DESI1 Human

What is DESI1 and what is its primary function in human cells?

DESI1 (Desumoylating isopeptidase 1) is a protease that specifically removes SUMO1, SUMO2, and SUMO3 from substrate proteins . It possesses isopeptidase activity but lacks SUMO-processing capabilities, distinguishing it from other SUMO proteases . DESI1 collaborates with UBQLN4 in exporting ubiquitinated proteins from the nucleus to the cytoplasm . The protein belongs to the DeSI family and forms a critical component in the dynamic regulation of SUMOylation, a post-translational modification process essential for various cellular functions .

What is the molecular structure of DESI1?

DESI1 forms a homodimer with a unique structure where the groove between the two subunits constitutes the active site . This active site harbors two absolutely conserved cysteine and histidine residues that form a catalytic dyad essential for its enzymatic function . Unlike other SUMO proteases such as the SENP family, DESI1 belongs to the putative deubiquitinating isopeptidase PPPDE superfamily and exhibits an extremely low endopeptidase activity toward precursor forms of SUMO-1 and SUMO-2 . The canonical human DESI1 protein consists of 168 amino acid residues with a molecular mass of approximately 18.3 kDa .

Where is DESI1 expressed in human tissues and cells?

DESI1 is widely expressed across numerous tissue types in humans . At the subcellular level, DESI1 exhibits dual localization, being present in both the nucleus and cytoplasm . This dual localization is consistent with its roles in nuclear processes such as chromosome segregation and its cytoplasmic functions in protein trafficking . The widespread expression pattern suggests that DESI1 performs fundamental cellular functions across different tissue types rather than having tissue-specific roles.

What are the known synonyms and orthologs of DESI1?

DESI1 is known by several synonyms in the scientific literature, including:

DESI1 gene orthologs have been documented in multiple species including mouse, rat, bovine, frog, chimpanzee, and chicken, indicating evolutionary conservation of this protein across vertebrates .

How does DESI1 participate in chromosome segregation during cell division?

DESI1 plays a critical role in ensuring faithful chromosome segregation during cell division. Research demonstrates that knockdown of DESI1 accelerates cell division progression, resulting in significant increases in abnormal chromosome segregation . This phenotype can be rescued by re-expression of wild-type DESI1, but not by catalytically inactive DESI1, indicating that the isopeptidase activity is essential for this function .

Mechanistically, DESI1 influences the spindle assembly checkpoint (SAC), a critical quality control mechanism during mitosis. When DESI1 is knocked down, cells show reduced mitotic arrest in response to nocodazole treatment, suggesting compromised SAC function . At the molecular level, DESI1 maintains proper Aurora B (a key SAC regulator) expression and localization at metaphase chromosomes. DESI1 achieves this by regulating the transcriptional activity of FoxM1, which controls the expression of multiple mitotic genes including Aurora B, cyclin B1, and CENP-F .

What is the relationship between DESI1 and cancer development or treatment?

DESI1 has significant implications for cancer biology and treatment response. Analysis of The Cancer Genome Atlas (TCGA) database reveals that both decreased and increased DESI1 expression levels correlate with poor prognosis in patients with certain cancer types . This bidirectional relationship suggests a complex role in tumorigenesis that likely depends on cellular context and cancer type.

From a therapeutic perspective, DESI1 influences cancer cell response to chemotherapy. Research shows that DESI1 knockdown reduces cancer cell sensitivity to vincristine, a microtubule-targeting chemotherapeutic agent, by inducing mitotic slippage . This finding has important clinical implications, as it suggests that DESI1 expression levels could potentially serve as a biomarker for predicting responsiveness to certain chemotherapeutic regimens, particularly those targeting mitotic processes.

How does DESI1 differ from other desumoylating enzymes like SENPs?

DESI1 represents a distinct class of desumoylases that differs significantly from the SENP (sentrin/SUMO-specific protease) family, which was the first identified class of deSUMOylases . Key differences include:

These differences underscore the complexity of SUMO regulation in cells and suggest that DESI1 may have evolved to target specific subsets of SUMOylated proteins or to function in specific cellular contexts .

What are the recommended antibodies and techniques for detecting DESI1 in human samples?

For robust detection of DESI1 in human samples, Western blotting represents the most validated application for available anti-DESI1 antibodies . When selecting antibodies, researchers should consider:

• Antibody specificity: Anti-DESI1 antibodies targeting the C-terminal region have shown good specificity in Western blotting applications .

• Cross-reactivity: Some antibodies have demonstrated cross-reactivity with orthologs from multiple species including human, mouse, rat, canine, guinea pig, horse, and pig, which can be advantageous for comparative studies .

• Conjugation options: Both unconjugated primary antibodies and tagged variants are available depending on experimental requirements .

For subcellular localization studies, immunofluorescence using validated antibodies combined with confocal microscopy is recommended, particularly when investigating DESI1's dual localization in both nuclear and cytoplasmic compartments .

