Small ubiquitin-related modifier-1 (SUMO-1) modification of the glucocorticoid receptor.
Ontology highlight
ABSTRACT:
SUBMITTER: Tian S
PROVIDER: S-EPMC1222934 | biostudies-other | 2002 Nov
REPOSITORIES: biostudies-other
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Project description:Small ubiquitin-related modifiers (SUMOs) regulate diverse cellular processes through their covalent attachment to target proteins. Vertebrates express three SUMO paralogs: SUMO-1, SUMO-2, and SUMO-3 (SUMO-2 and SUMO-3 are approximately 96% identical and referred to as SUMO-2/3). SUMO-1 and SUMO-2/3 are conjugated, at least in part, to unique subsets of proteins and thus regulate distinct cellular pathways. However, how different proteins are selectively modified by SUMO-1 and SUMO-2/3 is unknown. We demonstrate that BLM, the RecQ DNA helicase mutated in Bloom syndrome, is preferentially modified by SUMO-2/3 both in vitro and in vivo. Our findings indicate that non-covalent interactions between SUMO and BLM are required for modification at non-consensus sites and that preferential SUMO-2/3 modification is determined by preferential SUMO-2/3 binding. We also present evidence that sumoylation of a C-terminal fragment of HIPK2 is dependent on SUMO binding, indicating that non-covalent interactions between SUMO and target proteins provide a general mechanism for SUMO substrate selection and possible paralog-selective modification.
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Project description:Modification by SUMO-1 is proposed to play a role in protein targeting and/or stability. The SUMO-1-conjugating enzyme Ubc9 interacts with androgen receptor (AR), a ligand-activated transcription factor belonging to the steroid receptor superfamily. We show here that AR is covalently modified by SUMO-1 (sumoylated) in an androgen-enhanced fashion and identify the principal acceptor site in the N-terminal domain of AR. Substitutions of sumoylated Lys residues enhanced transcriptional activity of AR without influencing its transrepressing activity. Interestingly, the same Lys residues form the cores of the recently described transcriptional synergy control motifs in AR [Iñiguez-Lluhi, J. A. & Pearce, D. (2000) Mol. Cell. Biol. 20, 6040-6050]. These motifs, which match perfectly with the sumoylation consensus sequence, are also present in the N-terminal domains of glucocorticoid, mineralocorticoid, and progesterone receptor. Taken together, our data suggest that reversible sumoylation is a mechanism for regulation of steroid receptor function.
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Project description:The neurodegenerative disorder spinal and bulbar muscular atrophy or Kennedy disease is caused by a CAG trinucleotide repeat expansion within the androgen receptor (AR) gene. The resulting expanded polyglutamine tract in the N-terminal region of the receptor renders AR prone to ligand-dependent misfolding and formation of oligomers and aggregates that are linked to neuronal toxicity. How AR misfolding is influenced by post-translational modifications, however, is poorly understood. AR is a target of SUMOylation, and this modification inhibits AR activity in a promoter context-dependent manner. SUMOylation is up-regulated in response to multiple forms of cellular stress and may therefore play an important cytoprotective role. Consistent with this view, we find that gratuitous enhancement of overall SUMOylation significantly reduced the formation of polyglutamine-expanded AR aggregates without affecting the levels of the receptor. Remarkably, this effect requires SUMOylation of AR itself because it depends on intact AR SUMOylation sites. Functional analyses, however, indicate that the protective effects of enhanced AR SUMOylation are not due to alterations in AR transcriptional activity because a branched protein structure in the appropriate context of the N-terminal region of AR is necessary to antagonize aggregation but not for inhibiting AR transactivation. Remarkably, small ubiquitin-like modifier (SUMO) attenuates AR aggregation through a unique mechanism that does not depend on critical features essential for its interaction with canonical SUMO binding motifs. Our findings therefore reveal a novel function of SUMOylation and suggest that approaches that enhance AR SUMOylation may be of clinical use in polyglutamine expansion diseases.
