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Requirement of hCenexin for Proper Mitotic Functions of Polo-Like Kinase 1 at the Centrosomes ^,

Nak-Kyun Soung,^1, Young Hwi Kang,^1, Keetae Kim,² Keiju Kamijo,³ Heejeong Yoon,² Yeon-Sun Seong,⁴ Yu-Liang Kuo,⁵ Toru Miki,³ Seung R. Kim,⁶ Ryoko Kuriyama,⁷ Chou-Zen Giam,⁵ Chang H. Ahn,² and Kyung S. Lee^1*

Laboratory of Metabolism,¹ Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, Maryland 20892,³ Rexahn Pharmaceuticals, Inc., 9620 Medical Center Dr., Rockville, Maryland 20850,² Department of Biochemistry, College of Medicine, Dankook University, Chunan, South Korea,⁴ Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, Maryland 20814,⁵ Department of Biochemistry and Molecular Biology, College of Medicine, Chungbuk National University, Cheongju, South Korea,⁶ Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, Minnesota 55455⁷

Received 18 April 2006/ Returned for modification 12 June 2006/ Accepted 28 August 2006

Outer dense fiber 2 (Odf2) was initially identified as a major component of sperm tail cytoskeleton and later was suggested to be a widespread component of centrosomal scaffold that preferentially associates with the appendages of the mother centrioles in somatic cells. Here we report the identification of two Odf2-related centrosomal components, hCenexin1 and hCenexin1 variant 1, that possess a unique C-terminal extension. Our results showed that hCenexin1 is the major isoform expressed in HeLa cells, whereas hOdf2 is not detectably expressed. Mammalian polo-like kinase 1 (Plk1) is critical for proper mitotic progression, and its association with the centrosome is important for microtubule nucleation and function. Interestingly, depletion of hCenexin1 by RNA interference (RNAi) delocalized Plk1 from the centrosomes and the C-terminal extension of hCenexin1 was crucial to recruit Plk1 to the centrosomes through a direct interaction with the polo-box domain of Plk1. Consistent with these findings, the hCenexin1 RNAi cells exhibited weakened -tubulin localization and chromosome segregation defects. We propose that hCenexin1 is a critical centrosomal component whose C-terminal extension is required for proper recruitment of Plk1 and other components crucial for normal mitosis. Our results further suggest that the anti-Odf2 immunoreactive centrosomal antigen previously detected in non-germ line cells is likely hCenexin1.

Published ahead of print on 11 September 2006.

Supplemental material for this article may be found at http://mcb.asm.org/.

The first two authors contributed to this work equally.

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• Kuriyama, R., Terada, Y., Lee, K. S., Wang, C. L. C. (2007). Centrosome replication in hydroxyurea-arrested CHO cells expressing GFP-tagged centrin2. J. Cell Sci. 120: 2444-2453 [Abstract] [Full Text]