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Expression profiling of fresh, DMSO or UM171 expanded CD34+ cells by high throughput sequencing

ABSTRACT: Ex-vivo expansion of hematopoietic stem cells (HSCs) is gaining in importance for cell and gene therapy and requires a shift from dormancy state to activation and cycling. However, abnormal or excessive HSC activation results in reduced self-renewal ability and increased propensity for myeloid-biased differentiation. To date, the threshold of HSC activation that marks “the point of no return” is undetermined. Identifying the molecular determinants that restrain or control HSC activation is essential for preventing accelerated exhaustion of cultured-HSCs. We now report that activation of the E3 ligase complex CRL3KBTBD4 by UM171 not only induces epigenetic changes through CoREST1 degradation but also control chromatin bound MYC levels to prevent excessive activation and maintain lympho-myeloid potential of expanded populations. Furthermore, reconstitution activity and multipotency of UM171-treated HSC is specifically compromised when MYC levels are experimentally increased despite degradation of CoREST1.

ORGANISM(S): Homo sapiens

PROVIDER: GSE232227 | GEO | 2024/10/24

REPOSITORIES: GEO

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Project description:UM171 is a potent small molecule agonist of ex vivo human hematopoietic stem cell (HSC) self-renewal, a process that is tightly controlled by epigenetic regulation. By co opting KBTBD4, a substrate receptor of the CULLIN3-RING E3 ubiquitin ligase complex, UM171 promotes the degradation of members of the CoREST transcriptional corepressor complex, thereby limiting HSC attrition. However, the direct target and mechanism of action of UM171 remain unclear. Here, we reveal that UM171 acts as a molecular glue to induce high-affinity interactions between KBTBD4 and HDAC1/2 to promote the degradation of select corepressor complexes. Through proteomics and chemical inhibitor studies, we discover that the principal target of UM171 is HDAC1/2. Cryo-electron microscopy (cryo-EM) analysis of dimeric KBTBD4 bound to UM171 and the LSD1-HDAC1-CoREST complex unveils an unexpected asymmetric assembly, in which a single UM171 molecule enables a pair of KELCH-repeat propeller domains from the structurally plastic KBTBD4 dimer to recruit HDAC1 by clamping on its catalytic domain. One of the KBTBD4 propellers partially masks the rim of the HDAC1 active site pocket, which is exploited by UM171 to extend the E3-neo-substrate interface. The other propeller cooperatively strengthens HDAC1 binding via a separate and distinct interface. The overall neomorphic interaction is further buttressed by an endogenous cofactor of HDAC1-CoREST, inositol hexakisphosphate, which makes direct contacts with KBTBD4 and acts as a second molecular glue. The functional relevance of the quaternary complex interaction surfaces defined by cryo-EM is demonstrated by in situ base editor scanning of KBTBD4 and HDAC1. By delineating the direct target of UM171 and its mechanism of action, our results reveal how the cooperativity offered by a large dimeric CRL E3 family can be leveraged by a small molecule degrader and establish for the first time a dual molecular glue paradigm.

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Expression profiling of fresh, DMSO or UM171 expanded CD34+ cells by high throughput sequencing

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