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gene_info: Name=Dsup {ECO:0000303|PubMed:27649274}; ORFNames=RvY_17224 {ECO:0000303|PubMed:27649274};
organism_full: Ramazzottius varieornatus (Water bear) (Tardigrade).
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Question

Gene Research for Functional Annotation

⚠️ CRITICAL: Gene/Protein Identification Context

BEFORE YOU BEGIN RESEARCH: You MUST verify you are researching the CORRECT gene/protein. Gene symbols can be ambiguous, especially for less well-characterized genes from non-model organisms.

Target Gene/Protein Identity (from UniProt):

• UniProt Accession: P0DOW4
• Protein Description: RecName: Full=Damage suppressor protein {ECO:0000303|PubMed:27649274};
• Gene Information: Name=Dsup {ECO:0000303|PubMed:27649274}; ORFNames=RvY_17224 {ECO:0000303|PubMed:27649274};
• Organism (full): Ramazzottius varieornatus (Water bear) (Tardigrade).
• Protein Family: Not specified in UniProt
• Key Domains: Not specified in UniProt

MANDATORY VERIFICATION STEPS:

1. Check if the gene symbol "Dsup" matches the protein description above
2. Verify the organism is correct: Ramazzottius varieornatus (Water bear) (Tardigrade).
3. Check if protein family/domains align with what you find in literature
4. If you find literature for a DIFFERENT gene with the same or similar symbol, STOP

If Gene Symbol is Ambiguous or You Cannot Find Relevant Literature:

DO NOT PROCEED WITH RESEARCH ON A DIFFERENT GENE. Instead:
- State clearly: "The gene symbol 'Dsup' is ambiguous or literature is limited for this specific protein"
- Explain what you found (e.g., "Found extensive literature on a different gene with the same symbol in a different organism")
- Describe the protein based ONLY on the UniProt information provided above
- Suggest that the protein function can be inferred from domain/family information

Research Target:

Please provide a comprehensive research report on the gene Dsup (gene ID: Dsup, UniProt: P0DOW4) in RAMVA.

The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.

You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.

We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.

We are interested in where in or outside the cell the gene product carries out its function.

We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.

Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.

Output

Question: You are an expert researcher providing comprehensive, well-cited information.

Provide detailed information focusing on:
1. Key concepts and definitions with current understanding
2. Recent developments and latest research (prioritize 2023-2024 sources)
3. Current applications and real-world implementations
4. Expert opinions and analysis from authoritative sources
5. Relevant statistics and data from recent studies

Format as a comprehensive research report with proper citations. Include URLs and publication dates where available.
Always prioritize recent, authoritative sources and provide specific citations for all major claims.

Gene Research for Functional Annotation

⚠️ CRITICAL: Gene/Protein Identification Context

BEFORE YOU BEGIN RESEARCH: You MUST verify you are researching the CORRECT gene/protein. Gene symbols can be ambiguous, especially for less well-characterized genes from non-model organisms.

Target Gene/Protein Identity (from UniProt):

• UniProt Accession: P0DOW4
• Protein Description: RecName: Full=Damage suppressor protein {ECO:0000303|PubMed:27649274};
• Gene Information: Name=Dsup {ECO:0000303|PubMed:27649274}; ORFNames=RvY_17224 {ECO:0000303|PubMed:27649274};
• Organism (full): Ramazzottius varieornatus (Water bear) (Tardigrade).
• Protein Family: Not specified in UniProt
• Key Domains: Not specified in UniProt

MANDATORY VERIFICATION STEPS:

1. Check if the gene symbol "Dsup" matches the protein description above
2. Verify the organism is correct: Ramazzottius varieornatus (Water bear) (Tardigrade).
3. Check if protein family/domains align with what you find in literature
4. If you find literature for a DIFFERENT gene with the same or similar symbol, STOP

If Gene Symbol is Ambiguous or You Cannot Find Relevant Literature:

DO NOT PROCEED WITH RESEARCH ON A DIFFERENT GENE. Instead:
- State clearly: "The gene symbol 'Dsup' is ambiguous or literature is limited for this specific protein"
- Explain what you found (e.g., "Found extensive literature on a different gene with the same symbol in a different organism")
- Describe the protein based ONLY on the UniProt information provided above
- Suggest that the protein function can be inferred from domain/family information

Research Target:

Please provide a comprehensive research report on the gene Dsup (gene ID: Dsup, UniProt: P0DOW4) in RAMVA.

