RESUMEN
Canonical Wnt/ß-catenin signaling is frequently dysregulated in myeloid leukemias and is implicated in leukemogenesis. Nuclear-localized ß-catenin is indicative of active Wnt signaling and is frequently observed in acute myeloid leukemia (AML) patients; however, some patients exhibit little or no nuclear ß-catenin even where cytosolic ß-catenin is abundant. Control of the subcellular localization of ß-catenin therefore represents an additional mechanism regulating Wnt signaling in hematopoietic cells. To investigate the factors mediating the nuclear-localization of ß-catenin, we carried out the first nuclear/cytoplasmic proteomic analysis of the ß-catenin interactome in myeloid leukemia cells and identified putative novel ß-catenin interactors. Comparison of interacting factors between Wnt-responsive cells (high nuclear ß-catenin) versus Wnt-unresponsive cells (low nuclear ß-catenin) suggested the transcriptional partner, LEF-1, could direct the nuclear-localization of ß-catenin. The relative levels of nuclear LEF-1 and ß-catenin were tightly correlated in both cell lines and in primary AML blasts. Furthermore, LEF-1 knockdown perturbed ß-catenin nuclear-localization and transcriptional activation in Wnt-responsive cells. Conversely, LEF-1 overexpression was able to promote both nuclear-localization and ß-catenin-dependent transcriptional responses in previously Wnt-unresponsive cells. This is the first ß-catenin interactome study in hematopoietic cells and reveals LEF-1 as a mediator of nuclear ß- catenin level in human myeloid leukemia.
Asunto(s)
Núcleo Celular/metabolismo , Leucemia Mieloide Aguda/metabolismo , Factor de Unión 1 al Potenciador Linfoide/metabolismo , Síndromes Mielodisplásicos/metabolismo , Proteoma/análisis , Proteína Wnt1/metabolismo , beta Catenina/metabolismo , Biomarcadores de Tumor/genética , Biomarcadores de Tumor/metabolismo , Regulación Neoplásica de la Expresión Génica , Humanos , Leucemia Mieloide Aguda/genética , Leucemia Mieloide Aguda/patología , Factor de Unión 1 al Potenciador Linfoide/antagonistas & inhibidores , Factor de Unión 1 al Potenciador Linfoide/genética , Síndromes Mielodisplásicos/patología , Dominios y Motivos de Interacción de Proteínas , ARN Interferente Pequeño/genética , Activación Transcripcional , Células Tumorales Cultivadas , Proteína Wnt1/genética , beta Catenina/genéticaRESUMEN
There are numerous forkhead transcription factors in mammalian cells but we know little about the molecular functions of the majority of these. FOXK2 is a ubiquitously expressed family member suggesting an important function across multiple cell types. Here, we show that FOXK2 binds to the SIN3A and PR-DUB complexes. The PR-DUB complex contains the important tumour suppressor protein, the deubiquitinase BAP1. FOXK2 recruits BAP1 to DNA, promotes local histone deubiquitination and causes changes in target gene activity. Our results therefore provide an important link between BAP1 and the transcription factor FOXK2 and demonstrate how BAP1 can be recruited to specific regulatory loci.
Asunto(s)
Cromatina/metabolismo , Factores de Transcripción Forkhead/metabolismo , Proteínas Supresoras de Tumor/metabolismo , Ubiquitina Tiolesterasa/metabolismo , Línea Celular , Cromatina/enzimología , Factores de Transcripción Forkhead/química , Regulación de la Expresión Génica , Genoma , Humanos , Dominios y Motivos de Interacción de Proteínas , Proteínas Represoras/metabolismo , Complejo Correpresor Histona Desacetilasa y Sin3 , Proteínas Supresoras de Tumor/química , Ubiquitina Tiolesterasa/químicaRESUMEN
The canonical Wnt signaling pathway has been the focus of intensive research because of its frequent dysregulation in human cancers. Much of this has been directed towards the aberrant expression and/or activity of the central mediator of this pathway, ß-catenin. In particular, the nuclear localization of ß-catenin and subsequent inappropriate activation of TCF/LEF-mediated transcription appears to be an important process in both the establishment and maintenance of cancer stem cells. Despite this, the exact mechanisms controlling ß-catenin nuclear localization in both normal and malignant cells are poorly understood. This prospect article brings together the many mechanisms previously reported to regulate the nuclear localization of ß-catenin and how they are relevant to cancer.