• Title, Summary, Keyword: Ubiquitination

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PIG3 Regulates p53 Stability by Suppressing Its MDM2-Mediated Ubiquitination

  • Jin, Min;Park, Seon-Joo;Kim, Seok Won;Kim, Hye Rim;Hyun, Jin Won;Lee, Jung-Hee
    • Biomolecules & Therapeutics
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    • v.25 no.4
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    • pp.396-403
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    • 2017
  • Under normal, non-stressed conditions, intracellular p53 is continually ubiquitinated by MDM2 and targeted for degradation. However, in response to severe genotoxic stress, p53 protein levels are markedly increased and apoptotic cell death is triggered. Inhibiting the ubiquitination of p53 under conditions where DNA damage has occurred is therefore crucial for preventing the development of cancer, because if cells with severely damaged genomes are not removed from the population, uncontrolled growth can result. However, questions remain about the cellular mechanisms underlying the regulation of p53 stability. In this study, we show that p53-inducible gene 3 (PIG3), which is a transcriptional target of p53, regulates p53 stability. Overexpression of PIG3 stabilized both endogenous and transfected wild-type p53, whereas a knockdown of PIG3 lead to a reduction in both endogenous and UV-induced p53 levels in p53-proficient human cancer cells. Using both in vivo and in vitro ubiquitination assays, we found that PIG3 suppressed both ubiquitination- and MDM2-dependent proteasomal degradation of p53. Notably, we demonstrate that PIG3 interacts directly with MDM2 and promoted MDM2 ubiquitination. Moreover, elimination of endogenous PIG3 in p53-proficient HCT116 cells decreased p53 phosphorylation in response to UV irradiation. These results suggest an important role for PIG3 in regulating intracellular p53 levels through the inhibition of p53 ubiquitination.

The Macrophage-Specific Transcription Factor Can Be Modified Posttranslationally by Ubiquitination in the Lipopolysaccharide-Treated Macrophages

  • Jung, Jae-Woo;Choi, Jae-Chol;Kim, Jae-Yeol;Park, In-Won;Choi, Byoung-Whui;Shin, Jong-Wook;Christman, John William
    • Tuberculosis and Respiratory Diseases
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    • v.70 no.2
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    • pp.113-124
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    • 2011
  • Background: Macrophages are one of the most important inflammatory cells in innate immunity. PU.1 is a macrophage-specific transcription factor. Ubiquitins are the ultimate regulator of eukaryotic transcription. The ubiquitination process for PU.1 is unknown. This study investigated the lipopolysaccharide (LPS)-induced activation of PU.1 and its relation to ubiquitins in the macrophages. Methods: Raw264.7 cells, the primary cultured alveolar, pulmonary, and bone marrow derived macrophages were used. The Raw264.7 cells were treated with MG-132, $NH_4Cl$, lactacytin and LPS. Nitric oxide and prostaglandin D2 and E2 were measured. Immunoprecipitation and Western blots were used to check ubiquitination of PU.1. Results: The PU.1 ubiquitination increased after LPS ($1{\mu}g$/mL) treatment for 4 hours on Raw264.7 cells. The ubiquitination of PU.1 by LPS was increased by MG-132 or $NH_4Cl$ pretreatment. Two hours of LPS treatment on macrophages, PU.1 activation was not induced nor increased with the inhibition of proteasomes and/or lysosomes. The ubiquitination of PU.1 was increased in LPS-treated Raw264.7 cells at 12- and at 24 hours. LPS-treated cells increased nitric oxide production, which was diminished by MG-132 or $NH_4Cl$. LPS increased the production of $PGE_2$ in the alveolar and peritoneal macrophages of wild type mice; however, $PGE_2$ was blocked or diminished in Rac2 null mice. Pretreatment of lactacystin increased $PGE_2$, however it decreased the $PGD_2$ level in the macrophages derived from the bone marrow of B57/BL6 mice. Conclusion: LPS treatment in the macrophages ubiquitinates PU.1. Ubiquitination of PU.1 may be involved in synthesis of nitric oxide and prostaglandins.