The research report should be a detailed narrative explaining the function, biological processes, and localization of the gene product. Citations should be given for all claims.

You should prioritize authoritative reviews and primary scientific literature when conducting research. You can supplement
this with annotations you find in gene/protein databases, but these can be outdated or inaccurate.

We are specifically interested in the primary function of the gene - for enzymes, what reaction is catalyzed, and what is the substrate specificity? For transporters, what is the substrate? For structural proteins or adapters, what is the broader structural role? For signaling molecules, what is the role in the pathway.

We are interested in where in or outside the cell the gene product carries out its function.

We are also interested in the signaling or biochemical pathways in which the gene functions. We are less interested in broad pleiotropic effects, except where these elucidate the precise role.

Include evidence where possible. We are interested in both experimental evidence as well as inference from structure, evolution, or bioinformatic analysis. Precise studies should be prioritized over high-throughput, where available.

Research Report: Functional Annotation of Damage suppressor protein (Dsup) from Ramazzottius varieornatus (UniProt P0DOW4)

Executive summary

The Ramazzottius varieornatus protein Dsup (damage suppressor; UniProt P0DOW4) is a tardigrade-unique, nuclear, chromatin-associated protein that increases cellular resistance to DNA damage caused by hydroxyl radicals generated during ionizing radiation and oxidative stress. The best-supported primary mechanism is direct nucleosome binding and physical shielding of chromatin DNA, mediated largely by a C-terminal HMGN-like nucleosome-binding motif and surrounding disordered regions. In heterologous systems, Dsup reduces DNA fragmentation and DNA damage markers (e.g., comet assay tail DNA; γ-H2AX foci) and improves post-irradiation cell viability/proliferation; however, effects are context dependent, including deleterious outcomes in neurons and broad transcriptional repression in Drosophila. (hashimoto2016extremotoleranttardigradegenome pages 7-8, chavez2019thetardigradedamage pages 12-13, escarcega2023thetardigradedamage pages 1-3, zarubin2023thetardigradedsup pages 1-2)

1) Verification of correct gene/protein identity (mandatory disambiguation)

• The target gene symbol Dsup in the retrieved literature refers to the tardigrade damage suppressor protein from Ramazzottius varieornatus, explicitly linked to UniProt P0DOW4 and described as a 445 aa (~42.8 kDa) protein discovered from the R. varieornatus genome. (zarubin2023thetardigradedsup pages 1-2, zarubin2024structuralstudyof pages 1-2, chavez2019thetardigradedamage pages 1-2)
• This matches the user-provided UniProt description (“Damage suppressor protein”; gene name Dsup; organism R. varieornatus). (zarubin2024structuralstudyof pages 1-2, chavez2019thetardigradedamage pages 1-2)

2) Key concepts and definitions (current understanding)

2.1 DNA damage endpoints commonly used in Dsup studies

• Comet assay: Single-cell gel electrophoresis used to quantify DNA fragmentation. “% DNA in comet tail” is used as a proxy for strand breaks; alkaline conditions capture primarily single-strand breaks/alkali-labile sites, while neutral conditions emphasize double-strand breaks. Dsup’s protective effect in human cells was assessed using both alkaline and neutral comet assays after X-ray or H2O2. (hashimoto2016extremotoleranttardigradegenome pages 7-8)
• γ-H2AX foci: phosphorylation of histone H2AX at DNA double-strand breaks (DSBs), quantified as nuclear foci. Dsup expression reduced γ-H2AX foci formation after X-ray irradiation in HEK293 cells. (hashimoto2016extremotoleranttardigradegenome pages 7-8)

2.2 Intrinsically disordered proteins (IDPs) and “fuzzy complexes”

• Dsup is now experimentally supported to be an intrinsically disordered protein; 2024 SAXS and CD studies report that Dsup remains largely disordered and forms a fuzzy complex with DNA (binding without folding into a single rigid structure). (zarubin2024structuralstudyof pages 1-2, zarubin2024structuralstudyof pages 7-8)

