6hek

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]}

References

1. ↑ Zhang D, Zaugg K, Mak TW, Elledge SJ. A role for the deubiquitinating enzyme USP28 in control of the DNA-damage response. Cell. 2006 Aug 11;126(3):529-42. PMID:16901786 doi:http://dx.doi.org/10.1016/j.cell.2006.06.039
2. ↑ Popov N, Wanzel M, Madiredjo M, Zhang D, Beijersbergen R, Bernards R, Moll R, Elledge SJ, Eilers M. The ubiquitin-specific protease USP28 is required for MYC stability. Nat Cell Biol. 2007 Jul;9(7):765-74. Epub 2007 Jun 10. PMID:17558397 doi:http://dx.doi.org/10.1038/ncb1601
3. ↑ Popov N, Herold S, Llamazares M, Schulein C, Eilers M. Fbw7 and Usp28 regulate myc protein stability in response to DNA damage. Cell Cycle. 2007 Oct 1;6(19):2327-31. Epub 2007 Jul 26. PMID:17873522
4. ↑ Bassermann F, Frescas D, Guardavaccaro D, Busino L, Peschiaroli A, Pagano M. The Cdc14B-Cdh1-Plk1 axis controls the G2 DNA-damage-response checkpoint. Cell. 2008 Jul 25;134(2):256-67. doi: 10.1016/j.cell.2008.05.043. PMID:18662541 doi:http://dx.doi.org/10.1016/j.cell.2008.05.043
5. ↑ Huang F, Kirkpatrick D, Jiang X, Gygi S, Sorkin A. Differential regulation of EGF receptor internalization and degradation by multiubiquitination within the kinase domain. Mol Cell. 2006 Mar 17;21(6):737-48. PMID:16543144 doi:S1097-2765(06)00120-1
6. ↑ Komander D. The emerging complexity of protein ubiquitination. Biochem Soc Trans. 2009 Oct;37(Pt 5):937-53. doi: 10.1042/BST0370937. PMID:19754430 doi:10.1042/BST0370937