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Query: UNIPROT:P62988 (Ubiquitin)
 4,326 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Post-translational modifiers of the SUMO (Small Ubiquitin-related Modifier) family have emerged as key regulators of protein function and fate. While the past few years have seen an enormous increase in knowledge on SUMO enzymes, substrates, and consequences of modification, regulation of SUMO conjugation is far from being understood. This brief review will provide an overview on recent advances concerning (i) the interplay between sumoylation and other post-translational modifications at the level of individual targets and (ii) global regulation of SUMO conjugation and deconjugation.
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PMID:SUMO: regulating the regulator. 1680 18

Posttranslational protein modifications are effective devices that cells use to control the functions of proteins. Ubiquitin-like protein modifiers (Ubls) are posttranslationally attached to proteins by enzymatic reactions that are similar to ubiquitin conjugation. SUMO (small ubiquitin-related modifier) family proteins are the most intriguing Ubls. Sumoylation is the covalent attachment of SUMO to target proteins. Neddylation is the process that conjugates the ubiquitin-like polypeptide Nedd8 to the conserved lysines of cullins. Cullin family proteins organize ubiquitin ligase complexes to target numerous cellular proteins for polyubiquitinylation and subsequent proteasomal degradation. Despite the similarities in their structure and in enzymatic reactions Ubls and ubiquitin have distinct functions. In contrast with polyubiquitinylation that targets modified proteins to proteasome degradation, the biological consequences of sumoylation include the increase of protein stability. Sumoylation also helps in the protein transport from the cytoplasm to nucleus of cells, regulates transcriptional activities of proteins and mediates the binding of the protein to other proteins. Neddylation has importance for cell cycle control, signal transmission, cell differentiation and DNA repair. Recent studies linked sumoylation and neddylation of several proteins to important diseases (neurodegenerative diseases, acute promyelocytic leukemia, type I diabetes and other disorders). The regulation of these postranslational modifications may provide new targets for therapeutic intervention in several human diseases.
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PMID:[Ubiquitins, proteasomes, sumoylation and application today and in future for cancer and other diseases therapy II. Sumoylation and neddylation as posttranslational modifications of proteins and their ubiquitinylation and its significance]. 1687 67

Fusion and affinity tags are popular tools for the expression of mammalian proteins in bacteria. To facilitate the selection of expression approaches, a systematic comparison was performed. We cloned, sequenced, and expressed in Escherichia coli ubiquitin- and SUMO-hDRS fusion proteins with biotin- or 6xHis-tags. The tagging of hDRS with ubiquitin or SUMO was necessary to express properly folded and biologically active enzyme. Similar enhancement of hDRS activity was obtained by fusion to ubiquitin or SUMO. Ubiquitin, SUMO, biotin, and hexahistidine tags did not appreciably interfere with hDRS activity. Fusion proteins were specifically cleaved without altering the N-terminal of hDRS. After cleavage hDRS remained soluble and active with a specific activity comparable to that of the fused protein. Similar activity was observed with biotin- and 6xHis-tagging of hDRS. Higher purity but significantly lower yields of hDRS were obtained using biotin-tagging. Overall we demonstrated ubiquitin and SUMO fusion proteins similarly enhanced the proper folding of hDRS expressed in E. coli. In comparison to previous expressions of hDRS as a GST fusion, ubiquitin, and SUMO fusions provided higher yields and easier purification and cleavage.
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PMID:Systematic analysis of fusion and affinity tags using human aspartyl-tRNA synthetase expressed in E. coli. 1743 17