2.3 Nucleosome binding via an HMGN-like motif

• A conserved Dsup sequence region is similar to the nucleosome-binding domain core of vertebrate HMGN proteins (high mobility group N), and is functionally important for nucleosome binding and chromatin protection. (chavez2019thetardigradedamage pages 12-13)

3) Molecular identity, sequence/structural features, and localization

3.1 Protein features

• Dsup is described as 445 residues and ~42.8 kDa. (zarubin2023thetardigradedsup pages 1-2, chavez2019thetardigradedamage pages 1-2, zarubin2024structuralstudyof pages 1-2)
• Sequence/biophysical composition consistent with disorder: enriched in S/A/G/K/T residues (reported ~69.8% SAGKT), with a high fraction of charged residues; structural predictors and experiments support high disorder. (zarubin2024structuralstudyof pages 1-2, zarubin2024structuralstudyof pages 7-8)

3.2 Subcellular localization

• Dsup is characterized as a unique nuclear/chromatin-associated tardigrade protein; it was identified in chromatin-associated fractions and described as co-localized with nuclear DNA. (zarubin2023thetardigradedsup pages 1-2)
• Dsup is reported to show nuclear localization in mammalian cells, including primary cortical neurons (tagged constructs). (escarcega2023thetardigradedamage pages 1-3)

4) Primary biochemical function and mechanism

4.1 What Dsup “does” (functional annotation)

Dsup is not an enzyme and no catalytic reaction/substrate specificity is described in these sources. Instead, the primary function supported by direct experiments is:
- Chromatin/nucleosome binding with consequent physical protection of genomic DNA from hydroxyl radical-mediated cleavage. (chavez2019thetardigradedamage pages 1-2, chavez2019thetardigradedamage pages 12-13)

4.2 Binding target and specificity

• Dsup preferentially binds nucleosomes over free DNA and can bind nucleosomes simultaneously with histone H1, indicating it does not simply replace canonical chromatin components. (chavez2019thetardigradedamage pages 7-8, chavez2019thetardigradedamage pages 12-13)

4.3 Mechanistic determinants: C-terminus and HMGN-like motif

• Chavez et al. showed the C-terminal region (~aa 360–445) is essential for nucleosome binding. A deletion mutant (M1; removing 360–445) is nearly defective in nucleosome binding and chromatin protection, while a mutant altering the HMGN-like sequence (M2) is partially defective—supporting that nucleosome binding is required for hydroxyl-radical protection. (chavez2019thetardigradedamage pages 12-13)

4.4 Structural/biophysical mechanism (2024 update)

• Zarubin et al. (2024) experimentally demonstrated Dsup’s intrinsic disorder using SAXS and CD and reported an elongated, heterogeneous ensemble; they report ~62–66% disordered content and low α-helix content (~5–7%) and that DNA binding results in a fuzzy complex (no strong disorder-to-order transition). (zarubin2024structuralstudyof pages 7-8)

5) Quantitative effects and statistics from experimental studies

5.1 Human cells: reduced DNA fragmentation and damage signaling

Hashimoto et al. (2016; Nature Communications, published Sep 2016; URL: https://doi.org/10.1038/ncomms12808) demonstrated multiple protective phenotypes in HEK293 cells:
- Comet assays: Dsup suppressed DNA fragmentation caused by 10 Gy X-ray irradiation (alkaline comet assay), 100 μM H2O2 exposure, and reduced DSB-associated fragmentation after 5 Gy X-ray (neutral comet assay). The study reports large sample sizes (e.g., ≥203–300 comets per condition depending on assay). (hashimoto2016extremotoleranttardigradegenome pages 7-8)
- γ-H2AX foci: Dsup reduced γ-H2AX focus formation 1 h after 1 Gy X-ray, with ≥70 cells per condition for quantitative comparisons. (hashimoto2016extremotoleranttardigradegenome pages 7-8)
- Post-irradiation viability/proliferation: After 4 Gy X-ray, control cell counts stagnated or declined over days, whereas Dsup-expressing cells increased and retained proliferative capacity; Dsup knockdown abolished these improvements. (hashimoto2016extremotoleranttardigradegenome pages 8-10)

The key quantitative plots supporting these conclusions are shown in the extracted figure crops from the paper. (hashimoto2016extremotoleranttardigradegenome media 2c4506b0, hashimoto2016extremotoleranttardigradegenome media 1fc06bfd)

