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Journal of Cell Science, Vol 93, 287-298, Copyright © 1989 by Company of Biologists

Submitted on January 18, 1989
Accepted on March 16, 1989

Identification of a spindle-associated protein in ciliate micronuclei

GUY KERYER 1, NICOLE GARREAU DE LOUBRESSE 2, NICOLE BORDES 1, and MICHEL BORNENS 1

1 Centre de Génétique Moléculaire, Centre National de la Recherche Scientifique, 91198, Gif/Yvette cedex, France
2 Centre de Biologie Cellulaire, Centre National de la Recherche Scientifique, 94201, Ivry/Seine, France

Author for correspondence

Ciliated protozoa display a nuclear dualism, with germinal micronuciei and a somatic macronucleus. During mitosis, which proceeds without disruption of the nuclear envelope, a spindle is organized within the micronucleus from, presumably, intranuclear microtubule-organizing centres (MTOCs). In order to characterize these MTOCs, monoclonal antibodies generated against human centrosomes were screened on several ciliates and particularly on Paramecium tetraurelia. In this ciliate, the monoclonal antibody CTR 532, which decorates centrosomal and spindle-associated components in mammalian cells, specifically labelled the micronuclei during interphase. At the electron-microscope level, it stained a fibrous material surrounding microtubules localized on the inner face of the nuclear envelope. During mitosis this decoration extended all over the metaphase spindle. At all stages of the cell cycle, the decoration remained specific to the micronucleus and was absent not only from all of the various cytoplasmic and cortical microtubule arrays but also from the macronuclei, even at early stages of their development from the zygotic nucleus. CTR 532 recognizes a single 170x103 Mr polypeptide in the cytoskeletal fraction that contains micronuclei and this polypeptide is absent in the cytoskeletal fraction of amicronucleate cells.

Key words: spindle-associated protein, micronucleus, ciliates

Submitted on January 18, 1989
Accepted on March 16, 1989






© The Company of Biologists Ltd 1989