Direct inhibition of transcription factor complexes remains a central challenge in the discipline of ligand discovery. In general, these proteins lack surface involutions suitable for high-affinity binding by small molecules. Here we report the design of synthetic, cell-permeable, stabilized α-helical peptides that target a critical protein-protein interface in the NOTCH transactivation complex. We demonstrate that direct, high-affinity binding of the hydrocarbon-stapled peptide SAHM1 prevents assembly of the active transcriptional complex. Inappropriate NOTCH activation is directly implicated in the pathogenesis of several disease states, including T-cell acute lymphoblastic leukaemia (T-ALL). The treatment of leukaemic cells with SAHM1 results in genome-wide suppression of NOTCH-activated genes. Direct antagonism of the NOTCH transcriptional program ©2009 Macmillan Publishers Limited. All rights reservedCorrespondence and requests for materials should be addressed to J.E.B. (james_bradner@dfci.harvard.edu) or G.L.V. (gregory_verdine@harvard.edu). Full Methods and any associated references are available in the online version of the paper at www.nature.com/nature.Supplementary Information is linked to the online version of the paper at www.nature.com/nature. Author Contributions R.E.M., G.L.V. and J.E.B. conceptualized the study, designed the experiments, interpreted data, and wrote the manuscript. Design, synthesis and biological characterization of SAHM peptides was performed by R.E.M. C.D.B., J.C.A. and S.C.B. contributed key reagents and analysed data. R.E.M., M.C., T.N.D., J.C.A., A.L.K., D.G.G. and J.E.B. established the bioluminescent T-ALL model, designed and performed in vivo experiments and analysed data.Author Information All microarray data has been deposited to the Gene Expression Omnibus at the National Center for Biotechnology Information under accession numbers GSE18198 and GSE18351. Reprints and permissions information is available at www.nature.com/reprints. The authors declare competing financial interests: details accompany the full-text HTML version of the paper at www.nature.com/nature. NIH Public Access Author ManuscriptNature. Author manuscript; available in PMC 2010 October 7. Ligand binding to the extracellular domain of NOTCH1 initiates sequential proteolytic processing events catalysed respectively by an ADAM family metalloprotease and a γ-secretase complex, resulting in cytoplasmic release of the intracellular domain of NOTCH1 (ICN1)4 -6. ICN1 then translocates to the nucleus and loads onto the DNA-bound transcription factor CSL7. The engagement of ICN1 with CSL creates a long, shallow groove along the interface of the two proteins that serves as a binding surface for coactivator proteins of the mastermind-like (MAML) family8 , 9. The resulting ICN-CSL-MAML ternary complex then recruits the core transcription machinery, effecting activation of NOTCH-dependent target genes.The duration and strength of NOTCH signalling is normally tightly controlled. Whereas lossof-function mut...

Summary Cancer cells neutralize p53 by deletion, mutation, proteasomal degradation, or sequestration to achieve a pathologic survival advantage. Targeting the E3 ubiquitin ligase HDM2 can lead to a therapeutic surge in p53 levels. However, the efficacy of HDM2 inhibition can be compromised by overexpression of HDMX, an HDM2 homologue that binds and sequesters p53. Here we report that a stapled p53 helix preferentially targets HDMX, blocks the formation of inhibitory p53-HDMX complexes, induces p53-dependent transcriptional upregulation, and thereby overcomes HDMX-mediated cancer resistance in vitro and in vivo. Importantly, our analysis of p53 interaction dynamics provides a blueprint for reactivating the p53 pathway in cancer by matching HDM2, HDMX, or dual inhibitors to the appropriate cellular context.