Post-translational modification by ubiquitin and ubiquitin-like (UBL) proteins is a key mechanism for cellular control. The specificity of the enzymes of ubiquitination and their close paralogs is dependent on their molecular electrostatic potentials. For example, analysis of molecular electrostatic potentials and electrostatically key residues can account for the selectivity of different E1s (activating enzymes) and of different SUMO proteases. The molecular interactions of the ubiquitin conjugating enzymes, the ubiquitin family proteins (UFP) and UBL domains are discussed in detail. An interesting observation is that the Non Canonical Ubiquitin Conjugating Enzymes (NCUBEs) have electrostatic potentials that are more similar to the UBC9 orthologs, the SUMO conjugating enzymes, than they are to other ubiquitin conjugating enzymes. It had previously been suggested that UBC9 may select for SUMO based on its difference in electrostatic potential as compared to other E2s but the NCUBE exception suggests that this may not be the case. The web site http://www.ubiquitin-resource.org/ allows users to find the E2s most electrostatically similar to a query E2. Where possible, models have been made for all E2 domains in the SMART database (http://smart.embl-heidelberg.de/). A brief overview of molecular electrostatic potentials and their application to understanding protein function is also given.
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PMID:Structural and electrostatic properties of ubiquitination and related pathways. 1748 10

DNA repair is regulated on many levels by ubiquitination. In order to identify novel connections between DNA repair pathways and ubiquitin signaling, we used mass spectrometry to identify proteins that interact with lysine 6-linked polyubiquitin chains. From this proteomic screen, we identified the DNA repair protein WRNIP1 (Werner helicase-interacting protein 1), along with nucleosome assembly protein 1, as novel ubiquitin-interacting proteins. We found that a small zinc finger domain at the N terminus of WRNIP1 is sufficient and necessary for noncovalent ubiquitin binding. This ubiquitin-binding zinc finger (UBZ) domain binds polyubiquitin but not monoubiquitin and appears to show no specificity for polyubiquitin chain linkage. A homologous zinc finger domain in RAD18 also binds polyubiquitin, suggesting a wider role for the UBZ domain in DNA repair. The WRNIP1 ubiquitin-binding function, along with its previously established ATPase activity, suggests that WRNIP1 plays a role in the metabolism of ubiquitinated proteins. Supporting this model, deletion of MGS1, the yeast homolog of WRNIP1, slows the rate of ubiquitin turnover, rendering yeast resistant to cycloheximide. We also find that WRNIP1 is heavily modified with ubiquitin and SUMO, revealing complex layers in the involvement of ubiquitin pathway proteins in the regulation of DNA repair. The novel ubiquitin-binding ability of WRNIP1 sheds light on the role of UBZ domain-containing proteins in postreplication DNA repair.
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PMID:Werner helicase-interacting protein 1 binds polyubiquitin via its zinc finger domain. 1755 Aug 99

Ubiquitin-like modifications, which are carried out by similar biochemical mechanisms, regulate nearly every aspect of cellular function. Despite the recent advancements in characterizing their enzymology, our knowledge about the dynamic processes of these modifications is still fragmentary. In this study, we have uncovered an intrinsic affinity between the SUMO E2 and the Cys domain of SUMO E1. NMR studies in combination with paramagnetic spin labeling demonstrate that this interaction is mediated by previously unknown interfaces on both E1 and E2 and places the two catalytic Cys residues of the two enzymes in close proximity. Site-directed mutagenesis and enzymatic assays indicate that the interaction is fundamentally important for the transfer of SUMO from E1 to E2. Results from this study suggest that the interaction between E2 and the Cys domain of E1 participates in guiding the E2's translocation to E1's enzymatic active site in ubiquitin-like modifications.
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PMID:The intrinsic affinity between E2 and the Cys domain of E1 in ubiquitin-like modifications. 1764 65

