6h4h
Usp28 catalytic domain variant E593D in complex with UbPAUsp28 catalytic domain variant E593D in complex with UbPA
Structural highlights
Function[UBP28_HUMAN] Deubiquitinase involved in DNA damage response checkpoint and MYC proto-oncogene stability. Involved in DNA damage induced apoptosis by specifically deubiquitinating proteins of the DNA damage pathway such as CLSPN. Also involved in G2 DNA damage checkpoint, by deubiquitinating CLSPN, and preventing its degradation by the anaphase promoting complex/cyclosome (APC/C). In contrast, it does not deubiquitinate PLK1. Specifically deubiquitinates MYC in the nucleoplasm, leading to prevent MYC degradation by the proteasome: acts by specifically interacting with isoform 1 of FBXW7 (FBW7alpha) in the nucleoplasm and counteracting ubiquitination of MYC by the SCF(FBW7) complex. In contrast, it does not interact with isoform 4 of FBXW7 (FBW7gamma) in the nucleolus, allowing MYC degradation and explaining the selective MYC degradation in the nucleolus.[1] [2] [3] [4] [UBB_HUMAN] Ubiquitin exists either covalently attached to another protein, or free (unanchored). When covalently bound, it is conjugated to target proteins via an isopeptide bond either as a monomer (monoubiquitin), a polymer linked via different Lys residues of the ubiquitin (polyubiquitin chains) or a linear polymer linked via the initiator Met of the ubiquitin (linear polyubiquitin chains). Polyubiquitin chains, when attached to a target protein, have different functions depending on the Lys residue of the ubiquitin that is linked: Lys-6-linked may be involved in DNA repair; Lys-11-linked is involved in ERAD (endoplasmic reticulum-associated degradation) and in cell-cycle regulation; Lys-29-linked is involved in lysosomal degradation; Lys-33-linked is involved in kinase modification; Lys-48-linked is involved in protein degradation via the proteasome; Lys-63-linked is involved in endocytosis, DNA-damage responses as well as in signaling processes leading to activation of the transcription factor NF-kappa-B. Linear polymer chains formed via attachment by the initiator Met lead to cell signaling. Ubiquitin is usually conjugated to Lys residues of target proteins, however, in rare cases, conjugation to Cys or Ser residues has been observed. When polyubiquitin is free (unanchored-polyubiquitin), it also has distinct roles, such as in activation of protein kinases, and in signaling.[5] [6] Publication Abstract from PubMedDeubiquitinases have emerged as promising drug targets for cancer therapy. The two DUBs USP25 and USP28 share high similarity but vary in their cellular functions. USP28 is known for its tumor-promoting role, whereas USP25 is a regulator of the innate immune system and, recently, a role in tumorigenesis was proposed. We solved the structures of the catalytic domains of both proteins and established substantial differences in their activities. While USP28 is a constitutively active dimer, USP25 presents an auto-inhibited tetramer. Our data indicate that the activation of USP25 is not achieved through substrate or ubiquitin binding. USP25 cancer-associated mutations lead to activation in vitro and in vivo, thereby providing a functional link between auto-inhibition and the cancer-promoting role of the enzyme. Our work led to the identification of significant differences between USP25 and USP28 and provided the molecular basis for the development of new and highly specific anti-cancer drugs. Differential Oligomerization of the Deubiquitinases USP25 and USP28 Regulates Their Activities.,Sauer F, Klemm T, Kollampally RB, Tessmer I, Nair RK, Popov N, Kisker C Mol Cell. 2019 Mar 22. pii: S1097-2765(19)30140-6. doi:, 10.1016/j.molcel.2019.02.029. PMID:30926243[7] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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