The long-term goal of this study is to understand the function of protein modification by the ubiquitin like protein ISG15 in hematopoiesis. Hematopoiesis is a complex process of cell proliferation and differentiation. Regulation of hematopoiesis occurs at multiple levels including transcriptional regulation, signal transduction, and protein modification. We cloned a novel member of the deubiquitinating enzyme family, termed ubp43. Further studies have demonstrated that ubp43 is a protease that specifically removes the ubiquitin like protein ISG15 from protein conjugates. Like phosphorylation, ISG15ylation is a mechanism of protein modification. However, in contrast to phosphorylation only a limited understanding exists of the mechanisms and consequences of ISG15ylation. Type I interferon (IFNa/b) and LPS strongly upregulate both ubp43 expression and protein ISG15ylation. We have generated ubp43 knockout mice. Ubp43 deficient mice have shown fundamental defects in hematopoietic response to interferon and LPS treatment. Furthermore, ubp43 deficient cells have significantly enhanced type I interferon signaling and Statl is an ISG15ylated protein. This proposal tests the hypothesis that ubp43 is crucial for hematopoiesis under stress conditions, such as viral and bacterial infections, by regulating the ISG15ylation of important regulators of the JAK-STAT signaling pathway. The studies proposed in Specific Aim #1 will analyze the molecular mechanism of protein ISG15ylation using Statl as a model. The studies proposed in Specific Aim #2 will investigate the function of JAK-STAT signaling and Statl ISG15ylation in ubp43 function. The studies proposed in Specific Aim #3 will investigate the role of ubp43 in type I interferon signaling by identifying additional important JAK-STAT pathway regulators affected by protein ISG15ylation. The experiments proposed will address fundamental questions about protein ISG15ylation in hematopoiesis and interferon signaling.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Research Project (R01)
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Hematology Subcommittee 2 (HEM)
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Mufson, R Allan
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Scripps Research Institute
La Jolla
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Malakhova, Oxana A; Zhang, Dong-Er (2008) ISG15 inhibits Nedd4 ubiquitin E3 activity and enhances the innate antiviral response. J Biol Chem 283:8783-7
Rempel, Lea A; Austin, Kathleen J; Ritchie, Kenneth J et al. (2007) Ubp43 gene expression is required for normal Isg15 expression and fetal development. Reprod Biol Endocrinol 5:13
Zou, Weiguo; Kim, Jung-Hwan; Handidu, Adedayo et al. (2007) Microarray analysis reveals that Type I interferon strongly increases the expression of immune-response related genes in Ubp43 (Usp18) deficient macrophages. Biochem Biophys Res Commun 356:193-9
Kim, Keun Il; Yan, Ming; Malakhova, Oxana et al. (2006) Ube1L and protein ISGylation are not essential for alpha/beta interferon signaling. Mol Cell Biol 26:472-9
Dao, Chinh T; Luo, Jiann-Kae; Zhang, Dong-Er (2006) Retinoic acid-induced protein ISGylation is dependent on interferon signal transduction. Blood Cells Mol Dis 36:406-13
Malakhova, Oxana A; Kim, Keun Il; Luo, Jiann-Kae et al. (2006) UBP43 is a novel regulator of interferon signaling independent of its ISG15 isopeptidase activity. EMBO J 25:2358-67
Zou, Weiguo; Zhang, Dong-Er (2006) The interferon-inducible ubiquitin-protein isopeptide ligase (E3) EFP also functions as an ISG15 E3 ligase. J Biol Chem 281:3989-94
Dao, Chinh T; Zhang, Dong-Er (2005) ISG15: a ubiquitin-like enigma. Front Biosci 10:2701-22
Kim, Keun Il; Malakhova, Oxana A; Hoebe, Kasper et al. (2005) Enhanced antibacterial potential in UBP43-deficient mice against Salmonella typhimurium infection by up-regulating type I IFN signaling. J Immunol 175:847-54
Zou, Weiguo; Papov, Vladimir; Malakhova, Oxana et al. (2005) ISG15 modification of ubiquitin E2 Ubc13 disrupts its ability to form thioester bond with ubiquitin. Biochem Biophys Res Commun 336:61-8

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