title: Preferential interaction of TIP120A with Cul1 that is not modified by NEDD8 and not associated with Skp1.
abstract: The SCF complex, which consists of the invariable components Skp1, Cul1, and Rbx1 as well as a variable F-box protein, functions as an E3 ubiquitin ligase. The mechanism by which the activity of this complex is regulated, however, has been unclear. The application of tandem affinity purification has now resulted in the identification of a novel Cul1-binding protein: TATA-binding protein-interacting protein 120A (TIP120A, also called CAND1). Immunoprecipitation, immunoblot, and immunofluorescence analyses with mammalian cells revealed that TIP120A physically associates with Cul1 in the nucleus and that this interaction is mediated by a central region of Cul1 distinct from its binding sites for Skp1 and Rbx1. Furthermore, TIP120A was shown to interact selectively with Cul1 that is not modified by NEDD8. The Cul1-TIP120A complex does not include Skp1, raising the possibility that TIP120A competes with Skp1 for binding to Cul1. These observations thus suggest that TIP120A may function as a negative regulator of the SCF complex by binding to nonneddylated Cul1 and thereby preventing assembly of this ubiquitin ligase.
authors.affiliation: Department of Molecular and Cellular Biology, Medical Institute of Bioregulation, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka, Japan.
authors.forename: Kiyotaka
authors.initials: K
authors.lastname: Oshikawa
authors.forename: Masaki
authors.initials: M
authors.lastname: Matsumoto
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Yada
authors.forename: Takumi
authors.initials: T
authors.lastname: Kamura
authors.forename: Shigetsugu
authors.initials: S
authors.lastname: Hatakeyama
authors.forename: Keiichi I
authors.initials: KI
authors.lastname: Nakayama
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000378:metabolism*; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D044842:Cullin Proteins; D006367:HeLa Cells; D006801:Humans; D008025:Ligases / Q000378:metabolism*; D046911:Macromolecular Substances; D008954:Models, Biological; D000075687:NEDD8 Protein; D044786:S-Phase Kinase-Associated Proteins; D014157:Transcription Factors; D014452:Ubiquitins / Q000378:metabolism*
chemical_list: C486317:CAND1 protein, human; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; C100318:Cullin 1; D044842:Cullin Proteins; D046911:Macromolecular Substances; D000075687:NEDD8 Protein; C082860:NEDD8 protein, human; D044786:S-Phase Kinase-Associated Proteins; D014157:Transcription Factors; D014452:Ubiquitins; D008025:Ligases