title: Transcriptional intermediary factor 1γ binds to the anaphase-promoting complex/cyclosome and promotes mitosis.
abstract: The anaphase-promoting complex/cyclosome (APC/C) is an ubiquitin ligase that functions during mitosis. Here we identify the transcriptional regulator, transcriptional intermediary factor 1γ, TIF1γ, as an APC/C-interacting protein that regulates APC/C function. TIF1γ is not a substrate for APC/C-dependent ubiquitylation but instead, associates specifically with the APC/C holoenzyme and Cdc20 to affect APC/C activity and progression through mitosis. RNA interference studies indicate that TIF1γ knockdown results in a specific reduction in APC/C ubiquitin ligase activity, the stabilization of APC/C substrates, and an increase in the time taken for cells to progress through mitosis from nuclear envelope breakdown to anaphase. TIF1γ knockdown cells are also characterized by the inappropriate presence of cyclin A at metaphase, and an increase in the number of cells that fail to undergo metaphase-to-anaphase transition. Expression of a small interfering RNA-resistant TIF1γ species relieves the mitotic phenotype imposed by TIF1γ knockdown and allows for mitotic progression. Binding studies indicate that TIF1γ is also a component of the APC/C-mitotic checkpoint complex (MCC), but is not required for MCC dissociation from the APC/C once the spindle assembly checkpoint (SAC) is satisfied. TIF1γ inactivation also results in chromosome misalignment at metaphase and SAC activation; inactivation of the SAC relieves the mitotic block imposed by TIF1γ knockdown. Together these data define novel functions for TIF1γ during mitosis and suggest that a reduction in APC/C ubiquitin ligase activity promotes SAC activation.
authors.affiliation: 1] School of Cancer Sciences, College of Medical and Dental Sciences, The University of Birmingham, Edgbaston, Birmingham, UK [2] NNF Center for Protein Research, The University of Copenhagen, Blegdamsvej, Copenhagen N, Denmark.
authors.forename: G G
authors.initials: GG
authors.lastname: Sedgwick
authors.forename: K
authors.initials: K
authors.lastname: Townsend
authors.forename: A
authors.initials: A
authors.lastname: Martin
authors.forename: N J
authors.initials: NJ
authors.lastname: Shimwell
authors.forename: R J A
authors.initials: RJ
authors.lastname: Grand
authors.forename: G S
authors.initials: GS
authors.lastname: Stewart
authors.forename: J
authors.initials: J
authors.lastname: Nilsson
authors.forename: A S
authors.initials: AS
authors.lastname: Turnell
mesh_terms: D000705:Anaphase; D064173:Anaphase-Promoting Complex-Cyclosome; D064191:Apc3 Subunit, Anaphase-Promoting Complex-Cyclosome; D064199:Cdc20 Proteins; D018797:Cell Cycle Proteins / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D008024:Ligands; D059566:M Phase Cell Cycle Checkpoints; D013058:Mass Spectrometry; D018715:Microscopy, Video; D008938:Mitosis / Q000502:physiology*; D009363:Neoplasm Proteins / Q000378:metabolism; D025941:Protein Interaction Mapping; D011499:Protein Processing, Post-Translational / Q000502:physiology; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000494:pharmacology; D011993:Recombinant Fusion Proteins / Q000502:physiology; D064249:Securin; D014157:Transcription Factors / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D043743:Ubiquitin-Protein Ligase Complexes / Q000378:metabolism* / Q000502:physiology; D044767:Ubiquitin-Protein Ligases / Q000502:physiology; D054875:Ubiquitination / Q000502:physiology
chemical_list: D064191:Apc3 Subunit, Anaphase-Promoting Complex-Cyclosome; C577366:CDC27 protein, human; D064199:Cdc20 Proteins; D018797:Cell Cycle Proteins; D008024:Ligands; D009363:Neoplasm Proteins; D034741:RNA, Small Interfering; D011993:Recombinant Fusion Proteins; D064249:Securin; C511956:TRIM33 protein, human; D014157:Transcription Factors; C577488:CDC20 protein, human; D043743:Ubiquitin-Protein Ligase Complexes; D064173:Anaphase-Promoting Complex-Cyclosome; D044767:Ubiquitin-Protein Ligases