Affinage

DAD1

Dolichyl-diphosphooligosaccharide--protein glycosyltransferase subunit DAD1 · UniProt P61803

Length
113 aa
Mass
12.5 kDa
Annotated
2026-06-09
40 papers in source corpus 14 papers cited in narrative 12 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 6/6 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

DAD1 is an essential integral ER membrane protein that functions as a non-catalytic subunit of the oligosaccharyltransferase (OST) complex and is required for efficient N-linked glycosylation of nascent polypeptides (PMID:7593165, PMID:9144178, PMID:9167970). Identified through complementation cloning as the gene whose loss triggers apoptosis in temperature-sensitive tsBN7 hamster cells (PMID:8413235), it is the mammalian ortholog of the yeast OST ε-subunit Ost2p, which is essential for viability and OST activity (PMID:7593165). In purified mammalian OST, DAD1 is present in roughly equimolar amounts with OST48 and the ribophorins and can be chemically crosslinked into OST48-containing heteromers, defining it as a tightly associated structural subunit (PMID:9144178); topologically it spans the ER membrane with both termini in the cytosol (PMID:9167970). DAD1 is required for the structural integrity and enzymatic function of the complex: its loss destabilizes the entire OST (rendering OST48 nearly undetectable and reducing ribophorins) and disrupts assembly of both STT3A- and STT3B-containing complexes, producing global hypoglycosylation (PMID:9748289, PMID:22467853). Consequent failure to glycosylate substrates is the proximate cause of death—loss of DAD1 in vivo causes abnormal N-glycoproteins, increased tissue apoptosis, and embryonic lethality in mice (PMID:10720432, PMID:10748466, PMID:10336695), and in cardiomyocytes impairs N-glycosylation of integrins α5/β1, reduces focal adhesion kinase signaling, and induces anoikis that is rescued by restoring cell adhesion (PMID:39611549). Within intact ER membranes, functionally incorporated DAD1 diffuses very slowly, reflecting assembly into large ribosome-translocon polysome arrays from which it does not fully dissociate after translation terminates (PMID:12163472).

Mechanistic history

Synthesis pass · year-by-year structured walk · 11 steps
  1. 1993 High

    Established DAD1 as a gene whose loss causes apoptosis, framing a novel suppressor of cell death and identifying the causative point mutation in tsBN7 cells.

    Evidence DNA-mediated complementation cloning, cDNA sequencing, and Western blot in tsBN7 hamster cells

    PMID:8413235

    Open questions at the time
    • Molecular function of the protein not defined
    • Mechanism linking protein loss to apoptosis unknown
  2. 1995 High

    Assigned DAD1 a biochemical function by showing its yeast ortholog Ost2p is the essential ε-subunit of oligosaccharyltransferase, reframing the apoptosis phenotype as a glycosylation defect.

    Evidence Genomic disruption (lethality), conditional ost2 mutants, in vitro OST activity assays, and genetic suppression of wbp1-2 in S. cerevisiae

    PMID:7593165

    Open questions at the time
    • Direct demonstration of mammalian DAD1 in the OST complex not yet shown
    • Catalytic vs structural role unresolved
  3. 1995 High

    Demonstrated that DAD1 expression is sufficient to suppress programmed cell death and that function is conserved across species.

    Evidence Inducible overexpression of human and Ce-dad-1 in transgenic C. elegans with corpse counting and cross-species rescue of tsBN7 cells

    PMID:7556086

    Open questions at the time
    • Whether suppression reflects glycosylation function rather than a direct anti-apoptotic activity not distinguished
  4. 1997 High

    Confirmed mammalian DAD1 as a tightly associated, equimolar subunit of purified OST and mapped its membrane topology.

    Evidence Sedimentation velocity, radioiodination, chemical crosslinking in microsomes, and proteinase K protection topology mapping

    PMID:9144178 PMID:9167970

    Open questions at the time
    • Precise interaction interfaces within the complex not resolved
    • No high-resolution structure
  5. 1998 High

    Showed DAD1 is required for both structural integrity and enzymatic activity of the OST complex, not merely an accessory factor.

    Evidence Western blot of OST subunits and pulse-chase glycosylation in tsBN7 cells at permissive/non-permissive temperatures

    PMID:9748289

    Open questions at the time
    • Mechanism by which DAD1 stabilizes OST48/ribophorins not defined at molecular level
  6. 2000 Medium

    Tested whether DAD1 has a direct anti-apoptotic role via Bcl-2 family interaction, and dissociated OST function from Mcl-1 binding.

