Abstract

Centrosomes organize the microtubule cytoskeleton for both interphase and mitotic functions. They are implicated in cell-cycle progression but the mechanism is unknown. Here, we show that depletion of 14 out of 15 centrosome proteins arrests human diploid cells in G1 with reduced Cdk2–cyclin A activity and that expression of a centrosome-disrupting dominant-negative construct gives similar results. Cell-cycle arrest is always accompanied by defects in centrosome structure and function (for example, duplication and primary cilia assembly). The arrest occurs from within G1, excluding contributions from mitosis and cytokinesis. The arrest requires p38, p53 and p21, and is preceded by p38-dependent activation and centrosomal recruitment of p53. p53-deficient cells fail to arrest, leading to centrosome and spindle dysfunction and aneuploidy. We propose that loss of centrosome integrity activates a checkpoint that inhibits G1–S progression. This model satisfies the definition of a checkpoint in having three elements: a perturbation that is sensed, a transducer (p53) and a receiver (p21).

1. Program in Molecular Medicine, University of Massachusetts Medical School, Worcester, Massachusetts 01605, USA.
2. National Cancer Institute, Fredrick, Maryland 21702
3. Wadsworth Center, Albany, New York 12201, USA.
4. Current address: ArQule Biomedical Institute, Inc., Norwood, Massachusetts 02062, USA.
5. These authors contributed equally to this work.

Correspondence to: Stephen Doxsey¹ e-mail: Stephen.Doxsey@umassmed.edu

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