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Project description:Under conditions of hypoxia, most eukaryotic cells undergo a shift in metabolic strategy, which involves increased flux through the glycolytic pathway. Although this is critical for bioenergetic homeostasis, the underlying mechanisms have remained incompletely understood. Here, we report that the induction of hypoxia-induced glycolysis is retained in cells when gene transcription or protein synthesis are inhibited suggesting the involvement of additional post-translational mechanisms. Post-translational protein modification by the small ubiquitin related modifier-1 (SUMO-1) is induced in hypoxia and mass spectrometric analysis using yeast cells expressing tap-tagged Smt3 (the yeast homolog of mammalian SUMO) revealed hypoxia-dependent modification of a number of key glycolytic enzymes. Overexpression of SUMO-1 in mammalian cancer cells resulted in increased hypoxia-induced glycolysis and resistance to hypoxia-dependent ATP depletion. Supporting this, non-transformed cells also demonstrated increased glucose uptake upon SUMO-1 overexpression. Conversely, cells overexpressing the de-SUMOylating enzyme SENP-2 failed to demonstrate hypoxia-induced glycolysis. SUMO-1 overexpressing cells demonstrated focal clustering of glycolytic enzymes in response to hypoxia leading us to hypothesize a role for SUMOylation in promoting spatial re-organization of the glycolytic pathway. In summary, we hypothesize that SUMO modification of key metabolic enzymes plays an important role in shifting cellular metabolic strategies toward increased flux through the glycolytic pathway during periods of hypoxic stress.
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Project description:The small ubiquitin-related modifier (SUMO) system has been implicated in a number of biological functions, yet the individual components of the SUMO machinery involved in each of these activities were largely unknown. Here we report the first global SUMO system interactome. Using affinity purification coupled with mass spectrometry, we identify >450 protein-protein interactions surrounding the SUMO E2, Siz type E3s and SUMO-specific proteases in budding yeast. Exploiting this information-rich resource, we validate several Siz1- and Siz2-specific substrates, identify a nucleoporin required for proper Ulp1 localization, and uncover important new roles for Ubc9 and Ulp2 in the maintenance of ribosomal DNA.
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Project description:Thyroid hormone receptor (TR) ? and ? mediate thyroid hormone action at target tissues. TR isoforms have specific roles in development and in adult tissues. The mechanisms underlying TR isoform-specific action, however, are not well understood. We demonstrate that posttranslational modification of TR by conjugation of small SUMO to TR? and TR? plays an important role in triiodothyronine (T3) action and TR isoform specificity. TR? was sumoylated at lysines 283 and 389, and TR? at lysines 50, 146, and 443. Sumoylation of TR? was ligand-dependent, and sumoylation of TR? was ligand-independent. TR?-SUMO conjugation utilized the E3 ligase PIASx? and TR?-SUMO conjugation utilized predominantly PIAS1. SUMO1 and SUMO3 conjugation to TR was important for T3-dependent gene regulation, as demonstrated in transient transfection assay and studies of endogenous gene regulation. The functional role of SUMO1 and SUMO3 in T3 induction in transient expression assays was closely matched to the pattern of TR and cofactor recruitment to thyroid hormone response elements (TREs) as determined by ChIP assays. SUMO1 was required for the T3-induced recruitment of the co-activator CREB-binding protein (CBP) and release of nuclear receptor co-repressor (NCoR) on a TRE but had no significant effect on TR DNA binding. SUMO1 was required for T3-mediated recruitment of NCoR and release of CBP from the TSH?-negative TRE. SUMO3 was required for T3-stimulated TR binding to the TSH?-negative TRE and recruitment of NCoR. These findings demonstrate that conjugation of SUMO to TR has a TR-isoform preference and is important for T3-dependent gene induction and repression.
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Project description:Although it is well established that ubiquitin-like modifications are tightly regulated, it has been unclear how their E1 activities are controlled. In this study, we found that the SAE2 subunit of the small ubiquitin-like modifier (SUMO) E1 is autoSUMOylated at residue Lys-236, and SUMOylation was catalyzed by Ubc9 at several additional Lys residues surrounding the catalytic Cys-173 of SAE2. AutoSUMOylation of SAE2 did not affect SUMO adenylation or formation of E1·SUMO thioester, but did significantly inhibit the transfer of SUMO from E1 to E2 and overall SUMO conjugations to target proteins due to the altered interaction between E1 and E2. Upon heat shock, SUMOylation of SAE2 was reduced, which corresponded with an increase in global SUMOylation, suggesting that SUMOylation of the Cys domain of SAE2 is a mechanism for "storing" a pool of E1 that can be quickly activated in response to environmental changes. This study is the first to show how E1 activity is controlled by post-translational modifications, and similar regulation likely exists across the homologous E1s of ubiquitin-like modifications.