    Evidence Yeast two-hybrid, co-IP in COS cells, deletion mutagenesis, and tsBN7 complementation

    PMID:10965038

    Open questions at the time
    • Co-IP performed in overexpression system without reciprocal endogenous validation
    • Physiological significance of Mcl-1 interaction unestablished
  7. 2000 High

    Established the in vivo requirement of Dad1 for N-glycoprotein processing and cell survival during mammalian development.

    Evidence Targeted null mice analyzed by Western blot for N-glycoproteins, histology, and TUNEL

    PMID:10336695 PMID:10720432 PMID:10748466

    Open questions at the time
    • Tissue-specific apoptosis sensitivity not mechanistically explained
    • Specific glycoprotein substrates driving lethality not identified
  8. 2002 High

    Revealed the supramolecular context of DAD1, showing functional OST is tethered within slowly diffusing ribosome-translocon arrays.

    Evidence FRAP of functional GFP-Dad1 in live cells with protein synthesis inhibition

    PMID:12163472

    Open questions at the time
    • Molecular basis of OST retention in inactive translocons unknown
  9. 2006 Medium

    Tested whether the apoptosis-causing mutation reflects a direct pro-apoptotic function, concluding death is secondary to glycosylation loss.

    Evidence Site-directed Ost2 mutagenesis, viability and phosphatidylserine assays, and osmotic suppression with sorbitol in S. cerevisiae

    PMID:16717427

    Open questions at the time
    • Single-organism (yeast) inference about mammalian apoptosis mechanism
    • Lack of DNA fragmentation leaves death pathway incompletely defined
  10. 2012 High

    Generalized DAD1's structural role to both mammalian OST isoforms, defining it as required for STT3A- and STT3B-containing complex integrity.

    Evidence Subunit-specific siRNA knockdowns with OST assembly, activity, and glycosylation profiling

    PMID:22467853

    Open questions at the time
    • Whether DAD1 contributes differentially to co- vs post-translational glycosylation not resolved
  11. 2024 Medium

    Connected DAD1 loss to a specific physiological pathway, showing hypoglycosylation of integrins disrupts adhesion signaling and triggers anoikis.

    Evidence siRNA knockdown in neonatal rat cardiomyocytes with integrin glycosylation, FAK activation, morphology, adhesion-rescue, and Stt3A cross-knockdown assays

    PMID:39611549

    Open questions at the time
    • Single cell-type and single lab
    • Whether integrin hypoglycosylation is the dominant death trigger in other tissues unknown

Open questions

Synthesis pass · forward-looking unresolved questions
  • How DAD1 mechanistically stabilizes the OST complex and is retained in translocon arrays, and the full substrate spectrum whose hypoglycosylation drives apoptosis, remain unresolved.
  • No high-resolution structure of DAD1 within human OST in the corpus
  • Substrates linking hypoglycosylation to tissue-specific apoptosis incompletely defined

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0140098 catalytic activity, acting on RNA 4 GO:0005198 structural molecule activity 3
Localization
GO:0005783 endoplasmic reticulum 2
Pathway
R-HSA-392499 Metabolism of proteins 4 R-HSA-5357801 Programmed Cell Death 3
Partners
MCL1OST48RPN1RPN2STT3A
Complex memberships
oligosaccharyltransferase (OST) complex

