Differential UBE2H-CTLH E2-E3 ubiquitylation modulesregulate erythroid maturation

The developmentof haematopoietic stem cellsinto mature erythrocytes–erythropoiesis –is a controlled process characterized by cellular reorganisation and drastic reshaping of the proteome landscape.Failure of ordered erythropoiesis isassociated with anaemias and haematological malignancies. Although the ubiquitin (UB) system isa known crucial post-translational regulator in erythropoiesis, how the erythrocyteis reshaped by the UBsystemis poorly understood.Bymeasuringthe proteomiclandscape of in vitrohuman erythropoiesis models, we founddynamic differential expression ofsubunitsof the CTLH E3 ubiquitin ligase complexthat formeddistinctmaturation stage-dependent assemblies of structurally homologous RANBP9-and RANBP10-CTLH complexes.Moreover,protein abundance of CTLH’s cognate E2-conjugating enzyme UBE2H increased during terminal differentiation,which dependedon catalyticallyactive CTLH E3complexes.CRISPR-Cas9 mediated inactivation of all CTLH E3 assemblies by targeting the catalytic subunit MAEA,orUBE2H, triggered spontaneous and accelerated maturationof erythroid progenitor cellsincluding increased heme and haemoglobin synthesis. Thus, the orderly progression of human erythropoiesis is controlled by the assembly of distinct UBE2H-CTLHmodulesfunctioning at different developmental stages.