5.2 In vitro chromatin protection from hydroxyl radicals (biochemical system)

• Chavez et al. (2019; eLife, published Oct 2019; URL: https://doi.org/10.7554/eLife.47682) demonstrated that Dsup protects chromatin from hydroxyl radical-mediated cleavage in vitro, and that mutants defective in nucleosome binding lose protective activity, establishing a mechanistic link between binding and protection. (chavez2019thetardigradedamage pages 12-13)

6) Recent developments (prioritizing 2023–2024)

6.1 Proteomics and pathway-level changes after UV-C (2023)

Shaba et al. (2023; International Journal of Molecular Sciences, published Jun 2023; URL: https://doi.org/10.3390/ijms241411463) performed differential proteomics in Dsup-transfected (Dsup+) HEK293T cells under basal conditions and after UV-C exposure with recovery:
- Enrichment/network analyses implicated the unfolded protein response, mRNA processing/stability, cytoplasmic stress granules, DNA damage response, and telomere maintenance as Dsup-associated programs after stress. (shaba2023proteomicsrevealshow pages 8-12)
- A specific quantitative result reported is that relative telomere length was significantly longer in Dsup+ cells compared with Dsup− cells at 24 h recovery after UV-C (p < 0.01). (shaba2023proteomicsrevealshow pages 8-12)

Interpretation: these findings support a model where Dsup’s effects include not only direct DNA shielding but also remodeling of proteostasis and genome maintenance pathways in a mammalian context. (shaba2023proteomicsrevealshow pages 8-12)

6.2 Dsup can be detrimental in neurons (2023)

Escarcega et al. (2023; Molecular and Cellular Neuroscience, published Jun 2023; URL: https://doi.org/10.1016/j.mcn.2023.103826) reported a context-dependent effect:
- Dsup localized to the nucleus in primary cortical neurons and promoted chromatin condensation;
- Contrary to its protective role in transformed cell lines, Dsup expression in neurons was neurotoxic, associated with DNA double-strand breaks and neurodegeneration. (escarcega2023thetardigradedamage pages 1-3)

This is important for translational applications: Dsup is not uniformly protective across cell types, and chromatin binding may have adverse effects depending on transcriptional context and genome maintenance capacity. (escarcega2023thetardigradedamage pages 1-3)

6.3 Organism-level engineering and transcriptional side effects (2023)

Zarubin et al. (2023; iScience, published Jul 2023; URL: https://doi.org/10.1016/j.isci.2023.106998) engineered Dsup-expressing Drosophila melanogaster lines:
- Dsup expression increased survival after γ-ray irradiation and hydrogen peroxide exposure in flies. (zarubin2023thetardigradedsup pages 1-2)
- Transcriptome analyses revealed a large number of differentially expressed genes with >99% down-regulated, and the authors report Dsup can bind RNA, suggesting Dsup can act as a non-specific repressor of transcription (a major potential liability/pleiotropic effect). (zarubin2023thetardigradedsup pages 1-2)

6.4 Structural/biophysical confirmation of intrinsic disorder (2024)

Zarubin et al. (2024; Scientific Reports, published Oct 2024; URL: https://doi.org/10.1038/s41598-024-74335-2) provide updated mechanistic grounding:
- Dsup’s intrinsic disorder was experimentally verified using SAXS and CD, with quantitative estimates of disorder/secondary structure and ensemble heterogeneity;
- The study supports that Dsup forms a fuzzy complex with DNA and emphasizes electrostatic binding consistent with a shielding model. (zarubin2024structuralstudyof pages 7-8, zarubin2024structuralstudyof pages 1-2)

7) Current applications and real-world implementations

Across the cited literature, Dsup is primarily used as a genome-protective engineering factor in heterologous expression contexts:
- Human cultured cells: improved resistance to X-ray and oxidative DNA damage, as quantified by comet assays and DNA damage signaling markers, and improved proliferative recovery after irradiation—relevant to concepts in radioprotection and stress-tolerant cell manufacturing. (hashimoto2016extremotoleranttardigradegenome pages 7-8, hashimoto2016extremotoleranttardigradegenome pages 8-10)
- Model organisms (flies): enhanced resistance to irradiation/oxidative stress but with broad transcriptional repression and reduced locomotor activity, highlighting challenges for organism-level deployment. (zarubin2023thetardigradedsup pages 1-2)