Evidence

Reading pass · 12 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1993 DAD1 encodes a novel hydrophobic (integral membrane) protein whose loss triggers apoptosis; a point mutation in DAD1 is responsible for the temperature-sensitive apoptotic phenotype of tsBN7 hamster cells, and disappearance of the DAD1 protein at non-permissive temperature precedes cell death. DNA-mediated gene transfer complementation cloning; sequence comparison of parental and mutant cDNAs; Western blot showing protein disappearance Molecular and cellular biology High 8413235
1995 The yeast OST2 gene (DAD1 ortholog) encodes the ε-subunit of the oligosaccharyltransferase (OST); OST2 is essential for viability, and ost2 mutants show pleiotropic underglycosylation of soluble and membrane-bound glycoproteins and reduced in vitro OST activity. Overexpression of Ost2p suppresses the temperature-sensitive wbp1-2 allele and increases OST activity. Genomic disruption (lethal in haploid yeast); conditional ost2 mutant analysis; in vitro OST activity assay with lipid-linked oligosaccharide substrate; sequence analysis linking Ost2p to DAD1 The Journal of cell biology High 7593165
1995 C. elegans Ce-dad-1 and human dad-1, when overexpressed under a heat-shock promoter in C. elegans, reduce the number of programmed cell death corpses in embryos, demonstrating that DAD1 is sufficient to suppress developmentally programmed cell death. Ce-dad-1 also rescues tsBN7 hamster cells from apoptosis. Transgenic C. elegans expressing human or Ce-dad-1 under inducible promoter; cell death corpse counting; cross-species rescue of tsBN7 cells The EMBO journal High 7556086
1997 DAD1 is a tightly associated subunit of the mammalian oligosaccharyltransferase (OST) complex, present in roughly equimolar amounts with ribophorin I, ribophorin II, and OST48 in the purified enzyme. DAD1 cosediments with OST activity and can be crosslinked to OST48 in intact microsomes; higher-order crosslinked heterotrimers and heterotetramers (DAD1–ribophorin II–OST48; DAD1–ribophorin I–ribophorin II–OST48) are detected. Sedimentation velocity analysis; radioiodination of purified OST; chemical crosslinking (dithiobis(succinimidylpropionate)) in intact microsomes Proceedings of the National Academy of Sciences of the United States of America High 9144178
1997 DAD1 is an integral ER membrane protein with both N- and C-termini located in the cytosol (middle portions embedded in membrane, as shown by proteinase K protection). Loss of DAD1 function at non-permissive temperature causes a defect in N-linked glycosylation in tsBN7 cells, leading to apoptosis. Differential centrifugation; carbonate extraction; proteinase K digestion topology mapping; Western blot glycosylation analysis Genes to cells : devoted to molecular & cellular mechanisms High 9167970
1998 Loss of DAD1 (in tsBN7 cells at non-permissive temperature) destabilizes the entire OST complex: steady-state levels of OST48 become nearly undetectable and ribophorins are reduced ~50%, while other ER translocon components (TRAP α-subunit, Sec61) are unaffected. N-glycosylation of the ribophorins and a secretory glycoprotein is severely impaired, demonstrating that DAD1 is required for both structural integrity and enzymatic function of the OST complex. Western blot of cell lysates at permissive/non-permissive temperatures; pulse-chase glycosylation assay of secretory glycoprotein The Journal of biological chemistry High 9748289
