title: A new mode of DNA binding distinguishes Capicua from other HMG-box factors and explains its mutation patterns in cancer.
abstract: HMG-box proteins, including Sox/SRY (Sox) and TCF/LEF1 (TCF) family members, bind DNA via their HMG-box. This binding, however, is relatively weak and both Sox and TCF factors employ distinct mechanisms for enhancing their affinity and specificity for DNA. Here we report that Capicua (CIC), an HMG-box transcriptional repressor involved in Ras/MAPK signaling and cancer progression, employs an additional distinct mode of DNA binding that enables selective recognition of its targets. We find that, contrary to previous assumptions, the HMG-box of CIC does not bind DNA alone but instead requires a distant motif (referred to as C1) present at the C-terminus of all CIC proteins. The HMG-box and C1 domains are both necessary for binding specific TGAATGAA-like sites, do not function via dimerization, and are active in the absence of cofactors, suggesting that they form a bipartite structure for sequence-specific binding to DNA. We demonstrate that this binding mechanism operates throughout Drosophila development and in human cells, ensuring specific regulation of multiple CIC targets. It thus appears that HMG-box proteins generally depend on auxiliary DNA binding mechanisms for regulating their appropriate genomic targets, but that each sub-family has evolved unique strategies for this purpose. Finally, the key role of C1 in DNA binding also explains the fact that this domain is a hotspot for inactivating mutations in oligodendroglioma and other tumors, while being preserved in oncogenic CIC-DUX4 fusion chimeras associated to Ewing-like sarcomas.
authors.affiliation: Institut de Biologia Molecular de Barcelona-CSIC, Barcelona, Spain.
authors.forename: Marta
authors.initials: M
authors.lastname: Forés
authors.affiliation: Molecular Oncology Programme, Centro Nacional de Investigaciones Oncológicas, Madrid, Spain.
authors.forename: Lucía
authors.identifier: 0000-0002-3281-8144
authors.initials: L
authors.lastname: Simón-Carrasco
authors.affiliation: Institut de Biologia Molecular de Barcelona-CSIC, Barcelona, Spain.
authors.forename: Leiore
authors.identifier: 0000-0001-5375-3370
authors.initials: L
authors.lastname: Ajuria
authors.affiliation: Institut de Biologia Molecular de Barcelona-CSIC, Barcelona, Spain.
authors.forename: Núria
authors.initials: N
authors.lastname: Samper
authors.affiliation: Institut de Biologia Molecular de Barcelona-CSIC, Barcelona, Spain.
authors.forename: Sergio
authors.identifier: 0000-0002-4845-6969
authors.initials: S
authors.lastname: González-Crespo
authors.affiliation: Molecular Oncology Programme, Centro Nacional de Investigaciones Oncológicas, Madrid, Spain.
authors.forename: Matthias
authors.identifier: 0000-0002-3205-456X
authors.initials: M
authors.lastname: Drosten
authors.affiliation: Molecular Oncology Programme, Centro Nacional de Investigaciones Oncológicas, Madrid, Spain.
authors.forename: Mariano
authors.initials: M
authors.lastname: Barbacid
authors.affiliation: Institut de Biologia Molecular de Barcelona-CSIC, Barcelona, Spain.|ICREA, Barcelona, Spain.
authors.forename: Gerardo
authors.identifier: 0000-0003-2765-9289
authors.initials: G
authors.lastname: Jiménez
mesh_terms: D020816:Amino Acid Motifs / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D030801:Animals, Genetically Modified; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D004247:DNA / Q000235:genetics* / Q000378:metabolism; D004330:Drosophila / Q000196:embryology / Q000235:genetics / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D057809:HEK293 Cells; D024742:HMG-Box Domains / Q000235:genetics; D024002:HMGB Proteins / Q000235:genetics* / Q000378:metabolism; D006609:High Mobility Group Proteins / Q000235:genetics* / Q000378:metabolism; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D018613:Microscopy, Confocal; D008957:Models, Genetic; D009154:Mutation; D009369:Neoplasms / Q000235:genetics* / Q000378:metabolism; D011485:Protein Binding; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid
chemical_list: C121257:DUX4L1 protein, human; D029721:Drosophila Proteins; D024002:HMGB Proteins; D006609:High Mobility Group Proteins; D018398:Homeodomain Proteins; D012097:Repressor Proteins; C404284:cic protein, Drosophila; D004247:DNA