Regulation of cellular functions of p53 by ubiquitination (유비퀴틴화에 의한 세포 내 p53의 기능 조절)

  • Jung, Jin-Hyuk;Lee, Joon-Young;Lee, Sun-Mi;Choe, Tae-Boo;An, Sung-Kwan
    • KSBB Journal
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    • v.24 no.3
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    • pp.217-226
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    • 2009
  • p53 undergoes various post-translational modifications, including phosphorylation, ubiquitination, sumoylation, acetylation, methylation, and poly(ADP-ribosyl)ation. Modification of p53 widely affects to various functions of p53. Acetylation and phosphorylation of p53 have been studied for regulating its transcriptional activity which is observed in various stress condition. Otherwise, ubiquitination of p53 by Mdm2 has been well-studied as a canonical ubiquitin-mediated proteasomal degradation pathway. Moreover several investigators have recently reported that ubiquitination of p53 modulates not only its proteasome-dependent degradation by poly-ubiquitination but also its localization and transcriptional activity by mono-ubiquitination which usually does not serve the proteasome dependent degradation. Here we review recent studies on the cellular functions of p53 regulated by post-translational modifications, particularly focusing on mechanisms of ubiquitination.

Direct characterization of E2-dependent target specificity and processivity using an artificial p27-linker-E2 ubiquitination system

  • Ryu, Kyoung-Seok;Choi, Yun-Seok;Ko, Jun-Sang;Kim, Seong-Ock;Kim, Hyun-Jung;Cheong, Hae-Kap;Jeon, Young-Ho;Choi, Byong-Seok;Cheong, Chae-Joon
    • BMB Reports
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    • v.41 no.12
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    • pp.852-857
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    • 2008
  • Little attention has been paid to the specificity between E2 and the target protein during ubiquitination, although RING-E3 induces a potential intra-molecular reaction by mediating the direct transfer of ubiquitin from E2 to the target protein. We have constructed artificial E2 fusion proteins in which a target protein (p27) is tethered to one of six E2s via a flexible linker. Interestingly, only three E2s (UbcH5b, hHR6b, and Cdc34) are able to ubiquitinate p27 via an intra-molecular reaction in this system. Although the first ubiquitination of p27 (p27-Ub) by Cdc34 is less efficient than that of UbcH5b and hHR6b, the additional ubiquitin attachment to p27-Ub by Cdc34 is highly efficient. The E2 core of Cdc34 provides specificity to p27, and the residues 184-196 are required for possessive ubiquitination by Cdc34. We demonstrate direct E2 specificity for p27 and also show that differential ubiquitin linkages can be dependent on E2 alone.

Synergistic effect of two E2 ubiquitin conjugating enzymes in SCFhFBH1 catalyzed polyubiquitination

  • Kim, Jeong-Hoon;Choi, Jin Sun;Kim, Sunhong;Kim, Kidae;Myung, Pyung Keun;Park, Sung Goo;Seo, Yeon-Soo;Park, Byoung Chul
    • BMB Reports
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    • v.48 no.1
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    • pp.25-29
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    • 2015
  • Ubiquitination is a post translational modification which mostly links with proteasome dependent protein degradation. This process has been known to play pivotal roles in the number of biological events including apoptosis, cell signaling, transcription and translation. Although the process of ubiquitination has been studied extensively, the mechanism of polyubiquitination by multi protein E3 ubiquitin ligase, SCF complex remains elusive. In the present study, we identified UbcH5a as a novel stimulating factor for poly-ubiquitination catalyzed by $SCF^{hFBH1}$ using biochemical fractionations and MALDI-TOF. Moreover, we showed that recombinant UbcH5a and Cdc34 synergistically stimulate $SCF^{hFBH1}$ catalyzed polyubiquitination in vitro. These data may provide an important cue to understand the mechanism how the SCF complex efficiently polyubiquitinates target substrates.