2000 DAD1 interacts with Mcl-1 (a Bcl-2 family member) via a two-hybrid screen and co-immunoprecipitation in COS cells. The C-terminal domain of Mcl-1 containing the BH2 domain is required for interaction with DAD1, and the C-terminal half of DAD1 mediates binding. A ΔC-DAD1 mutant lacking 4 C-terminal residues fails to complement the tsBN7 mutation (cannot restore N-linked glycosylation) but retains Mcl-1 binding, indicating the DAD1 C-terminus is specifically required for OST function. Yeast two-hybrid screen; co-immunoprecipitation in COS cells; deletion mutagenesis; tsBN7 complementation assay Journal of biochemistry Medium 10965038
2000 Homozygous Dad1-null mouse embryos express abnormal N-glycosylated proteins and undergo increased apoptosis in specific tissues, are developmentally delayed by E7.5, exhibit impaired mesodermal development, fail to turn the posterior axis, and die by E10.5. This establishes that Dad1 is required in vivo for proper N-linked glycoprotein processing and for cell survival during mouse embryogenesis. Gene targeting (null allele); Western blot for N-glycoproteins; histological and TUNEL analysis of embryos Developmental biology High 10336695 10720432 10748466
2002 GFP-Dad1, when functionally incorporated into translocon complexes (TCs) in the ER, diffuses extremely slowly (Deff ~7-fold lower than free ER membrane proteins), as measured by FRAP, reflecting its assembly into large membrane-bound polysome arrays. Termination of protein synthesis increases GFP-Dad1 lateral mobility but not to the level of free protein, indicating DAD1/OST remains associated with inactive TCs after ribosome release. FRAP of GFP-Dad1 in live cells (tsBN7 rescue system); comparison to free ER membrane proteins; protein synthesis inhibition experiments The Journal of cell biology High 12163472
2012 Knockdown of DAD1 (or OST48) disrupts the assembly of both STT3A- and STT3B-containing OST complexes, causing pronounced hypoglycosylation of multiple substrates. Thus DAD1 is a global structural modulator required for the integrity and activity of both mammalian OST complexes. Subunit-specific siRNA knockdowns; analysis of OST complex assembly and enzymatic activity; glycosylation profiling Journal of cell science High 22467853
2024 DAD1 knockdown in neonatal rat cardiomyocytes impairs N-glycosylation of integrins α5 and β1, reduces focal adhesion kinase activation, impairs cell spreading and myofibrillogenesis, and induces anoikis (apoptosis from disrupted cell-matrix interaction). Enhancing cell adhesion (with adhesamine, fibronectin, or collagen IV) rescues cardiomyocyte death caused by Dad1 knockdown. Additionally, Dad1 and Stt3A (catalytic OST subunit) mutually stabilize each other's expression. siRNA knockdown in neonatal rat cardiomyocytes; caspase-3 cleavage assay; N-glycosylation assay of integrins; focal adhesion kinase activation assay; rescue with adhesion-promoting agents; cross-knockdown of Stt3A American journal of physiology. Cell physiology Medium 39611549
2006 In S. cerevisiae, the Gly58Arg mutation in Ost2p (corresponding to the apoptosis-causing Gly38Arg in hamster DAD1) causes temperature-sensitive growth arrest with decreased cell viability and phosphatidylserine exposure (apoptosis marker) at 37°C, without clear DNA fragmentation. High sorbitol rescues the temperature sensitivity, suggesting that ost2 mutant cell death is a secondary consequence of reduced protein N-linked glycosylation rather than a direct pro-apoptotic function. Site-directed mutagenesis (Gly58Arg, Gly86Arg, Glu113Val Ost2 alleles); growth and viability assays; phosphatidylserine exposure assay; DNA fragmentation assay; osmotic suppression with sorbitol Bioscience, biotechnology, and biochemistry Medium 16717427

