5vey

Structural highlights

Function

[H2B1J_HUMAN] Core component of nucleosome. Nucleosomes wrap and compact DNA into chromatin, limiting DNA accessibility to the cellular machineries which require DNA as a template. Histones thereby play a central role in transcription regulation, DNA repair, DNA replication and chromosomal stability. DNA accessibility is regulated via a complex set of post-translational modifications of histones, also called histone code, and nucleosome remodeling.^{[1] [2] [3]} Has broad antibacterial activity. May contribute to the formation of the functional antimicrobial barrier of the colonic epithelium, and to the bactericidal activity of amniotic fluid.^{[4] [5] [6]} [RN169_HUMAN] Probable E3 ubiquitin-protein ligase that acts as a negative regulator of double-strand breaks (DSBs) repair following DNA damage. Recruited to DSB repair sites by recognizing and binding ubiquitin catalyzed by RNF168 and competes with TP53BP1 and BRCA1 for association with RNF168-modified chromatin, thereby acting as a negative regulator of DSBs repair. E3 ubiquitin-protein ligase activity is not required for regulation of DSBs repair.^{[7] [8] [9]} [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.^{[10] [11]}

References

1. ↑ Kim HS, Cho JH, Park HW, Yoon H, Kim MS, Kim SC. Endotoxin-neutralizing antimicrobial proteins of the human placenta. J Immunol. 2002 Mar 1;168(5):2356-64. PMID:11859126
2. ↑ Tollin M, Bergman P, Svenberg T, Jornvall H, Gudmundsson GH, Agerberth B. Antimicrobial peptides in the first line defence of human colon mucosa. Peptides. 2003 Apr;24(4):523-30. PMID:12860195
3. ↑ Howell SJ, Wilk D, Yadav SP, Bevins CL. Antimicrobial polypeptides of the human colonic epithelium. Peptides. 2003 Nov;24(11):1763-70. PMID:15019208 doi:10.1016/j.peptides.2003.07.028
4. ↑ Kim HS, Cho JH, Park HW, Yoon H, Kim MS, Kim SC. Endotoxin-neutralizing antimicrobial proteins of the human placenta. J Immunol. 2002 Mar 1;168(5):2356-64. PMID:11859126
5. ↑ Tollin M, Bergman P, Svenberg T, Jornvall H, Gudmundsson GH, Agerberth B. Antimicrobial peptides in the first line defence of human colon mucosa. Peptides. 2003 Apr;24(4):523-30. PMID:12860195
6. ↑ Howell SJ, Wilk D, Yadav SP, Bevins CL. Antimicrobial polypeptides of the human colonic epithelium. Peptides. 2003 Nov;24(11):1763-70. PMID:15019208 doi:10.1016/j.peptides.2003.07.028
7. ↑ Poulsen M, Lukas C, Lukas J, Bekker-Jensen S, Mailand N. Human RNF169 is a negative regulator of the ubiquitin-dependent response to DNA double-strand breaks. J Cell Biol. 2012 Apr 16;197(2):189-99. doi: 10.1083/jcb.201109100. Epub 2012 Apr, 9. PMID:22492721 doi:http://dx.doi.org/10.1083/jcb.201109100
8. ↑ Chen J, Feng W, Jiang J, Deng Y, Huen MS. Ring finger protein RNF169 antagonizes the ubiquitin-dependent signaling cascade at sites of DNA damage. J Biol Chem. 2012 Aug 10;287(33):27715-22. doi: 10.1074/jbc.M112.373530. Epub, 2012 Jun 25. PMID:22733822 doi:http://dx.doi.org/10.1074/jbc.M112.373530
9. ↑ Panier S, Ichijima Y, Fradet-Turcotte A, Leung CC, Kaustov L, Arrowsmith CH, Durocher D. Tandem protein interaction modules organize the ubiquitin-dependent response to DNA double-strand breaks. Mol Cell. 2012 Aug 10;47(3):383-95. doi: 10.1016/j.molcel.2012.05.045. Epub 2012 , Jun 27. PMID:22742833 doi:10.1016/j.molcel.2012.05.045
10. ↑ 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
11. ↑ 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