title: DDX5 is a positive regulator of oncogenic NOTCH1 signaling in T cell acute lymphoblastic leukemia.
abstract: Notch signaling is a highly conserved cell-cell communication pathway regulating normal development and tissue homeostasis. Aberrant Notch signaling represents an important oncogenic mechanism for T cell acute lymphoblastic leukemia (T-ALL), an aggressive subset of the most common malignant childhood cancer ALL. Therefore, understanding the molecular regulation of Notch signaling is critical to identify new approaches to block aberrant Notch oncogenic activity. The family of three MAML transcriptional coactivators is crucial for Notch signaling activation. The prototypic member MAML1 is the major coactivator that regulates Notch oncogenic activities in leukemic cells. However, the molecular basis underlying MAML1 coactivator function that contributes to Notch signaling remains unclear. In this study, we performed proteomic studies and identified DDX5, an ATP-dependent DEAD-box RNA helicase, as a component of the MAML1 protein complex. DDX5 interacts with MAML1 in vitro and in vivo, and is associated with the endogenous NOTCH1 transcription activation complex in human T-ALL leukemic cells. Lentivirus-mediated short-hairpin RNA knock-down of DDX5 resulted in decreased expression of Notch target genes, reduced cell proliferation and increased apoptosis in cultured human leukemic cells with constitutive activation of Notch signaling. Also, DDX5 depletion inhibited the growth of human leukemia xenograft in nude mice. Moreover, DDX5 is highly expressed in primary human T-ALL leukemic cells based on the analyses of Oncomine and GEO databases, and Immunohistochemical staining. Our overall findings revealed a critical role of DDX5 in promoting efficient Notch-mediated transcription in leukemic cells, suggesting that DDX5 might be critical for NOTCH1-mediated T-ALL pathogenesis and thus is a potential new target for modulating the Notch signaling in leukemia.
authors.affiliation: Department of Molecular Genetics and Microbiology, Shands Cancer Center, University of Florida, Gainesville, FL, USA.
authors.forename: S
authors.initials: S
authors.lastname: Lin
authors.forename: L
authors.initials: L
authors.lastname: Tian
authors.forename: H
authors.initials: H
authors.lastname: Shen
authors.forename: Y
authors.initials: Y
authors.lastname: Gu
authors.forename: J-L
authors.initials: JL
authors.lastname: Li
authors.forename: Z
authors.initials: Z
authors.lastname: Chen
authors.forename: X
authors.initials: X
authors.lastname: Sun
authors.forename: M James
authors.initials: MJ
authors.lastname: You
authors.forename: L
authors.initials: L
authors.lastname: Wu
mesh_terms: D000818:Animals; D001483:Base Sequence; D045744:Cell Line, Tumor; D049109:Cell Proliferation; D053487:DEAD-box RNA Helicases / Q000378:metabolism / Q000502:physiology*; D017931:DNA Primers; D004268:DNA-Binding Proteins / Q000378:metabolism; D006801:Humans; D051379:Mice; D008819:Mice, Nude; D054218:Precursor T-Cell Lymphoblastic Leukemia-Lymphoma / Q000378:metabolism* / Q000473:pathology; D011485:Protein Binding; D040901:Proteomics; D060888:Real-Time Polymerase Chain Reaction; D051881:Receptor, Notch1 / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D014157:Transcription Factors / Q000378:metabolism; D023041:Xenograft Model Antitumor Assays
chemical_list: D017931:DNA Primers; D004268:DNA-Binding Proteins; C430872:MAML1 protein, human; C497761:NOTCH1 protein, human; D051881:Receptor, Notch1; D014157:Transcription Factors; C506749:Ddx5 protein, human; D053487:DEAD-box RNA Helicases