Intrinsically disordered sequence in the ZMIZ1 drives leukemic activity, regulates protein stability and biomolecular condensate formation 2253537

Abstract Introduction T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive blood cancer in children and adults, marked by the uncontrolled growth of immature T cells infiltrating the bone marrow, with frequent peripheral blood, mediastinal, and central nervous system involvement. Our lab found that Zinc Finger MIZ-containing 1 (ZMIZ1), a transcription cofactor in the PIAS-like family, drives NOTCH1-mutated and early precursor T-ALL. ZMIZ1 binds various transcription factors, influencing development and disease. We identified somatic mutations in the alanine-rich domain (ARD) of ZMIZ1 in T-ALL patients and found these mutations are mutually exclusive with germline ARD mutations seen in neurodevelopmental disorder (NEDDFSA). The ARD’s function is unknown. Methods We aim to uncover ARD’s role in T-ALL by studying these mutations. We cloned WT and mutant ZMIZ1 into retroviruses and transduced them into ZMIZ1-deficient 8946 T-ALL cells. Results T-ALL mutants showed increased ZMIZ1 protein levels compared to WT, while a NEDDFSA mutant showed decreased levels, with mRNA unchanged, indicating effects on protein stability. Deleting ARD (ΔARD) raised ZMIZ1 abundance 2.5-fold, suggesting ARD acts as a degron; cycloheximide treatment supported higher stability in ΔARD cells. Preliminary data link ARD mutations to faster cell growth versus WT. To further study ARD, we made GFP-ARD chimeras with T-ALL and NEDDFSA mutations, finding T-ALL mutants had higher expression than NEDDFSA ones. Proteasome inhibition increased GFP-ARD levels, indicating ARD-induced degradation is proteasome-dependent. Our data suggest adjacent ARD mutations can either drive T-ALL or neurodevelopmental disorders by affecting ZMIZ1 stability. Conclusion Understanding ARD regulation of ZMIZ1 may open therapies for ZMIZ1-dependent cancers, as these mutations also appear in brain, breast, B-cell, and myeloid cancers. Funding Source Post-Doctoral Fellowship NIH NIGMS K12 GM 111725 Topic Categories Hematopoiesis and Immune System Development (HEM)