DPY30 acts as an ASH2L-specific stabilizer to stimulate the enzyme activity of MLL family methyltransferases on different substrates

Dumpy-30 (DPY30) is a conserved component of the mixed lineage leukemia (MLL) family complex and is essential for robust methyltransferase activity of MLL complexes. However, the biochemical role of DPY30 in stimulating methyl-transferase activity of MLL complexes remains elusive. Here, we demonstrate that DPY30 plays a crucial role in regulating MLL1 activity through two com-plementary mechanisms: A nucleosome-independent mechanism and a nucleo-some-specific mechanism. DPY30 functions as an ASH2L-specific stabilizer to increase the stability of ASH2L and enhance ASH2L-mediated interactions. As a result, DPY30 promotes the compaction and stabilization of the MLL1 complex, consequently increasing the HKMT activity of the MLL1 complex on diverse sub-strates. DPY30-stabilized ASH2L further acquires additional interfaces with H3 and nucleosomal DNA, thereby boosting the methyltransferase activity of the MLL1 complex on nucleosomes. These results collectively highlight the crucial and conserved roles of DPY30 in the complex assembly and activity regulation of MLL family complexes.

Automated summary

In this study, two key mechanisms of DPY30 in regulating MLL1 activity were revealed: a nucleosome-independent mechanism and a nucleosome-specific mechanism. DPY30 stabilizes ASH2L to increase the stability and interactions of the MLL1 complex, promoting its compaction and stabilization and enhancing its activity on substrates. Additionally, DPY30-stabilized ASH2L acquires additional interfaces with H3 and nucleosomal DNA, boosting the methyltransferase activity of the MLL1 complex on nucleosomes.