We identify the SUMO-Targeted Ubiquitin Ligase (STUbL) family of proteins and propose that STUbLs selectively ubiquitinate sumoylated proteins and proteins that contain SUMO-like domains (SLDs). STUbL recruitment to sumoylated/SLD proteins is mediated by tandem SUMO interaction motifs (SIMs) within the STUbLs N-terminus. STUbL-mediated ubiquitination maintains sumoylation pathway homeostasis by promoting target protein desumoylation and/or degradation. Thus, STUbLs establish a novel mode of communication between the sumoylation and ubiquitination pathways. STUbLs are evolutionarily conserved and include: Schizosaccharomyces pombe Slx8-Rfp (founding member), Homo sapiens RNF4, Dictyostelium discoideum MIP1 and Saccharomyces cerevisiae Slx5-Slx8. Cells lacking Slx8-Rfp accumulate sumoylated proteins, display genomic instability, and are hypersensitive to genotoxic stress. These phenotypes are suppressed by deletion of the major SUMO ligase Pli1, demonstrating the specificity of STUbLs as regulators of sumoylated proteins. Notably, human RNF4 expression restores SUMO pathway homeostasis in fission yeast lacking Slx8-Rfp, underscoring the evolutionary functional conservation of STUbLs. The DNA repair factor Rad60 and its human homolog NIP45, which contain SLDs, are candidate STUbL targets. Consistently, Rad60 and Slx8-Rfp mutants have similar DNA repair defects.
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PMID:SUMO-targeted ubiquitin ligases in genome stability. 1776 65

The length and precise linkage of polyubiquitin chains is important for their biological activity. Although other ubiquitin-like proteins have the potential to form polymeric chains their identification in vivo is challenging and their functional role is unclear. Vertebrates express three small ubiquitin-like modifiers, SUMO-1, SUMO-2, and SUMO-3. Mature SUMO-2 and SUMO-3 are nearly identical and contain an internal consensus site for sumoylation that is missing in SUMO-1. Combining state-of-the-art mass spectrometry with an "in vitro to in vivo" strategy for post-translational modifications, we provide direct evidence that SUMO-1, SUMO-2, and SUMO-3 form mixed chains in cells via the internal consensus sites for sumoylation in SUMO-2 and SUMO-3. In vitro, the chain length of SUMO polymers could be influenced by changing the relative amounts of SUMO-1 and SUMO-2. The developed methodology is generic and can be adapted for the identification of other sumoylation sites in complex samples.
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PMID:In vivo identification of human small ubiquitin-like modifier polymerization sites by high accuracy mass spectrometry and an in vitro to in vivo strategy. 1793 7

LORIEN (encoding a protein that contains a SP-RING/Miz zinc-finger motif present in a group of proteins involved in the Small Ubiquitin-related Modifier -SUMO- conjugation pathway) and MAT2 (encoding the methionine adenosyltransferase -MAT-) genes are arranged as two alternating copies in a head-to-tail configuration, with the LORIEN gene as the first copy of the cluster. The 5880bp preceding the first LORIEN gene copy were compared to the same region of L. major, showing a 93% identity between them. Bioinformatic analysis of this region predicted the presence of a 747-bp ORF encoding a hypothetical protein of 248 amino acids. Transcription of this ORF was confirmed by run-on assays and RT-PCR. Expression of the LORIEN gene was tested in both the promastigote and amastigote stages. Transcription arrest evidenced that LORIEN mRNA stability was very similar in both stages of the parasite life cycle. Protein synthesis inhibition by cycloheximide led to an increase in the steady-state levels of LORIEN transcripts only during the promastigote stage, pointing out to the existence of different stage-dependent mechanisms operating on the post-transcriptional regulation of this gene. The role of the LORIEN untranslated regions (5'UTR and 3'UTR) in post-transcriptional regulation was analysed using the luciferase (luc) reporter gene. Results evidenced that the 5'UTR was responsible for a low reporter gene expression, whereas the intergenic region (IR) between LORIEN and MAT2 genes provided high luc levels. However, the 3'UTR seemed to lack regulatory elements. Basing on these results, a model of regulation for the LORIEN gene is proposed.
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PMID:Characterization of the 5' region of the Leishmania infantum LORIEN/MAT2 gene cluster and role of LORIEN flanking regions in post-transcriptional regulation. 1842 39

In this issue of Molecular Cell, Meulmeester et al. (2008) identify USP25 as a SUMO2/3-interacting protein and substrate. A USP25 SUMO interaction motif directs SUMO2/3 specificity, and SUMO modification diminishes USP25's ability to bind and degrade polyubiquitin chains.
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PMID:SUMO takes control of a ubiquitin-specific protease. 1853 59


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