The ubiquitin ligase Triad1 inhibits myelopoiesis through UbcH7 and Ubc13 interacting domains.
Ubiquitination plays a major role in many aspects of hematopoiesis. Alterations in ubiquitination have been implicated in hematological cancer. The ubiquitin ligase Triad1 controls the proliferation of myeloid cells. Here, we show that two RING (really interesting new gene) domains in Triad1 differentially bind ubiquitin-conjugating enzymes, UbcH7 and Ubc13. UbcH7 and Ubc13 are known to catalyze the formation of different poly-ubiquitin chains. These chains mark proteins for proteasomal degradation or serve crucial non-proteolytic functions, respectively. In line with the dual Ubc interactions, we observed that Triad1 catalyzes the formation of both types of ubiquitin chains. The biological relevance of this finding was studied by testing Triad1 mutants in myeloid clonogenic assays. Full-length Triad1 and three mutants lacking conserved domains inhibited myeloid colony formation by over 50%. Strikingly, deletion of either RING finger completely abrogated the inhibitory effect of Triad1 in clonogenic growth. We conclude that Triad1 exhibits dual ubiquitin ligase activity and that both of its RING domains are crucial to inhibit myeloid cell proliferation. The differential interaction of the RINGs with Ubcs strongly suggests that the ubiquitination mediated through UbcH7 as well as Ubc13 plays a major role in myelopoiesis.
Pubmed ID: 19340006 RIS Download
Animals | Binding Sites | COS Cells | Cell Line | Cercopithecus aethiops | Humans | Kidney | Mice | Myelopoiesis | NIH 3T3 Cells | Protein Binding | Protein Interaction Mapping | Protein Processing, Post-Translational | RING Finger Domains | Recombinant Fusion Proteins | Structure-Activity Relationship | Two-Hybrid System Techniques | U937 Cells | Ubiquitin-Conjugating Enzymes | Ubiquitin-Protein Ligases | Ubiquitination