Association of Human SCFSKP2Subunit p19SKP1with Interphase Centrosomes and Mitotic Spindle Poles

Abstract

InSaccharomyces cerevisiae,the initiation of DNA replication and mitotic progression requires SKP1p function. SKP1p is an essential subunit of a newly identified class of E3 ubiquitin protein ligases, the SCF complexes, that catalyze ubiquitin-mediated proteolysis of key cell-cycle-regulatory proteins at distinct times in the cell cycle. SKP1p is also required for proper kinetochore assembly. Little is known about the corresponding human homolog, p19SKP1, except that it is expressed throughout the cell cycle and that it too is a component of an S-phase-regulating SCF–E3 ligase complex. Here we show by immunofluorescence microscopy that p19SKP1localizes to the centrosomes. Centrosome association occurs throughout the mammalian cell cycle, including all stages of mitosis. These findings suggest that p19SKP1is a novel component of the centrosome and the mitotic spindle, which, in turn, implies a physiological role of this protein in the regulation of one or more aspects of the centrosome cycle.