title: The Cul3/Klhdc5 E3 ligase regulates p60/katanin and is required for normal mitosis in mammalian cells.
abstract: The proper regulation of factors involved in mitosis is crucial to ensure normal cell division. Levels and activities of proteins are regulated in many ways, one of which is ubiquitin-mediated protein degradation. E3 ubiquitin ligases are involved in targeting specific substrates for degradation by facilitating their ubiquitination. In seeking to elucidate additional biological roles for Cul3 we performed a two-hybrid screen and identified Ctb9/KLHDC5 as a Cul3-interacting protein. Overexpression of Ctb9/KLHDC5 resulted in an increase in microtubule density as well as persistent microtubule bridges between post-mitotic cells. Conversely, down-regulation of Ctb9/KLHDC5 showed a pronounced reduction in microtubule density. Based on these observations, we examined the interactions between Cul3, Ctb9/KLHDC5, and the microtubule-severing protein, p60/katanin. Here we show that p60/katanin interacts with a complex consisting of Cul3 and Ctb9/KLHDC5, which results in ubiquitin laddering of p60/katanin. Also, Cul3-deficient cells or Ctb9/KLHDC5-deficient cells show an increase in p60/katanin levels, indicating that Cul3/Ctb9/KLHDC5 is required for efficient p60/katanin removal. We demonstrate a novel regulatory mechanism for p60/katanin that occurs at the level of targeted proteolysis to allow normal mitotic progression in mammalian cells.
authors.affiliation: Department of Molecular Biology, Cell Biology and Biochemistry and the Center for Genomics and Proteomics, Brown University, Providence, Rhode Island 02903, USA.
authors.forename: Cristina M
authors.initials: CM
authors.lastname: Cummings
authors.forename: Cornelia A
authors.initials: CA
authors.lastname: Bentley
authors.forename: Sarah A
authors.initials: SA
authors.lastname: Perdue
authors.forename: Peter W
authors.initials: PW
authors.lastname: Baas
authors.forename: Jeffrey D
authors.initials: JD
authors.lastname: Singer
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry / Q000502:physiology*; D000595:Amino Acid Sequence; D044842:Cullin Proteins / Q000737:chemistry / Q000502:physiology*; D005786:Gene Expression Regulation; D006367:HeLa Cells; D006801:Humans; D000074201:Katanin; D008870:Microtubules / Q000378:metabolism*; D008938:Mitosis; D008954:Models, Biological; D008969:Molecular Sequence Data; D017434:Protein Structure, Tertiary; D020798:Two-Hybrid System Techniques; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*
chemical_list: C503645:CUL3 protein, human; C503646:Cul3 protein, mouse; D044842:Cullin Proteins; D044767:Ubiquitin-Protein Ligases; D000251:Adenosine Triphosphatases; D000074201:Katanin; C541039:KLHL42 protein, human; C541038:Klhl42 protein, mouse