title: RASSF1C, an isoform of the tumor suppressor RASSF1A, promotes the accumulation of beta-catenin by interacting with betaTrCP.
abstract: The Ras-association domain family 1 (RASSF1) gene has seven different isoforms; isoform A is a tumor-suppressor gene (RASSF1A). The promoter of RASSF1A is inactivated in many cancers, whereas the expression of another major isoform, RASSF1C, is not affected. Here, we show that RASSF1C, but not RASSF1A, interacts with betaTrCP. Binding of RASSF1C to betaTrCP involves serine 18 and serine 19 of the SS(18)GYXS(19) motif present in RASSF1C but not in RASSF1A. This motif is reminiscent of the canonical phosphorylation motif recognized by betaTrCP; however, surprisingly, the association between RASSF1C and betaTrCP does not occur via the betaTrCP substrate binding domain, the WD40 repeats. Overexpression of RASSF1C, but not of RASSF1A, resulted in accumulation and transcriptional activation of the beta-catenin oncogene, due to inhibition of its betaTrCP-mediated degradation. Silencing of RASSF1A by small interfering RNA was sufficient for beta-catenin to accumulate, whereas silencing of both RASSF1A and RASSF1C had no effect. Thus, RASSF1A and RASSF1C have opposite effects on beta-catenin degradation. Our results suggest that RASSF1C expression in the absence of RASSF1A could play a role in tumorigenesis.
authors.affiliation: Institut Cochin, Département Maladies Infectieuses; Institut National de la Sante et de la Recherche Medicale U567, 27 rue du Faubourg Saint-Jacques, Bâtiment G Roussy, 75014 Paris, France.
authors.forename: Emilie
authors.initials: E
authors.lastname: Estrabaud
authors.forename: Irina
authors.initials: I
authors.lastname: Lassot
authors.forename: Guillaume
authors.initials: G
authors.lastname: Blot
authors.forename: Erwann
authors.initials: E
authors.lastname: Le Rouzic
authors.forename: Valérie
authors.initials: V
authors.lastname: Tanchou
authors.forename: Eric
authors.initials: E
authors.lastname: Quemeneur
authors.forename: Laurent
authors.initials: L
authors.lastname: Daviet
authors.forename: Florence
authors.initials: F
authors.lastname: Margottin-Goguet
authors.forename: Richard
authors.initials: R
authors.lastname: Benarous
mesh_terms: D020816:Amino Acid Motifs; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D020868:Gene Silencing; D006367:HeLa Cells; D006801:Humans; D011485:Protein Binding; D034741:RNA, Small Interfering / Q000235:genetics; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*; D051176:beta Catenin / Q000037:antagonists & inhibitors / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D044844:beta-Transducin Repeat-Containing Proteins / Q000378:metabolism*
chemical_list: C471644:BTRC protein, human; C411762:RASSF1 protein, human; D034741:RNA, Small Interfering; D025521:Tumor Suppressor Proteins; D051176:beta Catenin; D044844:beta-Transducin Repeat-Containing Proteins