Affinage

DAD1

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

Length
113 aa
Mass
12.5 kDa
Annotated
2026-04-28
42 papers in source corpus 13 papers cited in narrative 13 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

DAD1 is a non-catalytic integral ER membrane subunit of the oligosaccharyltransferase (OST) complex that is essential for N-linked glycosylation, cell survival, and embryonic development. DAD1 co-sediments with OST activity in equimolar amounts with ribophorin I, ribophorin II, and OST48, directly contacting OST48 and ribophorin II, and is required for the assembly and stability of both STT3A- and STT3B-containing OST complexes; loss of DAD1 destabilizes OST48 and other subunits, causing pronounced hypoglycosylation of multiple substrates (PMID:9144178, PMID:9748289, PMID:22467853). In cardiomyocytes, DAD1 depletion impairs integrin N-glycosylation, inactivates focal adhesion kinase, and triggers anoikis that is rescued by enhanced cell adhesion, establishing that the apoptosis associated with DAD1 loss is a downstream consequence of defective glycosylation and disrupted cell-matrix interactions (PMID:39611549, PMID:16717427). Dad1-null mice die by E10.5 with aberrant N-glycoprotein processing, impaired mesodermal development, and increased apoptosis, and the anti-apoptotic function is conserved from C. elegans to mammals (PMID:10720432, PMID:7556086).

Mechanistic history

Synthesis pass · year-by-year structured walk · 10 steps
  1. 1993 High

    Identification of DAD1 as a gene whose loss triggers apoptosis established that this hydrophobic integral membrane protein has an essential cell-survival function independent of Bcl-2.

    Evidence DNA-mediated gene transfer complementation and temperature-shift assays in BHK21-derived tsBN7 cells

    PMID:8413235

    Open questions at the time
    • Molecular function unknown
    • Mechanism linking DAD1 loss to apoptosis not established
    • Subcellular localization not defined
  2. 1995 High

    Conservation of DAD1 function from yeast (OST2) to C. elegans to mammals established that DAD1 is an essential, evolutionarily conserved subunit of the OST complex with a cell-death-suppressive activity.

    Evidence Yeast OST2 disruption (lethal), in vitro OST activity assays, cross-species rescue in C. elegans and tsBN7 cells

    PMID:7556086 PMID:7593165

    Open questions at the time
    • Whether the anti-apoptotic role is direct or secondary to glycosylation defects
    • Physical association with mammalian OST not yet shown
  3. 1997 High

    Biochemical demonstration that DAD1 is a stoichiometric, tightly associated subunit of the mammalian OST complex, directly contacting OST48 and ribophorin II, answered how DAD1 fits into the glycosylation machinery.

    Evidence Sedimentation velocity analysis, radioiodination, and chemical crosslinking of purified OST and intact microsomes

    PMID:9144178 PMID:9167970

    Open questions at the time
    • Catalytic versus structural role within OST not resolved
    • Whether DAD1 loss reduces OST activity directly or by destabilizing other subunits
  4. 1998 High

    Showing that DAD1 loss destabilizes OST48 and ribophorins while inactivating OST activity established DAD1 as a structural scaffold essential for OST complex integrity.

    Evidence Western blotting and N-glycosylation assays of endogenous substrates after temperature shift in tsBN7 cells

    PMID:9748289

    Open questions at the time
    • Whether DAD1 directly stabilizes STT3 catalytic subunits not tested
    • Relationship between partial OST inactivation and apoptosis onset unclear
  5. 1999 Medium

    Dad1 heterozygous mice revealed haploinsufficiency phenotypes (syndactyly, thymic hypoplasia) and blastocyst studies suggested apoptosis may precede complete OST loss, raising the question of whether DAD1 has OST-independent functions.

