CHO) cells by washing resulted in the reappearance of a fluorescent patch at the poles of the re-formed spindles. In HeLa cells arrested in mitosis by the microtubule stabilizing drug taxol, MPM-13 stained a large fluorescent patch encircled by dark metaphase chromosomes. This pattern indicated the failure of centrioles to move to the opposite poles in the presence of taxol. These data indicate that the MPM-13 antigens are associated with the colcemid-sensitive pericentriolar material from which microtubules originate but not with the centrioles themselves. It is also clear that these antigens are highly conserved during evolution.