1. ¹Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland
2. ²Department of Oncology, Novartis Pharmaceuticals, Basel, Switzerland
3. ³CNRS UMR6061, Cell Cycle Group, University of Rennes 1, Rennes Cedex, France

Correspondence: Dr S Ferrari, Institute of Molecular Cancer Research, University of Zurich, Winterthurerstrasse 190, Zurich CH-8057, Switzerland. E-mail: sferrari@imcr.unizh.ch

Received 4 May 2005; Revised 15 July 2005; Accepted 19 July 2005; Published online 12 September 2005.

Abstract

Mitotic kinases are the ultimate target of pathways sensing genotoxic damage and impinging on the cell cycle machinery. Here, we provide evidence that Aurora A (AurA) was inhibited upon generation of double-strand breaks in DNA. We demonstrate that AurA was not downstream of CDK1 and that inhibition of AurA and CDK1 by DNA damage occurred independently. Using a cell line functionally deficient in Chk2, a selective Chk1 inhibitor and siRNA to Chk1, we show that DNA-damage signals were delivered to AurA through a Chk1-dependent pathway. With regard to the molecular mechanism of AurA inhibition, we found that the point mutation Ser₃₄₂>Ala rendered AurA resistant to inhibition by DNA damage. By means of two distinct approaches we examined the impact of reconstitution of AurA activity in DNA-damaged cells: (i) transient expression of wild-type and Ser₃₄₂>Ala mutant, but not kinase-dead, AurA led to bypass of the DNA damage block; (ii) direct transduction of highly active wt-AurA into G2 arrested cells precisely after induction of DNA damage resulted in mitotic entry. We show that the mechanism through which AurA allowed entry into mitosis was reactivation of CDK1, thus indicating that AurA plays a key role upstream of CDK1. A model depicting the possible role of AurA at the onset of mitosis and upon DNA damage is presented.