title: RAN GTPase is a RASSF1A effector involved in controlling microtubule organization.
abstract: RASSF1A is a tumor suppressor gene that is inactivated by hypermethylation of its promoter region in most types of human cancers. The incidence of spontaneous or induced tumors is significantly higher in Rassf1a(-/-) mice than in wild-type mice, confirming the tumor suppressor function of RASSF1A. RASSF1A promotes apoptosis mainly through its interaction with the proapoptotic serine/threonine STE20-like kinases MST1 and 2. However, Rassf1a(-/-) mice do not show overt signs of deregulated apoptosis, suggesting that other RASSF1A effectors are also critical for tumor suppression. In a proteomics screen, we identified RAN GTPase, MST1 and 2 kinases, and alpha- and gamma-tubulin as RASSF1A-interacting proteins. We show that RASSF1A-induced microtubule hyperstability, a hallmark of RASSF1A expression, is RAN-GTP dependent. RASSF1A promotes the accumulation of the GTP-bound form of RAN via the MST2-induced phosphorylation of RCC1. Depletion of RASSF1A results in mislocalization of RCC1 to the mitotic spindle and spindle poles, leading to mitotic spindle abnormalities and prometaphase block. A similar mitotic delay is also observed with MST2 depletion. These findings reveal a mechanism for how RASSF1A controls microtubule stability and for how its loss compromises the integrity of the mitotic spindle, leading to aneuploidy and tumorigenesis.
authors: Section of Medical and Molecular Genetics, Institute of Biomedical Research, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK. a.dallol@bham.ac.uk
authors: Ashraf
authors: A
authors: Dallol
authors: Luke B
authors: LB
authors: Hesson
authors: David
authors: D
authors: Matallanas
authors: Wendy N
authors: WN
authors: Cooper
authors: Eric
authors: E
authors: O'Neill
authors: Eamonn R
authors: ER
authors: Maher
authors: Walter
authors: W
authors: Kolch
authors: Farida
authors: F
authors: Latif
mesh_terms: D000818:Animals; D018797:Cell Cycle Proteins / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D018345:Mice, Knockout; D008856:Microscopy, Fluorescence; D008870:Microtubules / Q000378:metabolism / Q000502:physiology*; D009687:Nuclear Proteins / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D040901:Proteomics; D008941:Spindle Apparatus / Q000502:physiology*; D014404:Tubulin / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*; D020931:ran GTP-Binding Protein / Q000378:metabolism*; D000099317:Hippo Kinases
chemical_list: D018797:Cell Cycle Proteins; D020662:Guanine Nucleotide Exchange Factors; D047908:Intracellular Signaling Peptides and Proteins; D009687:Nuclear Proteins; D017346:Protein Serine-Threonine Kinases; D014404:Tubulin; D025521:Tumor Suppressor Proteins; D020931:ran GTP-Binding Protein; C120587:RAN protein, human; C411762:RASSF1 protein, human; C062521:RCC1 protein, human; C095566:STK4 protein, human; D000099317:Hippo Kinases