8) Expert synthesis and analysis (authoritative interpretations)

• The biochemical evidence supports a direct model: Dsup binds nucleosomes and protects chromatin from hydroxyl radicals via coverage by disordered regions enriched in SAGK residues. (chavez2019thetardigradedamage pages 12-13)
• The combination of 2019 mechanistic mutant analysis and 2024 IDP/fuzzy-complex structural data is consistent with a “disordered chromatin shield” mechanism, dominated by electrostatic, multivalent contacts rather than sequence-specific recognition. (chavez2019thetardigradedamage pages 12-13, zarubin2024structuralstudyof pages 7-8)
• At the same time, 2023 systems-level studies highlight that Dsup can rewire proteostasis/telomere programs (human cells) and act as a transcriptional perturbant (flies), which may contribute to both beneficial phenotypes (stress survival) and harmful outcomes (neuronal toxicity). (shaba2023proteomicsrevealshow pages 8-12, zarubin2023thetardigradedsup pages 1-2, escarcega2023thetardigradedamage pages 1-3)

9) Evidence map (compact summary table)

Table: This table summarizes the experimentally supported functional annotation of Ramazzottius varieornatus Dsup (UniProt P0DOW4), including identity, localization, molecular mechanism, pathway effects, quantitative protection data, and known limitations. It is useful as a compact evidence map linking core claims to specific context IDs from the reviewed literature.

10) Key primary sources (with dates and URLs)

• Hashimoto T. et al. 2016-09. Nature Communications: “Extremotolerant tardigrade genome and improved radiotolerance of human cultured cells by tardigrade-unique protein.” https://doi.org/10.1038/ncomms12808 (hashimoto2016extremotoleranttardigradegenome pages 7-8)
• Chavez C. et al. 2019-10-01. eLife: “The tardigrade damage suppressor protein binds to nucleosomes and protects DNA from hydroxyl radicals.” https://doi.org/10.7554/eLife.47682 (chavez2019thetardigradedamage pages 1-2)
• Shaba E. et al. 2023-06. International Journal of Molecular Sciences: “Proteomics reveals how the tardigrade damage suppressor protein teaches transfected human cells to survive UV-C stress.” https://doi.org/10.3390/ijms241411463 (shaba2023proteomicsrevealshow pages 8-12)
• Escarcega R.D. et al. 2023-06. Molecular and Cellular Neuroscience: “The Tardigrade damage suppressor protein Dsup promotes DNA damage in neurons.” https://doi.org/10.1016/j.mcn.2023.103826 (escarcega2023thetardigradedamage pages 1-3)
• Zarubin M. et al. 2023-07. iScience: “The tardigrade Dsup protein enhances radioresistance in Drosophila melanogaster and acts as an unspecific repressor of transcription.” https://doi.org/10.1016/j.isci.2023.106998 (zarubin2023thetardigradedsup pages 1-2)
• Zarubin M. et al. 2024-10. Scientific Reports: “Structural study of the intrinsically disordered tardigrade damage suppressor protein (Dsup) and its complex with DNA.” https://doi.org/10.1038/s41598-024-74335-2 (zarubin2024structuralstudyof pages 7-8)

References

1. (hashimoto2016extremotoleranttardigradegenome pages 7-8): Takuma Hashimoto, Daiki D. Horikawa, Yuki Saito, Hirokazu Kuwahara, Hiroko Kozuka-Hata, Tadasu Shin-I, Yohei Minakuchi, Kazuko Ohishi, Ayuko Motoyama, Tomoyuki Aizu, Atsushi Enomoto, Koyuki Kondo, Sae Tanaka, Yuichiro Hara, Shigeyuki Koshikawa, Hiroshi Sagara, Toru Miura, Shin-ichi Yokobori, Kiyoshi Miyagawa, Yutaka Suzuki, Takeo Kubo, Masaaki Oyama, Yuji Kohara, Asao Fujiyama, Kazuharu Arakawa, Toshiaki Katayama, Atsushi Toyoda, and Takekazu Kunieda. Extremotolerant tardigrade genome and improved radiotolerance of human cultured cells by tardigrade-unique protein. Nature Communications, Sep 2016. URL: https://doi.org/10.1038/ncomms12808, doi:10.1038/ncomms12808. This article has 466 citations and is from a highest quality peer-reviewed journal.

