CP60 - A MICROTUBULE-ASSOCIATED PROTEIN THAT IS LOCALIZED TO THE CENTROSOME IN A CELL CYCLE-SPECIFIC MANNER

DMAP190 is a microtubule-associated protein from Drosophila that is lo calized to the centrosome. In a previous study, we used affinity chrom atography to identify proteins that interact with DMAP190, and identif ied a 60-kDa protein that we named DMAP60 (Kellogg and Alberts, 1992). Like DMAP190, DMAP60 interacts with microtubules and is localized to the centrosome, and the two proteins associate as part of a multiprote in complex. We now report the cloning and sequencing of the cDNA encod ing DMAP60. The amino acid sequence of DMAP60 is not homologous to any protein in the database, although it contains six consensus sites for phosphorylation by cyclin-dependent kinases. As judged by in situ hyb ridization, the gene for DMAPGO maps to chromosomal region 46A. In agr eement with others working on Drosophila centrosomal proteins, we have changed the names for DMAP190 and DMAP60 to CP190 and CP60, respectiv ely, to give these proteins a consistent nomenclature. Antibodies that recognize CP60 reveal that it is localized to the centrosome in a cel l cycle-dependent manner. The amount of CP60 at the centrosome is maxi mal during anaphase and telophase, and then drops dramatically during late telophase or early interphase. This dramatic disappearance of CP6 0 may be due to specific proteolysis, because CP60 contains a sequence of amino acids similar to the ''destruction box'' that targets cyclin s for proteolysis at the end of mitosis. Starting with nuclear cycle 1 2, CP60 and CP190 are both found in the nucleus during interphase. CP6 0 isolated from Drosophila embryos is highly phosphorylated, and depho sphorylated CP60 is a good substrate for cyclin B/p34(cdc2) kinase com plexes. A second kinase activity capable of phosphorylating CP60 is pr esent in the CP60/CP190 multiprotein complex. We find that bacterially expressed CP60 binds to purified microtubules, and this binding is bl ocked by CP60 phosphorylation.