title: Notch signaling induces SKP2 expression and promotes reduction of p27Kip1 in T-cell acute lymphoblastic leukemia cell lines.
abstract: In T-cell acute lymphoblastic leukemia (T-ALL) NOTCH 1 receptors are frequently mutated. This leads to aberrantly high Notch signaling, but how this translates into deregulated cell cycle control and the transformed cell type is poorly understood. In this report, we analyze downstream responses resulting from the high level of NOTCH 1 signaling in T-ALL. Notch activity, measured immediately downstream of the NOTCH 1 receptor, is high, but expression of the canonical downstream Notch response genes HES 1 and HEY 2 is low both in primary cells from T-ALL patients and in T-ALL cell lines. This suggests that other immediate Notch downstream genes are activated, and we found that Notch signaling controls the levels of expression of the E3 ubiquitin ligase SKP2 and its target protein p27Kip1. We show that in T-ALL cell lines, recruitment of NOTCH 1 intracellular domain (ICD) to the SKP2 promoter was accompanied by high SKP2 and low p27Kip1 protein levels. In contrast, pharmacologically blocking Notch signaling reversed this situation and led to loss of NOTCH 1 ICD occupancy of the SKP2 promoter, decreased SKP2 and increased p27Kip1 expression. T-ALL cells show a rapid G1-S cell cycle transition, while blocked Notch signaling resulted in G0/G1 cell cycle arrest, also observed by transfection of p27Kip1 or, to a smaller extent, a dominant negative SKP2 allele. Collectively, our data suggest that the aberrantly high Notch signaling in T-ALL maintains SKP2 at a high level and reduces p27Kip1, leading to more rapid cell cycle progression.
authors.affiliation: Department of Cell and Molecular Biology, Medical Nobel Institute, Karolinska, Institute, von Eulers väg 3, SE-171 77 Stockholm, Sweden.
authors.forename: Takeaki
authors.initials: T
authors.lastname: Dohda
authors.forename: Aljona
authors.initials: A
authors.lastname: Maljukova
authors.forename: Lining
authors.initials: L
authors.lastname: Liu
authors.forename: Mats
authors.initials: M
authors.lastname: Heyman
authors.forename: Dan
authors.initials: D
authors.lastname: Grandér
authors.forename: David
authors.initials: D
authors.lastname: Brodin
authors.forename: Olle
authors.initials: O
authors.lastname: Sangfelt
authors.forename: Urban
authors.initials: U
authors.lastname: Lendahl
mesh_terms: D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism; D002453:Cell Cycle / Q000502:physiology; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D002648:Child; D050760:Cyclin-Dependent Kinase Inhibitor p27; D020869:Gene Expression Profiling; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D054198:Precursor Cell Lymphoblastic Leukemia-Lymphoma / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D051881:Receptor, Notch1 / Q000235:genetics / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D044786:S-Phase Kinase-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D013601:T-Lymphocytes / Q000166:cytology / Q000378:metabolism*
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D018797:Cell Cycle Proteins; D050760:Cyclin-Dependent Kinase Inhibitor p27; D047908:Intracellular Signaling Peptides and Proteins; D051881:Receptor, Notch1; D012097:Repressor Proteins; D044786:S-Phase Kinase-Associated Proteins; C436291:CDKN1B protein, human; C485631:HEY1 protein, human; C405693:HEY2 protein, human; C497761:NOTCH1 protein, human