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Mol. Cell. Biol. doi:10.1128/MCB.00671-06
Copyright (c) 2006, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Requirement of hCenexin for proper mitotic functions of polo-like kinase 1 at the centrosomes

Laboratory of Metabolism, Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, NIH, Bethesda, MD 20892; Rexahn Pharmaceuticals, Inc., 9620 Medical Center Dr. Rockville, MD 20850, Department of Biochemistry, College of Medicine, Dankook University, Chunan, S. Korea, Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, MD 20814, Department of Biochemistry and Molecular Biology, College of Medicine, Chungbuk National University, Cheongju, S. Korea, Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, MN 55455

^* To whom correspondence should be addressed. Email: kyunglee{at}mail.nih.gov.

	Abstract

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 varient 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 kinase1 (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 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-germline cells is likely hCenexin1.

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