Leukemias that harbor translocations involving the mixed lineage leukemia gene (MLL) possess unique biologic characteristics and often have an unfavorable prognosis. Gene expression analyses demonstrate a distinct profile for MLL-rearranged leukemias with consistent high-level expression of select Homeobox genes, including HOXA9. Here, we investigated the effects of HOXA9 suppression in MLLrearranged and MLL-germline leukemias using RNA interference. Gene expression profiling after HOXA9 suppression demonstrated co-down-regulation of a program highly expressed in human MLL-AML and murine MLL-leukemia stem cells, including HOXA10, MEIS1, PBX3, and MEF2C. We demonstrate that HOXA9 depletion in 17 human AML/ALL cell lines (7 MLL-rearranged, 10 MLL-germline) induces proliferation arrest and apoptosis specifically in MLL-rearranged cells (P ‫؍‬ . IntroductionTranslocations involving the mixed lineage leukemia locus (MLL, All-1, HRX) on chromosome 11q23 are found in a variety of hematologic malignancies, including acute myeloid leukemias (AMLs), B-precursor and T-lineage acute lymphoblastic leukemias, and myelodysplastic syndrome. MLL rearrangements are present in most infant leukemias [1][2][3][4] and in secondary leukemias after treatment with topoisomerase inhibitors. [5][6][7][8] Infants diagnosed with lymphoblastic leukemia harboring a MLL translocation respond poorly to current chemotherapy regimens and have a particularly unfavorable prognosis with an overall survival of less than 50%. [9][10][11][12][13] The pathophysiologic mechanisms by which MLL translocations cause leukemia and the genes that serve as critical downstream targets during induction and maintenance of the leukemic phenotype are incompletely characterized. Gene expression profiling in human acute myeloid and lymphoblastic leukemias demonstrated a characteristic gene expression pattern for cases with MLL rearrangements [14][15][16] that may be driven by unique histone methylation programs. [17][18][19][20] A common unifying feature in myeloid and lymphoid leukemias with MLL rearrangements is high-level expression of Homeobox (HOX) genes with a particular emphasis on the 5Ј-HOXA genes (HOXA5-11). [14][15][16]21,22 Elevated expression of certain 5Ј-HoxA cluster genes is also found in murine leukemia models after introduction of various leukemia-associated Mll-fusion proteins. [23][24][25][26][27] In a recent murine retroviral transduction/transplantation study, we determined the gene expression profile of leukemia stem cells that were initiated by expression of Mll-Af9 in committed granulocyte macrophage progenitors (GMPs). 28 5Ј-HoxA cluster genes HoxA5, HoxA10, and in particular HoxA9 were prominent members of a gene expression signature found in leukemia stem cells and were immediately induced after Mll-Af9 expression. 28 These findings support a hierarchical model of leukemia initiation by the MLL-AF9 fusion where certain HOXA cluster genes belong to a crucial subset of proximate target genes, which are immediately activated by MLL-AF9 express...

Background and Purpose-The purpose of this study was to assess the efficacy of neuromuscular stimulation in enhancing the upper extremity motor and functional recovery of acute stroke survivors. Methods-Forty-six stroke survivors admitted to an inpatient rehabilitation unit were randomly assigned to receive either neuromuscular stimulation or placebo. Twenty-eight subjects completed the study. The treatment group received surface neuromuscular stimulation to produce wrist and finger extension exercises. The control group received placebo stimulation over the paretic forearm. All subjects were treated 1 hour per day, for a total of 15 sessions. Outcomes were assessed in a blinded manner with the upper extremity component of the Fugl-Meyer Motor Assessment and the self-care component of the Functional Independence Measure at pretreatment, after treatment, and at 4 and 12 weeks after treatment. Results-The treatment subjects and control subjects had comparable baseline characteristics. Parametric analyses revealed significantly greater gains in Fugl-Meyer scores for the treatment group after treatment (13.1 versus 6.5; Pϭ0.05), at 4 weeks after treatment (17.9 versus 9.7; Pϭ0.05), and at 12 weeks after treatment (20.6 versus 11.2; Pϭ0.06).Functional Independence Measure scores were not different between groups at any of the time periods (PϾ0.10). Conclusions-Data suggest that neuromuscular stimulation enhances the upper extremity motor recovery of acute stroke survivors. However, the sample size in this study was too small to detect any significant effect of neuromuscular stimulation on self-care function. (Stroke. 1998;29:975-979.)