    Evidence Gene targeting, heterozygote phenotyping, in vitro blastocyst culture with OST activity assays

    PMID:10336695

    Open questions at the time
    • OST activity measurements in dying cells may lack sensitivity
    • No direct evidence for an OST-independent anti-apoptotic mechanism
    • Haploinsufficiency phenotypes not replicated independently
  6. 2000 High

    Dad1-null embryonic lethality by E10.5 with aberrant glycoproteins and increased apoptosis proved in vivo essentiality, while DAD1-Mcl-1 physical interaction suggested a link between OST and anti-apoptotic Bcl-2 family signaling.

    Evidence Gene-targeted null mice with glycoprotein analysis; yeast two-hybrid and co-immunoprecipitation mapping DAD1-Mcl-1 interaction in COS cells

    PMID:10720432 PMID:10965038

    Open questions at the time
    • Functional significance of DAD1-Mcl-1 interaction for apoptosis regulation not demonstrated in vivo
    • Whether Mcl-1 binding is relevant to OST function unknown
  7. 2002 High

    Live-cell FRAP of functional GFP-Dad1 revealed that the OST-translocon assembly diffuses as large polysome-associated arrays in the ER membrane, establishing the supramolecular organization of the glycosylation machinery.

    Evidence FRAP in live cells with GFP-Dad1 (validated by tsBN7 rescue), protein synthesis inhibition experiments

    PMID:12163472

    Open questions at the time
    • Stoichiometry and composition of the polysome-OST-translocon supercomplex not defined
    • No structural data on DAD1 within the complex
  8. 2006 Medium

    Yeast ost2 Gly58Arg mutants showed that apoptosis-like cell death is a secondary consequence of glycosylation defects (rescued by sorbitol), arguing against a direct anti-apoptotic function for DAD1/Ost2p.

    Evidence Site-directed mutagenesis of OST2 in yeast, phosphatidylserine exposure assay, sorbitol osmotic rescue

    PMID:16717427

    Open questions at the time
    • Whether sorbitol rescue operates through glycosylation restoration or stress suppression not resolved
    • Yeast apoptosis-like death may not fully model mammalian apoptosis
  9. 2012 High

    Systematic siRNA depletion established that DAD1 (like OST48) is required for the stability and function of both STT3A and STT3B OST complexes, distinguishing it from accessory subunits like KCP2.

    Evidence siRNA knockdown with glycosylation assays and OST complex stability analysis in mammalian cells

    PMID:22467853

    Open questions at the time
    • Structural basis for DAD1's role in stabilizing both complexes unknown
    • Whether DAD1 has any catalytic contribution not tested
  10. 2024 High

    Identification of integrins as key DAD1-dependent glycosylation substrates, and rescue of DAD1-knockdown anoikis by enhanced adhesion, resolved a three-decade-old question by establishing that DAD1-associated apoptosis proceeds through defective integrin glycosylation, FAK inactivation, and loss of cell-matrix adhesion.

    Evidence siRNA knockdown in neonatal rat cardiomyocytes, integrin-specific glycosylation assays, FAK activity, rescue with adhesamine/fibronectin/collagen IV, DAD1-STT3A epistasis

    PMID:39611549

    Open questions at the time
    • Whether this integrin-FAK-anoikis mechanism generalizes beyond cardiomyocytes
    • Relative contribution of other underglycosylated substrates to cell death not assessed

Open questions

Synthesis pass · forward-looking unresolved questions
  • No high-resolution structural model of DAD1 within the mammalian OST complex exists, and the precise molecular contacts through which DAD1 stabilizes both STT3A and STT3B complexes remain undefined.
  • No cryo-EM or crystal structure of mammalian DAD1 in the OST complex
  • Functional significance of DAD1-Mcl-1 interaction in vivo remains untested
  • Whether DAD1 haploinsufficiency phenotypes reflect glycosylation thresholds or OST-independent roles is unresolved

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0005198 structural molecule activity 4
Localization
GO:0005783 endoplasmic reticulum 3
Pathway
R-HSA-392499 Metabolism of proteins 5 R-HSA-5357801 Programmed Cell Death 4
Partners
MCL1OST48RPN1RPN2STT3ASTT3B
Complex memberships
OST complex (STT3A-containing)OST complex (STT3B-containing)OST-translocon supercomplex