For evaluating DESI1 expression levels in tissue samples, immunohistochemistry using paraffin-embedded sections can provide valuable insights into expression patterns across different cell types within tissues.

How can researchers experimentally assess DESI1's desumoylating activity?

To assess DESI1's desumoylating activity, researchers can employ several complementary approaches:

• In vitro desumoylation assays: Purified recombinant DESI1 can be incubated with SUMOylated substrate proteins, followed by SDS-PAGE and Western blot analysis to monitor SUMO removal . For quantitative analysis, fluorescently labeled SUMO substrates can be used.

• Cell-based desumoylation assays: Researchers can overexpress or knock down DESI1 in cultured cells, then analyze the SUMOylation status of known DESI1 substrates by immunoprecipitation followed by Western blotting for SUMO.

• Catalytic mutant controls: Including catalytically inactive DESI1 (with mutations in the critical cysteine or histidine residues of the catalytic dyad) serves as an essential negative control to confirm that observed effects depend on DESI1's enzymatic activity rather than scaffolding functions .

• Specificity assessment: Testing activity against different SUMO isoforms (SUMO1, SUMO2, SUMO3) and comparing activity toward isopeptide bonds versus linear SUMO precursors helps characterize the enzyme's specificity .

When interpreting results, researchers should consider that DESI1 has isopeptidase activity (cleaving SUMO from conjugated proteins) but exhibits extremely low activity toward SUMO precursors, unlike some SENP family members .

What genetic tools are available for manipulating DESI1 expression in research models?

Several genetic tools are available for manipulating DESI1 expression in research models:

• RNA interference: siRNA and shRNA approaches have been successfully used to knock down DESI1 expression in cell culture models . These approaches allow for transient or stable knockdown depending on experimental requirements.

• CRISPR-Cas9 genome editing: For complete knockout studies or for generating epitope-tagged endogenous DESI1, CRISPR-Cas9 technology provides a precise tool. Researchers can target the DESI1 gene for knockout or introduce specific mutations to create catalytically inactive variants.

• Overexpression systems: Vectors for expressing wild-type DESI1 or catalytically inactive mutants (particularly mutations in the catalytic cysteine) are valuable for rescue experiments and structure-function studies .

• Inducible expression systems: Tetracycline-inducible or other inducible systems allow for temporal control of DESI1 expression or knockdown, which is particularly useful for studying dynamic processes like cell division.

• Animal models: While not explicitly mentioned in the search results, conditional knockout mouse models could be developed to study DESI1 function in specific tissues or developmental stages.

When designing genetic manipulation experiments, researchers should include appropriate controls, such as comparing the effects of wild-type DESI1 versus catalytically inactive mutants, to distinguish between enzymatic and potential scaffolding functions .

How does DESI1 regulate the spindle assembly checkpoint (SAC) during mitosis?

DESI1 regulates the spindle assembly checkpoint (SAC) during mitosis through multiple interconnected mechanisms:

• FoxM1 transcriptional regulation: DESI1 influences the transcriptional activity of FoxM1, a key transcription factor that controls the expression of numerous genes essential for mitosis . When DESI1 is knocked down, transcription of FoxM1 target genes, including Aurora B, cyclin B1, and CENP-F, is reduced .

• Aurora B expression and localization: DESI1 maintains proper expression levels of Aurora B, a critical component of the chromosomal passenger complex and a key SAC regulator . Additionally, DESI1 ensures proper localization of Aurora B at metaphase chromosomes. Upon DESI1 knockdown, both Aurora B expression and its localization at metaphase chromosomes are reduced .

• Nocodazole response: Cells with DESI1 knockdown show reduced mitotic arrest in response to nocodazole (a microtubule-depolymerizing agent that normally triggers SAC activation), providing functional evidence of compromised SAC activity .

Importantly, these regulatory functions depend on DESI1's isopeptidase activity, as evidenced by rescue experiments where wild-type DESI1, but not catalytically inactive DESI1, can restore normal phenotypes in knockdown cells . This suggests that DESI1 likely regulates the SUMOylation status of key proteins involved in SAC signaling, either directly or indirectly through FoxM1 regulation.

What is the clinical significance of DESI1 expression in cancer prognosis and treatment response?

DESI1 expression has significant clinical implications for cancer prognosis and treatment response:

• Prognostic value: Analysis of The Cancer Genome Atlas (TCGA) database reveals that both decreased and increased DESI1 expression levels are associated with poor prognosis in patients with certain cancer types . This bidirectional relationship suggests context-dependent roles in different cancer types or stages.

• Chemotherapy response prediction: DESI1 expression levels may predict response to certain chemotherapeutic agents, particularly those targeting mitotic processes. Specifically, DESI1 knockdown reduces sensitivity to vincristine by inducing mitotic slippage . This finding suggests that tumors with low DESI1 expression might be less responsive to vincristine treatment.