2. (chavez2019thetardigradedamage pages 12-13): Carolina Chavez, Grisel Cruz-Becerra, Jia Fei, George A Kassavetis, and James T Kadonaga. The tardigrade damage suppressor protein binds to nucleosomes and protects dna from hydroxyl radicals. eLife, Oct 2019. URL: https://doi.org/10.7554/elife.47682, doi:10.7554/elife.47682. This article has 149 citations and is from a domain leading peer-reviewed journal.

3. (escarcega2023thetardigradedamage pages 1-3): Rocio Diaz Escarcega, Abhijeet A. Patil, Matthew D. Meyer, Jose F. Moruno-Manchon, Alexander D. Silvagnoli, Louise D. McCullough, and Andrey S. Tsvetkov. The tardigrade damage suppressor protein dsup promotes dna damage in neurons. Molecular and Cellular Neuroscience, 125:103826, Jun 2023. URL: https://doi.org/10.1016/j.mcn.2023.103826, doi:10.1016/j.mcn.2023.103826. This article has 24 citations and is from a peer-reviewed journal.

4. (zarubin2023thetardigradedsup pages 1-2): Mikhail Zarubin, Talyana Azorskaya, Olga Kuldoshina, Sergey Alekseev, Semen Mitrofanov, and Elena Kravchenko. The tardigrade dsup protein enhances radioresistance in drosophila melanogaster and acts as an unspecific repressor of transcription. iScience, 26:106998, Jul 2023. URL: https://doi.org/10.1016/j.isci.2023.106998, doi:10.1016/j.isci.2023.106998. This article has 32 citations and is from a peer-reviewed journal.

5. (zarubin2024structuralstudyof pages 1-2): Mikhail Zarubin, Tatiana Murugova, Yury Ryzhykau, Oleksandr Ivankov, Vladimir N. Uversky, and Elena Kravchenko. Structural study of the intrinsically disordered tardigrade damage suppressor protein (dsup) and its complex with dna. Scientific Reports, Oct 2024. URL: https://doi.org/10.1038/s41598-024-74335-2, doi:10.1038/s41598-024-74335-2. This article has 20 citations and is from a peer-reviewed journal.

6. (chavez2019thetardigradedamage pages 1-2): Carolina Chavez, Grisel Cruz-Becerra, Jia Fei, George A Kassavetis, and James T Kadonaga. The tardigrade damage suppressor protein binds to nucleosomes and protects dna from hydroxyl radicals. eLife, Oct 2019. URL: https://doi.org/10.7554/elife.47682, doi:10.7554/elife.47682. This article has 149 citations and is from a domain leading peer-reviewed journal.

7. (zarubin2024structuralstudyof pages 7-8): Mikhail Zarubin, Tatiana Murugova, Yury Ryzhykau, Oleksandr Ivankov, Vladimir N. Uversky, and Elena Kravchenko. Structural study of the intrinsically disordered tardigrade damage suppressor protein (dsup) and its complex with dna. Scientific Reports, Oct 2024. URL: https://doi.org/10.1038/s41598-024-74335-2, doi:10.1038/s41598-024-74335-2. This article has 20 citations and is from a peer-reviewed journal.

8. (chavez2019thetardigradedamage pages 7-8): Carolina Chavez, Grisel Cruz-Becerra, Jia Fei, George A Kassavetis, and James T Kadonaga. The tardigrade damage suppressor protein binds to nucleosomes and protects dna from hydroxyl radicals. eLife, Oct 2019. URL: https://doi.org/10.7554/elife.47682, doi:10.7554/elife.47682. This article has 149 citations and is from a domain leading peer-reviewed journal.