Source papers

Stage 0 corpus · 40 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2007 DWARF10, an RMS1/MAX4/DAD1 ortholog, controls lateral bud outgrowth in rice. The Plant journal : for cell and molecular biology 393 17655651
1993 Molecular cloning of a human cDNA encoding a novel protein, DAD1, whose defect causes apoptotic cell death in hamster BHK21 cells. Molecular and cellular biology 188 8413235
1997 DAD1, the defender against apoptotic cell death, is a subunit of the mammalian oligosaccharyltransferase. Proceedings of the National Academy of Sciences of the United States of America 143 9144178
1996 Highly Branched Phenotype of the Petunia dad1-1 Mutant Is Reversed by Grafting. Plant physiology 122 12226274
1995 The essential OST2 gene encodes the 16-kD subunit of the yeast oligosaccharyltransferase, a highly conserved protein expressed in diverse eukaryotic organisms. The Journal of cell biology 103 7593165
1995 dad-1, an endogenous programmed cell death suppressor in Caenorhabditis elegans and vertebrates. The EMBO journal 90 7556086
2012 The oligosaccharyltransferase subunits OST48, DAD1 and KCP2 function as ubiquitous and selective modulators of mammalian N-glycosylation. Journal of cell science 78 22467853
2000 Mice lacking Dad1, the defender against apoptotic death-1, express abnormal N-linked glycoproteins and undergo increased embryonic apoptosis. Developmental biology 55 10720432
2002 Active translocon complexes labeled with GFP-Dad1 diffuse slowly as large polysome arrays in the endoplasmic reticulum. The Journal of cell biology 54 12163472
1998 DAD1 is required for the function and the structural integrity of the oligosaccharyltransferase complex. The Journal of biological chemistry 48 9748289
1997 The highly conserved DAD1 protein involved in apoptosis is required for N-linked glycosylation. Genes to cells : devoted to molecular & cellular mechanisms 46 9167970
1997 DAD1- and DAD2-like agonist effects on motor activity of C57 mice: differences compared to rats. Synapse (New York, N.Y.) 45 9097408
2001 Enhanced expression of mRNAs of antisecretory factor-1, gp96, DAD1 and CDC34 in human hepatocellular carcinomas. Biochimica et biophysica acta 43 11335099
2000 A subunit of the mammalian oligosaccharyltransferase, DAD1, interacts with Mcl-1, one of the bcl-2 protein family. Journal of biochemistry 40 10965038
2000 Deletion of Dad1 in mice induces an apoptosis-associated embryonic death. Genesis (New York, N.Y. : 2000) 38 10748466
1999 Abnormalities of developmental cell death in Dad1-deficient mice. Genes to cells : devoted to molecular & cellular mechanisms 38 10336695
1997 dad-1, A putative programmed cell death suppressor gene in rice. Plant & cell physiology 38 9150612
2004 Both CTCF-dependent and -independent insulators are found between the mouse T cell receptor alpha and Dad1 genes. The Journal of biological chemistry 37 15082712
1997 A targeted mutation at the T-cell receptor alpha/delta locus impairs T-cell development and reveals the presence of the nearby antiapoptosis gene Dad1. Molecular and cellular biology 36 9121464
2004 A tomato lipase homologous to DAD1 (LeLID1) is induced in post-germinative growing stage and encodes a triacylglycerol lipase. FEBS letters 28 15225633
1995 The highly conserved defender against the death 1 (DAD1) gene maps to human chromosome 14q11-q12 and mouse chromosome 14 and has plant and nematode homologs. FEBS letters 28 7737422
2007 A homologue of the defender against the apoptotic death gene (dad1 )in UV-exposed Chlamydomonas cells is downregulated with the onset of programmed cell death. Journal of biosciences 27 17435318
1999 Enhancer-blocking activity within the DNase I hypersensitive site 2 to 6 region between the TCR alpha and Dad1 genes. Journal of immunology (Baltimore, Md. : 1950) 26 10384128
2000 Glycosylation of phytepsin and expression of dad1, dad2 and ost1 during onset of cell death in germinating barley scutella. Mechanisms of development 23 10781951
1999 In vivo overexpression of Dad1, the defender against apoptotic death-1, enhances T cell proliferation but does not protect against apoptosis. Journal of immunology (Baltimore, Md. : 1950) 18 10438923
2021 Emerging role of BAD and DAD1 as potential targets and biomarkers in cancer. Oncology letters 17 34671425
2004 A homolog of the defender against apoptotic death gene (DAD1) in senescing gladiolus petals is down-regulated prior to the onset of programmed cell death. Journal of plant physiology 17 15602820
2003 cDNA cloning of a defender against apoptotic cell death 1 (DAD1) homologue, responsive to external temperature stimulus from the spider, Araneus ventricosus. Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology 16 12781979
2007 Down-regulation of defender against apoptotic death (DAD1) after yellow head virus (YHV) challenge in black tiger shrimp Penaeus monodon. Fish & shellfish immunology 15 18083552
2019 GmDAD1, a Conserved Defender Against Cell Death 1 (DAD1) From Soybean, Positively Regulates Plant Resistance Against Phytophthora Pathogens. Frontiers in plant science 13 30800138
2001 Function and factor interactions of a locus control region element in the mouse T cell receptor-alpha/Dad1 gene locus. Journal of immunology (Baltimore, Md. : 1950) 13 11564801
2024 Targeting DAD1 gene with CRISPR-Cas9 system transmucosally delivered by fluorinated polylysine nanoparticles for bladder cancer intravesical gene therapy. Theranostics 12 38164146
2018 Polymorphisms in the DAD1 and OXA1L genes are associated with asthma and atopy in a South American population. Molecular immunology 11 30032071
2007 Molecular cloning and responsive expression to injury stimulus of a defender against cell death 1 (DAD1) gene from bay scallops Argopecten irradians. Molecular biology reports 11 17294251
2006 Yeast cell death caused by mutation of the OST2 gene encoding the epsilon-subunit of Saccharomyces cerevisiae oligosaccharyltransferase. Bioscience, biotechnology, and biochemistry 7 16717427
2000 Molecular cloning of a homologue of dad-1 gene in citrus: distinctive expression during fruit development. Biochimica et biophysica acta 5 10786637
2024 Suppression of Dad1 induces cardiomyocyte death by weakening cell adhesion. American journal of physiology. Cell physiology 2 39611549
2024 New variants of the DAD1 and OXA1L genes are associated with asthma and atopy in an adult population. Gene 2 39615807
2010 The Dad1 subunit of the yeast kinetochore Dam1 complex is an intrinsically disordered protein. Biochemical and biophysical research communications 2 20727855
2024 ASPG and DAD1 are potential placental-derived biomarkers for ASD-like symptom severity levels in male/female offspring. Placenta 0 39154487

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