6dc0
Tribbles (TRIB1) pseudokinase fused to CCAAT-enhancer binding protein (C/EBPalpha) degron
Structural highlights
DiseaseCEBPA_HUMAN Acute myeloid leukemia with CEBPA somatic mutations;Acute myeloid leukemia with t(8;21)(q22;q22) translocation;Inherited acute myeloid leukemia. The disease is caused by variants affecting the gene represented in this entry. FunctionCEBPA_HUMAN Transcription factor that coordinates proliferation arrest and the differentiation of myeloid progenitors, adipocytes, hepatocytes, and cells of the lung and the placenta. Binds directly to the consensus DNA sequence 5'-T[TG]NNGNAA[TG]-3' acting as an activator on distinct target genes (PubMed:11242107). During early embryogenesis, plays essential and redundant functions with CEBPB. Essential for the transition from common myeloid progenitors (CMP) to granulocyte/monocyte progenitors (GMP). Critical for the proper development of the liver and the lung (By similarity). Necessary for terminal adipocyte differentiation, is required for postnatal maintenance of systemic energy homeostasis and lipid storage (By similarity). To regulate these different processes at the proper moment and tissue, interplays with other transcription factors and modulators. Down-regulates the expression of genes that maintain cells in an undifferentiated and proliferative state through E2F1 repression, which is critical for its ability to induce adipocyte and granulocyte terminal differentiation. Reciprocally E2F1 blocks adipocyte differentiation by binding to specific promoters and repressing CEBPA binding to its target gene promoters. Proliferation arrest also depends on a functional binding to SWI/SNF complex (PubMed:14660596). In liver, regulates gluconeogenesis and lipogenesis through different mechanisms. To regulate gluconeogenesis, functionally cooperates with FOXO1 binding to IRE-controlled promoters and regulating the expression of target genes such as PCK1 or G6PC1. To modulate lipogenesis, interacts and transcriptionally synergizes with SREBF1 in promoter activation of specific lipogenic target genes such as ACAS2. In adipose tissue, seems to act as FOXO1 coactivator accessing to ADIPOQ promoter through FOXO1 binding sites (By similarity).[UniProtKB:P05554][UniProtKB:P53566][1] [2] Can act as dominant-negative. Binds DNA and have transctivation activity, even if much less efficiently than isoform 2. Does not inhibit cell proliferation (PubMed:14660596).[UniProtKB:P05554][UniProtKB:P53566][3] Directly and specifically enhances ribosomal DNA transcription interacting with RNA polymerase I-specific cofactors and inducing histone acetylation.[4] TRIB1_HUMAN Interacts with MAPK kinases and regulates activation of MAP kinases. May not display kinase activity.[5] [6] Publication Abstract from PubMedThe Tribbles family of pseudokinases recruits substrates to the ubiquitin ligase COP1 to facilitate ubiquitylation. CCAAT/enhancer-binding protein (C/EBP) family transcription factors are crucial Tribbles substrates in adipocyte and myeloid cell development. We found that the TRIB1 pseudokinase was able to recruit various C/EBP family members and that the binding of C/EBPbeta was attenuated by phosphorylation. To explain the mechanism of C/EBP recruitment, we solved the crystal structure of TRIB1 in complex with C/EBPalpha, which revealed that TRIB1 underwent a substantial conformational change relative to its substrate-free structure and bound C/EBPalpha in a pseudosubstrate-like manner. Crystallographic analysis and molecular dynamics and subsequent biochemical assays showed that C/EBP binding triggered allosteric changes that link substrate recruitment to COP1 binding. These findings offer a view of pseudokinase regulation with striking parallels to bona fide kinase regulation-by means of the activation loop and alphaC helix-and raise the possibility of small molecules targeting either the activation "loop-in" or "loop-out" conformations of Tribbles pseudokinases. Substrate binding allosterically relieves autoinhibition of the pseudokinase TRIB1.,Jamieson SA, Ruan Z, Burgess AE, Curry JR, McMillan HD, Brewster JL, Dunbier AK, Axtman AD, Kannan N, Mace PD Sci Signal. 2018 Sep 25;11(549). pii: 11/549/eaau0597. doi:, 10.1126/scisignal.aau0597. PMID:30254053[7] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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