9. (hashimoto2016extremotoleranttardigradegenome pages 8-10): Takuma Hashimoto, Daiki D. Horikawa, Yuki Saito, Hirokazu Kuwahara, Hiroko Kozuka-Hata, Tadasu Shin-I, Yohei Minakuchi, Kazuko Ohishi, Ayuko Motoyama, Tomoyuki Aizu, Atsushi Enomoto, Koyuki Kondo, Sae Tanaka, Yuichiro Hara, Shigeyuki Koshikawa, Hiroshi Sagara, Toru Miura, Shin-ichi Yokobori, Kiyoshi Miyagawa, Yutaka Suzuki, Takeo Kubo, Masaaki Oyama, Yuji Kohara, Asao Fujiyama, Kazuharu Arakawa, Toshiaki Katayama, Atsushi Toyoda, and Takekazu Kunieda. Extremotolerant tardigrade genome and improved radiotolerance of human cultured cells by tardigrade-unique protein. Nature Communications, Sep 2016. URL: https://doi.org/10.1038/ncomms12808, doi:10.1038/ncomms12808. This article has 466 citations and is from a highest quality peer-reviewed journal.

10. (hashimoto2016extremotoleranttardigradegenome media 2c4506b0): Takuma Hashimoto, Daiki D. Horikawa, Yuki Saito, Hirokazu Kuwahara, Hiroko Kozuka-Hata, Tadasu Shin-I, Yohei Minakuchi, Kazuko Ohishi, Ayuko Motoyama, Tomoyuki Aizu, Atsushi Enomoto, Koyuki Kondo, Sae Tanaka, Yuichiro Hara, Shigeyuki Koshikawa, Hiroshi Sagara, Toru Miura, Shin-ichi Yokobori, Kiyoshi Miyagawa, Yutaka Suzuki, Takeo Kubo, Masaaki Oyama, Yuji Kohara, Asao Fujiyama, Kazuharu Arakawa, Toshiaki Katayama, Atsushi Toyoda, and Takekazu Kunieda. Extremotolerant tardigrade genome and improved radiotolerance of human cultured cells by tardigrade-unique protein. Nature Communications, Sep 2016. URL: https://doi.org/10.1038/ncomms12808, doi:10.1038/ncomms12808. This article has 466 citations and is from a highest quality peer-reviewed journal.

11. (hashimoto2016extremotoleranttardigradegenome media 1fc06bfd): Takuma Hashimoto, Daiki D. Horikawa, Yuki Saito, Hirokazu Kuwahara, Hiroko Kozuka-Hata, Tadasu Shin-I, Yohei Minakuchi, Kazuko Ohishi, Ayuko Motoyama, Tomoyuki Aizu, Atsushi Enomoto, Koyuki Kondo, Sae Tanaka, Yuichiro Hara, Shigeyuki Koshikawa, Hiroshi Sagara, Toru Miura, Shin-ichi Yokobori, Kiyoshi Miyagawa, Yutaka Suzuki, Takeo Kubo, Masaaki Oyama, Yuji Kohara, Asao Fujiyama, Kazuharu Arakawa, Toshiaki Katayama, Atsushi Toyoda, and Takekazu Kunieda. Extremotolerant tardigrade genome and improved radiotolerance of human cultured cells by tardigrade-unique protein. Nature Communications, Sep 2016. URL: https://doi.org/10.1038/ncomms12808, doi:10.1038/ncomms12808. This article has 466 citations and is from a highest quality peer-reviewed journal.

12. (shaba2023proteomicsrevealshow pages 8-12): Enxhi Shaba, Claudia Landi, Carlotta Marzocchi, Lorenza Vantaggiato, Luca Bini, Claudia Ricci, and Silvia Cantara. Proteomics reveals how the tardigrade damage suppressor protein teaches transfected human cells to survive uv-c stress. International Journal of Molecular Sciences, Jun 2023. URL: https://doi.org/10.3390/ijms241411463, doi:10.3390/ijms241411463. This article has 9 citations.

13. (cantara2025captaintardigradeand pages 7-8): Silvia Cantara, Tommaso Regoli, and Claudia Ricci. Captain tardigrade and its shield to protect dna. DNA, 5:27, Jun 2025. URL: https://doi.org/10.3390/dna5020027, doi:10.3390/dna5020027. This article has 3 citations.

14. (cantara2025captaintardigradeand pages 5-7): Silvia Cantara, Tommaso Regoli, and Claudia Ricci. Captain tardigrade and its shield to protect dna. DNA, 5:27, Jun 2025. URL: https://doi.org/10.3390/dna5020027, doi:10.3390/dna5020027. This article has 3 citations.