Evidence

Reading pass · 13 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 in BHK21-derived tsBN7 cells; a point mutation in DAD1 causes temperature-sensitive protein instability and apoptotic cell death that is inhibited by cycloheximide but not by Bcl-2. DNA-mediated gene transfer complementation, cDNA cloning, temperature-shift assay, protein analysis Molecular and cellular biology High 8413235
1997 DAD1 is a tightly associated subunit of the mammalian oligosaccharyltransferase (OST) complex, co-sedimenting with OST activity, ribophorin I, ribophorin II, and OST48 in roughly equimolar amounts; chemical crosslinking shows DAD1 directly contacts OST48 and ribophorin II within intact microsomes. 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 facing the cytosol; loss of DAD1 function causes a defect in N-linked glycosylation that leads to apoptosis in tsBN7 cells, whereas tunicamycin-induced glycosylation inhibition alone does not induce apoptosis. Differential centrifugation, carbonate extraction, proteinase K digestion topology assay, immunolocalization, N-glycosylation assay in tsBN7 cells Genes to cells : devoted to molecular & cellular mechanisms High 9167970
1998 Loss of DAD1 at the non-permissive temperature in tsBN7 cells destabilizes other OST subunits (OST48 reduced to barely detectable, ribophorins reduced ~50%) and inactivates OST activity, causing underglycosylation of ribophorins and secretory glycoproteins, without affecting Sec61 or TRAP complex levels. Western blot of OST subunits after temperature shift, N-glycosylation assays of endogenous substrates and secretory glycoproteins in tsBN7 cells The Journal of biological chemistry High 9748289
1995 The yeast DAD1 ortholog OST2 (Ost2p) is an essential subunit of the yeast OST complex; mutations in OST2 cause pleiotropic underglycosylation and reduced OST activity in vitro, and overexpression of Ost2p suppresses the temperature-sensitive wbp1-2 allele. Genomic disruption (lethality in haploid), conditional mutant analysis, in vitro OST activity assay, overexpression suppression, protein sequence analysis The Journal of cell biology High 7593165
1995 C. elegans Ce-dad-1 and human DAD1 are functionally interchangeable: overexpression of either under a heat-shock promoter suppresses developmentally programmed cell death in C. elegans embryos, and Ce-dad-1 rescues tsBN7 hamster cells from apoptosis as efficiently as vertebrate DAD1. Transgenic C. elegans overexpression (heat-shock promoter), scoring of PCD corpses, tsBN7 cell complementation assay The EMBO journal High 7556086
2000 Dad1-null mouse embryos (generated by gene targeting) express abnormal N-glycosylated proteins, are developmentally delayed by E7.5, show impaired mesodermal development, increased apoptosis in specific tissues, and die by E10.5, demonstrating that Dad1 is required in vivo for proper N-linked glycoprotein processing and cell survival. Gene targeting (null allele), glycoprotein analysis, embryo phenotyping, apoptosis assays Developmental biology High 10720432
2000 DAD1 interacts with Mcl-1 (a Bcl-2 family member) via the BH2-containing C-terminal domain of Mcl-1 and the C-terminal half of DAD1, as shown by yeast two-hybrid and co-immunoprecipitation in COS cells; a DAD1 mutant lacking only 4 C-terminal residues cannot complement the tsBN7 mutation despite retaining Mcl-1 binding, indicating the C-terminus of DAD1 is critical for N-glycosylation function. Yeast two-hybrid, co-immunoprecipitation in COS cells, deletion mutagenesis, tsBN7 complementation assay Journal of biochemistry Medium 10965038
2002 GFP-Dad1, functionally incorporated into the translocon complex (TC) within rough ER, diffuses ~7-fold more slowly than free ER membrane proteins as measured by FRAP; termination of protein synthesis increases GFP-Dad1 lateral mobility, indicating that the OST-TC assembly is stabilized within membrane-bound polysome arrays. GFP-tagging, FRAP in live cells, tsBN7 complementation (functional rescue), protein synthesis inhibition experiments The Journal of cell biology High 12163472
2012 OST48 and DAD1 are each required for the assembly and stability of both STT3A- and STT3B-containing OST complexes in mammalian cells; depletion of either subunit by siRNA knockdown causes pronounced hypoglycosylation of multiple substrates, whereas KCP2 depletion selectively affects co-translational substrates of the STT3A complex. siRNA knockdown, glycosylation assays, OST complex stability analysis (subunit-specific depletion) Journal of cell science High 22467853
1999 Dad1 heterozygous mice show soft-tissue syndactyly and mild thymic hypoplasia, indicating a role in developmental apoptosis; in vitro blastocyst culture of Dad1-null cells shows apoptotic abnormalities, yet oligosaccharyltransferase activity appears retained in dying cells, suggesting apoptosis induction precedes complete OST loss. Gene targeting, in vitro blastocyst culture, OST activity assay, phenotypic analysis of heterozygotes Genes to cells : devoted to molecular & cellular mechanisms Medium 10336695
2024 Dad1 knockdown in neonatal rat cardiomyocytes (NRCMs) impairs N-glycosylation of integrins α5 and β1, inactivates focal adhesion kinase, disrupts cell spreading and myofibrillogenesis, and induces anoikis (apoptosis via disrupted cell-matrix interactions); this is rescued by enhanced cell adhesion (adhesamine, fibronectin, collagen IV). Dad1 and STT3A (catalytic OST subunit) mutually stabilize each other within the OST complex. siRNA knockdown, N-glycosylation assays of specific integrin substrates, cell viability and caspase-3 assays, focal adhesion kinase activity, rescue with adhesion substrates, co-depletion epistasis (Dad1/Stt3A) American journal of physiology. Cell physiology High 39611549
2006 Yeast ost2 mutants carrying the Gly58Arg mutation (equivalent to the apoptosis-causing Gly38Arg in hamster DAD1) show temperature-sensitive growth arrest, phosphatidylserine exposure (apoptosis marker), and overall reduced N-linked glycosylation; sorbitol supplementation rescues temperature sensitivity, indicating apoptosis-like death is a secondary consequence of glycosylation defects. Site-directed mutagenesis of OST2 in yeast, growth assays, phosphatidylserine exposure assay, sorbitol rescue Bioscience, biotechnology, and biochemistry Medium 16717427

