UBE2O remodels the proteome during terminal erythroid differentiation

Abstract

During terminal differentiation, the global protein complement is remodeled, as epitomized by erythrocytes, whose cytosol is ~98% globin. The erythroid proteome undergoes a rapid transition at the reticulocyte stage; however, the mechanisms driving programmed elimination of preexisting cytosolic proteins are unclear. We found that a mutation in the murine Ube2o gene, which encodes a ubiquitin-conjugating enzyme induced during erythropoiesis, results in anemia. Proteomic analysis suggested that UBE2O is a broad-spectrum ubiquitinating enzyme that remodels the erythroid proteome. In particular, ribosome elimination, a hallmark of reticulocyte differentiation, was defective in Ube2o−/− mutants. UBE2O recognized ribosomal proteins and other substrates directly, targeting them to proteasomes for degradation. Thus, in reticulocytes, the induction of ubiquitinating factors may drive the transition from a complex to a simple proteome.

Regulation of GATA1 levels in erythropoiesis

“…However, perhaps counterintuitively, chemical inhibition of the proteasome in murine erythroid progenitors, or loss of the proteasome shuttle protein Rad23b, results in reduced levels of GATA1 leading to early apoptosis in vitro and to anemia in vivo, respectively . A better understanding of the action of the proteasome in erythropoiesis and how it may regulate directly or indirectly GATA1 levels, is currently the research focus of several groups …”

“…111 The role of the proteasome in erythropoiesis has been highlighted through the years, and it is well known that proteasome-inhibitor drugs used as anti-tumoral agents, especially in multiple myeloma, may cause anemia as an adverse event. [112][113][114] However, perhaps counterintuitively, chemical inhibition of the proteasome in murine erythroid progenitors, or loss of the proteasome shuttle protein Rad23b, results in reduced levels of GATA1 leading to early apoptosis in vitro and to anemia in vivo, respectively. 115 A better understanding of the action of the proteasome in erythropoiesis and how it may regulate directly or indirectly GATA1 levels, is currently the research focus of several groups.…”

“…115 A better understanding of the action of the proteasome in erythropoiesis and how it may regulate directly or indirectly GATA1 levels, is currently the research focus of several groups. 113,114,116,117 9 | THE EFFECTS OF ARTIFICIALLY ALTERING GATA1 PROTEIN LEVELS As outlined above, GATA1 translation and protein levels are exquisitely regulated in hematopoiesis and it is now well established that tinkering with GATA1 protein levels has important functional implications and may also result in hematological disease. For example, the extremes of either a complete loss of GATA1 expression or GATA1 overexpression result in both cases in embryonic lethal anemia.…”

Interconversion between Anticipatory and Active GID E3 Ubiquitin Ligase Conformations via Metabolically Driven Substrate Receptor Assembly

“…A crystal structure of peptide-bound human Gid4 showed the basis for Nterminal proline recognition (Dong et al, 2018). Although the mammalian GID E3 does not appear to regulate gluconeogenic enzymes (Lampert et al, 2018), and its N-degron substrates remain to be identified, numerous studies suggest it may also act as a central component in cell fate determination essential for some developmental pathways (Han et al, 2016;Javan et al, 2018;Liu and Pfirrmann, 2019;Nguyen et al, 2017;Pfirrmann et al, 2015;Soni et al, 2006) Here we reveal molecular mechanisms underlying assembly and activity of the largely mysterious GID E3, and provide general insight into ubiquitylation by the large cohort of terminal-degron E3s, and by those catalyzing ubiquitylation via heterodimeric RING-RING domains. Unexpectedly, our results also reveal mechanisms of stress anticipation and resolution through assembly of an E3 ligase, and that GID is not a singular complex.…”

Unc 51–like autophagy-activating kinase (ULK1) mediates clearance of free α-globin in β-thalassemia

“…In -thalassemia, unpaired -chains are polyubiquitinated and subsequently degraded by the proteasome. The erythroid-specific ubiquitin ligase UBE20 ubiquitinates free -globin (50,51), although additional ubiquitin ligases likely exist. Alternatively, free -globin (with or without a ubiquitin modification) may be eliminated by autophagy.…”