MDM2 and Aurora Kinase a Contribute to SETD2 Loss of Function in Advanced Systemic Mastocytosis: Implications for Pathogenesis and Treatment

The SETD2 gene encodes the only methyltransferase responsible for histone H3 lysine 36 trimethylation (H3K36Me3) in humans. H3K36me3 play a key role in preserving the fidelity of transcription elongation and splicing. In addition, SETD2/H3K36me3 have more recently been implicated in the maintenance of genomic integrity by regulating homologous recombination (HR) repair, Mismatch Repair (MMR) mitotic spindle assembly and chromosome segregation. SETD2 deletions and/or inactivating mutations occur in many solid tumors and have recently been found also in acute leukemias. We have reported that the HMC-1.1 and -1.2 mast cell leukemia (MCL) cell lines and many advanced systemic mastocytosis (SM) patients (pts) display H3K36Me3 deficiency as a result of non-genomic loss of function of SETD2. Proteasome inhibition restored SETD2 protein expression and H3K36me3, suggesting that a functional protein is produced but rapidly degraded. In an attempt to uncover the mechanisms underlying this phenomenon, we used an in silico approach to identify candidate SETD2-interacting proteins, followed by experimental confirmation by co-immunoprecipitation (co-IP). We found that, after proteasomal inhibition, SETD2 co-immunoprecipitates with the ubiquitin E3 ligase MDM2. Treatment with the MDM2 inhibitor SP-141 rescued SETD2 expression and H3K36Me3, suggesting that MDM2 may play a role in SETD2 degradation in ASM and MCL. Moreover, SP-141 treatment of HMC-1 cells at micromolar doses induced cytostatic...
Source: Blood - Category: Hematology Authors: Tags: 635. Myeloproliferative Syndromes: Basic Science: Poster I Source Type: research