Effects of Paf1 complex components on H3K4 methylation in budding yeast (출아효모에서 Paf1 복합체의 구성원들이 H3의 네번째 라이신의 메틸화에 미치는 영향)

  • Oh, Jun-Soo;Lee, Jung-Shin
    • Korean Journal of Microbiology
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    • v.52 no.4
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    • pp.487-494
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    • 2016
  • In Saccharomyces cerevisiae, Paf1 complex consists of five proteins, and they are structurally and functionally well conserved in yeast, fruit fly, plants, and human. With binding to RNA polymerase II from transcription start site to termination site, Paf1 complex functions as a platform for recruiting many types of transcription factors to RNA polymerase II. Paf1 complex contributes to H2B ubiquitination and indirectly influences on H3K4 di- and tri-methylation by histone crosstalk. But the individual effects of five components in Paf1 complex on these two histone modifications including H2B ubiquitination and H3K4 methylation largely remained to be identified. In this study, we constructed the single-gene knockout mutants of each Paf1 complex component and observed H3K4 mono-, di-, and trimethylation as well as H2B ubiquitination in these mutants. Interestingly, in each ${\Delta}paf1$, ${\Delta}rtf1$, and ${\Delta}ctr9$ strain, we observed the dramatic defect in H3K4 monomethylation, which is independent of H2B ubiquitination, as well as H3K4 di- and trimethylation. However, the protein level of Set1, which is methyltransferase for H3K4, was not changed in these mutants. This suggests that Paf1 complex may directly influence on H3K4 methylation by directly regulating the activity of Set1 or the stability of Set1 complex in an H2B ubiquitination independent manner.

Regulation of Protein Degradation by Proteasomes in Cancer

  • Jang, Ho Hee
    • Journal of Cancer Prevention
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    • v.23 no.4
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    • pp.153-161
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    • 2018
  • Imbalance of protein homeostasis (proteostasis) is known to cause cellular malfunction, cell death, and diseases. Elaborate regulation of protein synthesis and degradation is one of the important processes in maintaining normal cellular functions. Protein degradation pathways in eukaryotes are largely divided into proteasome-mediated degradation and lysosome-mediated degradation. Proteasome is a multisubunit complex that selectively degrades 80% to 90% of cellular proteins. Proteasome-mediated degradation can be divided into 26S proteasome (20S proteasome + 19S regulatory particle) and free 20S proteasome degradation. In 1980, it was discovered that during ubiquitination process, wherein ubiquitin binds to a substrate protein in an ATP-dependent manner, ubiquitin acts as a degrading signal to degrade the substrate protein via proteasome. Conversely, 20S proteasome degrades the substrate protein without using ATP or ubiquitin because it recognizes the oxidized and structurally modified hydrophobic patch of the substrate protein. To date, most studies have focused on protein degradation via 26S proteasome. This review describes the 26S/20S proteasomal pathway of protein degradation and discusses the potential of proteasome as therapeutic targets for cancer treatment as well as against diseases caused by abnormalities in the proteolytic system.

Enigma of Small Peptides Ubiquitin and SUMO in Plants

  • Seo, Hak Soo
    • Korean Journal of Breeding Science
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    • v.42 no.4
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    • pp.339-343
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    • 2010
  • Post-translational covalent modifications by small molecules or peptides remodel target proteins. One such modification, made by ubiquitin or small ubiquitin-related modifier (SUMO), is a rapidly expanding field in cell signaling pathways. Ubiquitin attachment controls the turnover and degradation of target proteins while SUMO conjugation regulates their activity and function. Recent studies report many examples of cross-talk between ubiquitin and SUMO pathways, indicating that the boundary is no longer clear. Here, we review recent progress concerning how ubiquitin and SUMO participate in new regulatory roles in plant cell, and how ubiquitination and sumoylation control plant growth and development.