Deciphering the HDAC6-Mediated Regulation of MLLT3 in Myeloid Progenitor Cell Fate: Insights into Stem Cell Differentiation Dynamics

Mixed-lineage leukemia translocated to 3 (MLLT3) is vital for maintaining the stemness of hematopoietic stem cells. Loss of MLLT3 in megakaryocyte (MK)-erythrocyte progenitor (MEP) cells leads to its differentiation into MKs. Despite its significance in stemness, the regulatory mechanism of MLLT3 during differentiation remains elusive. In this study, we investigate the regulatory role of histone deacetylase 6 (HDAC6) in modulating MLLT3 levels via heat shock protein 90 (Hsp90) activation during myeloid lineage differentiation into MKs, monocytes, and macrophages. We found that HDAC6 activates Hsp90 through deacetylation, enabling Hsp90 to retain MLLT3 in the cytoplasm where protein kinase C (PKC) phosphorylates MLLT3 at serine residues; leading to loss of MLLT3 during MK and macrophage differentiation but not during monocyte differentiation. This research provides valuable insights into the regulatory mechanisms underlying myeloid lineage commitment and opens new avenues for future investigations into stem cell biology and therapeutic applications.