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Project description:Nonvisual arrestins are regulated by direct post-translational modifications, such as phosphorylation, ubiquitination, and nitrosylation. However, whether arrestins are regulated by other post-translational modifications remains unknown. Here we show that nonvisual arrestins are modified by small ubiquitin-like modifier 1 (SUMO-1) upon activation of ?(2)-adrenergic receptor (?(2)AR). Lysine residues 295 and 400 in arrestin-3 fall within canonical SUMO consensus sites, and mutagenic analysis reveals that Lys-400 represents the main SUMOylation site. Depletion of the SUMO E2 modifying enzyme Ubc9 blocks arrestin-3 SUMOylation and attenuates ?(2)AR internalization, suggesting that arrestin SUMOylation mediates G protein-coupled receptor endocytosis. Consistent with this, expression of a SUMO-deficient arrestin mutant failed to promote ?(2)AR internalization as compared with wild-type arrestin-3. Our data reveal an unprecedented role for SUMOylation in mediating GPCR endocytosis and provide novel mechanistic insight into arrestin function and regulation.
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Project description:The availability of the complete DNA sequence of the Chlamydomonas reinhardtii genome and advanced computational biology tools has allowed elucidation and study of the small ubiquitin-like modifier (SUMO) system in this unicellular photosynthetic alga and model eukaryotic cell system. SUMO is a member of a ubiquitin-like protein superfamily that is covalently attached to target proteins as a post-translational modification to alter the localization, stability, and/or function of the target protein in response to changes in the cellular environment. Three SUMO homologs (CrSUMO96, CrSUMO97, and CrSUMO148) and three novel SUMO-related proteins (CrSUMO-like89A, CrSUMO-like89B, and CrSUMO-like90) were found by diverse gene predictions, hidden Markov models, and database search tools inferring from Homo sapiens, Saccharomyces cerevisiae, and Arabidopsis thaliana SUMOs. Among them, CrSUMO96, which can be recognized by the A. thaliana anti-SUMO1 antibody, was studied in detail. Free CrSUMO96 was purified by immunoprecipitation and identified by mass spectrometry analysis. A SUMO-conjugating enzyme (SCE) (E2, Ubc9) in C. reinhardtii was shown to be functional in an Escherichia coli-based in vivo chimeric SUMOylation system. Antibodies to CrSUMO96 recognized free and conjugated forms of CrSUMO96 in Western blot analysis of whole-cell extracts and nuclear localized SUMOylated proteins with in situ immunofluorescence. Western blot analysis showed a marked increase in SUMO conjugated proteins when the cells were subjected to environmental stresses, such as heat shock and osmotic stress. Related analyses revealed multiple potential ubiquitin genes along with two Rub1 genes and one Ufm1 gene in the C. reinhardtii genome.
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Project description:SUMO proteases can regulate the amounts of SUMO-conjugated proteins in the cell by cleaving off the isopeptidic bond between SUMO and the target protein. Of the six members that constitute the human SENP/ULP protease family, SENP6 and SENP7 are the most divergent members in their conserved catalytic domain. The SENP6 and SENP7 subclass displays a clear proteolytic cleavage preference for SUMO2/3 isoforms. To investigate the structural determinants for such isoform specificity, we have identified a unique sequence insertion in the SENP6 and SENP7 subclass that is essential for their proteolytic activity and that forms a more extensive interface with SUMO during the proteolytic reaction. Furthermore, we have identified a region in the SUMO surface determinant for the SUMO2/3 isoform specificity of SENP6 and SENP7. Double point amino acid mutagenesis on the SUMO surface allows us to swap the specificity of SENP6 and SENP7 between the two SUMO isoforms. Structure-based comparisons combined with biochemical and mutagenesis analysis have revealed Loop 1 insertion in SENP6 and SENP7 as a platform to discriminate between SUMO1 and SUMO2/3 isoforms in this subclass of the SUMO protease family.
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