Source papers

Stage 0 corpus · 42 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 390 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 77 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
2014 Wound-induced expression of DEFECTIVE IN ANTHER DEHISCENCE1 and DAD1-like lipase genes is mediated by both CORONATINE INSENSITIVE1-dependent and independent pathways in Arabidopsis thaliana. Plant cell reports 23 24430866
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
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
2021 Emerging role of BAD and DAD1 as potential targets and biomarkers in cancer. Oncology letters 15 34671425
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 11 38164146
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
2018 Polymorphisms in the DAD1 and OXA1L genes are associated with asthma and atopy in a South American population. Molecular immunology 10 30032071
2019 Investigation of the interaction of DAD1-LIKE LIPASE 3 (DALL3) with Selenium Binding Protein 1 (SBP1) in Arabidopsis thaliana. Plant science : an international journal of experimental plant biology 9 31928671
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
2010 The Dad1 subunit of the yeast kinetochore Dam1 complex is an intrinsically disordered protein. Biochemical and biophysical research communications 2 20727855
2024 New variants of the DAD1 and OXA1L genes are associated with asthma and atopy in an adult population. Gene 1 39615807
2024 ASPG and DAD1 are potential placental-derived biomarkers for ASD-like symptom severity levels in male/female offspring. Placenta 0 39154487