15. (cantara2025captaintardigradeand pages 2-4): Silvia Cantara, Tommaso Regoli, and Claudia Ricci. Captain tardigrade and its shield to protect dna. DNA, 5:27, Jun 2025. URL: https://doi.org/10.3390/dna5020027, doi:10.3390/dna5020027. This article has 3 citations.

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Citations

1. hashimoto2016extremotoleranttardigradegenome pages 7-8
2. chavez2019thetardigradedamage pages 12-13
3. zarubin2023thetardigradedsup pages 1-2
4. escarcega2023thetardigradedamage pages 1-3
5. zarubin2024structuralstudyof pages 7-8
6. hashimoto2016extremotoleranttardigradegenome pages 8-10
7. shaba2023proteomicsrevealshow pages 8-12
8. chavez2019thetardigradedamage pages 1-2
9. zarubin2024structuralstudyof pages 1-2
10. chavez2019thetardigradedamage pages 7-8
11. cantara2025captaintardigradeand pages 7-8
12. cantara2025captaintardigradeand pages 5-7
13. cantara2025captaintardigradeand pages 2-4
14. shaba2023proteomicsrevealshow pages 12-13
15. cantara2025captaintardigradeand pages 14-15
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Dsup (Damage Suppressor Protein) - Research Notes

Overview

Dsup (P0DOW4) is a tardigrade-unique protein from Ramazzottius varieornatus that protects DNA/chromatin from damage caused by reactive oxygen species (ROS) and ionizing radiation. It is an intrinsically disordered protein (IDP) of 445 amino acids with no known homologs outside tardigrades.

Key findings from literature

Discovery and initial characterization (PMID:27649274)

• Discovered through genome sequencing of R. varieornatus PMID:27649274
• Localizes to the nucleus and associates with DNA PMID:27649274
• Expression of Dsup in human HEK293T cells suppresses X-ray-induced DNA damage (both SSBs and DSBs) and improves radiotolerance PMID:27649274
• Also protects against ROS damage from hydrogen peroxide treatment PMID:27649274
• C-terminal region (aa 208-445) is required and sufficient for DNA binding and nuclear co-localization PMID:27649274

Nucleosome binding and hydroxyl radical protection (PMID:31571581)

• Dsup binds preferentially to nucleosomes over free DNA PMID:31571581
• Binds primarily to the nucleosome core rather than linker DNA PMID:31571581
• Can be incorporated into periodic nucleosome arrays without disrupting chromatin structure PMID:31571581
• Co-binds with histone H1 simultaneously to nucleosomes PMID:31571581
• Contains a conserved region with sequence similarity to HMGN nucleosome-binding domain PMID:31571581
• C-terminal region (aa 360-445) required for nucleosome binding and hydroxyl radical protection PMID:31571581
• Mutagenesis of RRSSR (363-367) to EESSE decreases nucleosome binding PMID:31571581
• Protects chromatin from hydroxyl radical-mediated cleavage in a purified biochemical system PMID:31571581
• Ortholog (Dsup-like) found in H. exemplaris with conserved nucleosome binding and DNA protection PMID:31571581

Structural characterization (PMID:39358423)

• Experimentally confirmed as an intrinsically disordered protein (IDP) by SAXS and CD spectroscopy PMID:39358423
• Forms fuzzy complex with DNA rather than rigid binding PMID:39358423
• Low-resolution models and ensemble of conformations generated PMID:39358423
• Protein is largely unstructured with hydrophilic properties and total positive charge PMID:39358423
• Also has RNA-binding ability [PMID:39358423, citing Kirke et al.]

Key GO terms to consider

• GO:0031491 nucleosome binding - strongly supported by PMID:31571581
• GO:0003677 DNA binding - already annotated (EXP)
• GO:0042262 DNA protection - core function
• GO:0005634 nucleus - already annotated (IEA)
• GO:0006974 DNA damage response - in UniProt as IEA keyword
• GO:0003682 chromatin binding - parent of nucleosome binding, supported

Notes

• Dsup is NOT an enzyme - it functions as a physical shield for DNA/chromatin
• The mechanism is direct: binding to nucleosomes physically protects DNA from hydroxyl radical damage
• This is NOT a DNA repair protein - it prevents damage rather than repairing it
• The protein is tardigrade-specific with only one known ortholog in H. exemplaris