• Mechanism of chemoresistance: By promoting mitotic slippage (premature exit from mitosis without completing proper chromosome segregation), reduced DESI1 expression allows cancer cells to escape mitotic catastrophe and subsequent cell death that would normally be induced by anti-mitotic drugs like vincristine .

These findings position DESI1 as a potential biomarker for treatment stratification in cancer therapy and suggest that strategies to modulate DESI1 activity might enhance response to existing chemotherapeutic regimens, particularly those targeting mitotic processes.

How do DESI1 expression levels affect chromosome segregation and genomic stability?

DESI1 expression levels critically influence chromosome segregation and genomic stability through several mechanisms:

• Mitotic progression regulation: DESI1 knockdown accelerates cell division progression, suggesting that normal DESI1 levels help maintain the appropriate timing of mitotic events . Proper timing is critical for ensuring complete and accurate chromosome segregation.

• Chromosome segregation fidelity: Knockdown of DESI1 leads to a significant increase in abnormal chromosome segregation events . These abnormalities can result in aneuploidy (abnormal chromosome numbers) in daughter cells, a hallmark of many cancers and a driver of genomic instability.

• SAC activity maintenance: Through its regulation of FoxM1 transcriptional activity and downstream mitotic regulators like Aurora B, DESI1 helps maintain robust SAC activity . The SAC prevents premature anaphase onset until all chromosomes are properly attached to the mitotic spindle, thereby preventing chromosome missegregation.

• Dependence on enzymatic activity: The ability of DESI1 to ensure faithful chromosome segregation depends on its isopeptidase activity, as demonstrated by rescue experiments where wild-type DESI1, but not catalytically inactive DESI1, can restore normal chromosome segregation in knockdown cells . This indicates that DESI1 likely regulates the SUMOylation status of key proteins involved in chromosome segregation.

These findings establish DESI1 as a novel regulator of genomic stability, with potential implications for understanding mechanisms of chromosomal instability in cancer and other diseases characterized by defective chromosome segregation.

What are the specific substrate proteins targeted by DESI1's desumoylating activity?

Future research should employ proteomics approaches such as SUMO remnant immunoprecipitation coupled with mass spectrometry, comparing SUMOylated proteins in wild-type versus DESI1-depleted cells. Validation studies should confirm direct desumoylation using in vitro assays with purified components. Additionally, investigating whether DESI1 shows preference for specific SUMO paralogues (SUMO1 vs. SUMO2/3) in cellular contexts would provide valuable insights into its substrate specificity and biological functions .

How is DESI1 activity regulated during the cell cycle and in response to cellular stress?

The regulation of DESI1 activity during the cell cycle and in response to various cellular stresses represents an important knowledge gap. Given DESI1's role in chromosome segregation and cell division, its activity likely requires precise temporal control .

Research should examine whether DESI1 undergoes post-translational modifications (phosphorylation, SUMOylation, etc.) during cell cycle progression or in response to stresses like DNA damage or hypoxia. Cell synchronization experiments coupled with activity assays and mass spectrometry could reveal such regulatory mechanisms. Additionally, investigating whether DESI1's subcellular localization changes during the cell cycle could provide insights into its regulation and function. Understanding these regulatory mechanisms could reveal how DESI1 dysfunction contributes to disease states and potentially identify points for therapeutic intervention.

Could DESI1 be a viable therapeutic target for cancer treatment, particularly in combination with existing chemotherapies?

• Would DESI1 inhibition or activation be beneficial? The bidirectional relationship between DESI1 expression and cancer prognosis suggests context-dependent effects .

• Is DESI1 druggable? Structure-based drug design efforts would need to target its catalytic site or protein-protein interactions.

• What are the potential off-target effects? As DESI1 is widely expressed across tissues, systemic inhibition might cause undesirable side effects .

• Which cancer types would benefit most? Stratification studies correlating DESI1 expression with treatment outcomes across cancer types would help identify appropriate indications.

Research using patient-derived xenografts with varying DESI1 expression levels, tested against different treatment regimens, could provide valuable insights into its potential as a therapeutic target or biomarker for treatment stratification.

How does DESI1 functionally compare with other members of the DeSI family?

Although the search results don't provide detailed information on other DeSI family members, we can infer that DESI1 belongs to a distinct family of desumoylating enzymes with unique structural and functional characteristics compared to the SENP family . A thorough comparative analysis would examine substrate specificity, tissue expression patterns, and cellular functions of different DeSI family members.

Future research should investigate whether different DeSI family members show functional redundancy or have evolved distinct specificities and cellular roles. Comparative biochemical studies examining substrate preferences, along with cell-based studies examining the effects of depleting individual family members, would provide valuable insights into their relative contributions to cellular SUMO homeostasis.