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Small molecule inhibition of deubiquitinating enzyme JOSD1 as a novel targeted therapy for leukemias with mutant JAK2


Mutations in the Janus Kinase 2 (JAK2) gene resulting in constitutive kinase activation represent the most common genetic event in myeloproliferative neoplasms (MPN), a group of diseases involving overproduction of one or more kinds of blood cells, including red cells, white cells, and platelets. JAK2 kinase inhibitors, such as ruxolitinib, provide clinical benefit, but inhibition of wild-type (wt) JAK2 limits their clinical utility due to toxicity to normal cells, and small molecule inhibition of mutated JAK2 kinase activity can lead to drug resistance. Here, we present a strategy to target mutated JAK2 for degradation, using the cell’s intracellular degradation machinery, while sparing non-mutated JAK2. We employed a chemical genetics screen, followed by extensive selectivity profiling and genetic studies, to identify the deubiquitinase (DUB), JOSD1, as a novel regulator of mutant JAK2. JOSD1 interacts with and stabilizes JAK2-V617F, and inactivation of the DUB leads to JAK2-V617F protein degradation by increasing its ubiquitination levels, thereby shortening its protein half-life. Moreover, targeting of JOSD1 leads to the death of JAK2-V617F-positive primary acute myeloid leukemia (AML) cells. These studies provide a novel therapeutic approach to achieving selective targeting of mutated JAK2 signaling in MPN.

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Fig. 1: SB1-F-70 and XL-9872-106C selectively degrade JAK2-V617F and kill JAK2-V617F-expressing Ba/F3 cells.
Fig. 2: SB1-F-70 selectively degrades JAK2-V617F in human AML cells.
Fig. 3: SB1-F-70 and XL-9872-106C promote ubiquitin-mediated proteasomal degradation of JAK2-V617F in human AML cells.
Fig. 4: DUBome selectivity profiling of SB1-F-70 and XL-9872-106C.
Fig. 5: JOSD1 interacts with and stabilizes JAK2-V617F.
Fig. 6: Genetic depletion of JOSD1 selectively degrades JAK2-V617F over wt JAK2.
Fig. 7: Targeting of JOSD1 leads to JAK2-V617F-positive primary AML cell death.


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We thank Dr. Nathanael Gray for their generous provision of reagents and technical support, and Dr. Lucia Cabal-Hierro at Dana-Farber Cancer Institute—Harvard Medical School for valuable guidance for the CRISPR-CAS9 KO assay. Our work was founded by Leukemia & Lymphoma Society’s New Idea Award, Claudia Adams Barr Award, MPN Research Foundation, Gabrielle’s Angel Foundation and NIH R01 Foundation CA211681.

Author information




JY, EW and XL conceptualized, designed and performed the studies. JY, EW and XL carried out data analyses and wrote the manuscript. RM purified JOSD1 protein and performed biochemical assay for compounds testing. WC and NS performed ABPP assay for protein profiling. BH assisted with compounds designed and synthesized. SZ, IL, LD and LC-H assisted with shRNA KD/KO studies. CM helped with cell culturing and western blotting. MS provided valuable scientific feedback and guidance. JW and NG provided JAK1/JAK2 inhibitors. JAM carried out quantitative mass spectrometry. JG conceptualized and designed the studies. SB conceptualized and designed the studies, carried out data analyses and wrote the manuscript.

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Correspondence to James D. Griffin or Sara J. Buhrlage.

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Yang, J., Weisberg, E.L., Liu, X. et al. Small molecule inhibition of deubiquitinating enzyme JOSD1 as a novel targeted therapy for leukemias with mutant JAK2. Leukemia (2021).

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