Phosphorylation and Stabilization of HURP by Aurora-A: Implication of HURP as a Transforming Target of Aurora-A

Abstract

Aurora-A, a mitotic serine/threonine kinase with oncogene characteristics, has recently drawn intense attention because of its association with the development of human cancers and its relationship with mitotic progression. Using the gene expression profiles of Aurora-A as a template to search for and compare transcriptome expression profiles in publicly accessible microarray data sets, we identified HURP (encodes hepatoma upregulated protein) as one of the best Aurora-A-correlated genes. Empirical validation indicates that HURP has several characteristics in common with Aurora-A. These two genes have similar expression patterns in hepatocellular carcinoma, liver regeneration after partial hepatectomy, and cell cycle progression and across a variety of tissues and cell lines. Moreover, Aurora-A phosphorylated HURP in vitro and in vivo. Ectopic expression of either the catalytically inactive form of Aurora-A or the HURP-4P mutant, in which the Aurora-A phosphorylation sites were replaced with Ala, resulted in HURP instability and complex disassembly. In addition, HURP-wild-type stable transfectants were capable of growing in low-serum environments whereas HURP-4P grew poorly under low-serum conditions and failed to proliferate. These studies together support the view that the ability to integrate evidence derived from microarray studies into biochemical analyses may ultimately augment our predictive power when analyzing the potential role of poorly characterized proteins. While this combined approach was simply an initial attempt to answer a range of complex biological questions, our findings do suggest that HURP is a potential oncogenic target of Aurora-A.

ACKNOWLEDGMENTS

We thank Erich A. Nigg for providing Aurora-A and Aurora-B cDNAs and Tang K. Tang for providing recombinant Aurora-C protein. We are also grateful to Hau-Chen Lin and Ming-Hong Lin for technical assistance and Yeou-Guang Tsay for LC MS/MS analysis.

This work was supported in part by grants from the National Health Research Institutes, the Taichung Veteran General Hospital (TCVGH-927312D), and the National Science Council (NRPGM: NHRI93A1-NSCMM-11-5) to C. F. Huang and a grant from the National Health Research Institutes (NHRI-EX90-9001-BL) to C. K. Chou.