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Fusion proteins involving Nucleoporin 98 (NUP98) are recurrently found in acute myeloid leukemia (AML) and are associated with poor prognosis. Lack of mechanistic insight into NUP98-fusion-dependent oncogenic transformation has so far precluded the development of rational targeted therapies. We reasoned that different NUP98-fusion proteins deregulate a common set of transcriptional targets that might be exploitable for therapy. To decipher transcriptional programs controlled by diverse NUP98-fusion proteins we developed mouse models for regulatable expression of NUP98/NSD1, NUP98/JARID1A and NUP98/DDX10. By integrating chromatin occupancy profiles of NUP98-fusion proteins with transcriptome profiling upon acute fusion protein inactivation in vivo, we defined the core set of direct transcriptional targets of NUP98-fusion proteins. Among those, CDK6 was highly expressed in murine and human AML samples. Loss of CDK6 severely attenuated NUP98-fusion-driven leukemogenesis and NUP98-fusion AML was sensitive to pharmacologic CDK6 inhibition in vitro and in vivo. These findings identify CDK6 as a conserved, critical direct target of NUP98-fusion proteins, proposing CDK4/CDK6 inhibitors as a new rational treatment option for AML patients with NUP98-fusions.

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NUP98-fusion proteins cause acute myeloid leukemia via unknown molecular mechanisms. All NUP98-fusion proteins share an intrinsically disordered region (IDR) featuring >35 repeats of Phenylalanine-Glycine (FG) in the NUP98 N-terminus. Conversely, different C-terminal NUP98-fusion partners are often transcriptional and epigenetic regulators. Given these structural features we hypothesized that mechanisms of oncogenic transformation by NUP98-fusion proteins are hard-wired in their protein interactomes. Affinity purification coupled to mass spectrometry of five distinct NUP98-fusion proteins revealed a conserved set of interactors that was highly enriched for proteins involved in biomolecular condensation. We developed biotinylated isoxazole-mediated condensome mass spectrometry (biCon-MS) to show that NUP98-fusion proteins alter the global composition of biomolecular condensates. In addition, an artificial FG-repeat containing fusion protein was able to phenocopy the induction of leukemic gene expression as mediated by NUP98-KDM5A. Thus, we propose that IDR-containing fusion proteins have evolved to uniquely combine biomolecular condensation with gene control to induce cancer.AML, NUP98, fusion protein, AP-MS, LLPS, biCon-MS, condensate

C r i b b s e t a l 2 SIGNIFICANCE STATEMENTThe precise regulation of Th17 cell metabolic function is central to an inflammatory response.Following activation, T cells undergo metabolic reprogramming and utilise up-regulated glycolysis to increase the availability of ATP. This work establishes an epigenetic link between the H3K27 demethylases KDM6A/B and the coordination of a metabolic response in activated Th17 cells.Inhibition of KDM6A/B leads to global increases in the repressive H3K27me3 histone mark resulting in down-regulation of key transcription factors, followed by metabolic reprogramming and the induction of anergy in Th17 cells. This work suggests a critical role of KDM6 enzymes in maintaining Th17 functions by controlling metabolic switches, necessary for T cells to adapt to their specific roles. C r i b b s e t a l 3 ABSTRACT T helper (T h ) cells are CD4+ effector T cells that play an instrumental role in immunity by shaping the inflammatory cytokine environment in a variety of physiological and pathological situations. Using a combined chemico-genetic approach we identify histone H3K27 demethylases KDM6A and KDM6B as central regulators of human Th subsets. The prototypic KDM6 inhibitor GSK-J4 increases genome-wide levels of the repressive H3K27me3 chromatin mark and leads to suppression of the key transcription factor RORγt during Th17 differentiation, whereas in mature Th17 cells an altered transcriptional program leads to a profound metabolic reprogramming with concomitant suppression of IL-17 cytokine levels and reduced proliferation. Single cell analysis reveals a specific shift from highly inflammatory cell subsets towards a resting state upon demethylase inhibition. The apparent root cause of the observed anti-inflammatory phenotype in stimulated Th17 cells is reduced expression of key metabolic transcription factors, such as PPRC1 and c-myc. Overall, this leads to reduced mitochondrial biogenesis resulting in a metabolic switch with concomitant anti-inflammatory effects. These data are consistent with an opposing effect of GSK-J4 on Th17 T-cell differentiation pathways directly related to proliferation and effector cytokine profiles.

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