Affinage

DRC9

Dynein regulatory complex protein 9 · UniProt Q9H095

Length
443 aa
Mass
51.9 kDa
Annotated
2026-06-09
13 papers in source corpus 7 papers cited in narrative 7 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 5/5 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

IQCG (DRC9/CFAP122) is an IQ-motif-containing calmodulin (CaM)-binding protein that couples localized calcium signaling to microtubule-based structures in ciliated/flagellated cells and to haematopoiesis (PMID:24787902, PMID:24849454). It binds CaM through dual CaM-binding footprints in its IQ motif with higher affinity in the absence of calcium, and acts upstream of CaM-dependent kinase IV (CaMKIV); the structural and functional data support a model in which IQCG stores CaM at low calcium and releases it to activate CaMKIV when calcium rises, a step required for haematopoietic stem cell maintenance and multilineage differentiation (PMID:24787902). IQCG is essential for sperm flagellum formation: its loss causes male infertility with disorganized axonemes lacking the 9+2 microtubule arrangement and immotile sperm, and it localizes to the manchette in developing spermatids while binding CaM in a calcium-dependent manner in testis (PMID:24849454, PMID:24362311). Consistent with a conserved ciliary role, the Tetrahymena ortholog occupies the linker region of the nexin-dynein regulatory complex (N-DRC) in close contact with the CCDC96/113 complex (PMID:37714832). The leukemia-associated NUP98-IQCG fusion acts as an aberrant regulator that sequesters the export receptor CRM1, blocking nuclear export of the NF-κB subunit p65 and enhancing NF-κB activity, while also entrapping endogenous IQCG in the nucleus; the fusion stimulates proliferation and partially blocks differentiation of haematopoietic progenitors (PMID:18084320, PMID:27864780).

Mechanistic history

Synthesis pass · year-by-year structured walk · 6 steps
  1. 2007 Medium

    Established that the leukemia-associated NUP98-IQCG fusion is a functional transcriptional dysregulator, addressing how the fusion contributes to leukemogenesis.

    Evidence Co-IP, in vitro transcriptional assays, and differentiation/colony assays in 32Dcl3 and haematopoietic progenitor cells

    PMID:18084320

    Open questions at the time
    • Mechanism by which transcriptional activity is exerted not defined
    • Fusion alone insufficient to transform, leaving cooperating events unknown
    • No structural characterization of the fusion
  2. 2014 High

    Defined an essential, spermiogenesis-specific role for IQCG in axonemal 9+2 organization and sperm flagellum formation, linking it to CaM in vivo.

    Evidence Knockout/ENU mouse models with axoneme EM, manchette localization, CaM co-IP, and Chlamydomonas ortholog proteomics

    PMID:24362311 PMID:24849454

    Open questions at the time
    • Molecular function within the manchette/axoneme not resolved
    • Why tracheal and oviduct cilia are spared not explained
    • Direct biochemical activity of IQCG not defined
  3. 2014 High

    Resolved the structural basis of IQCG–CaM binding and placed IQCG upstream of CaMKIV in haematopoiesis, providing a CaM-storage/release model.

    Evidence Crystal structures of CaM–IQCG IQ-domain complexes, zebrafish morpholino loss-of-function, and biochemical binding assays

    PMID:24787902

    Open questions at the time
    • In vivo demonstration of CaM release driving CaMKIV activation incomplete
    • Connection between haematopoietic and flagellar roles unclear
    • Downstream CaMKIV targets in this context not mapped
  4. 2016 Medium

    Explained how NUP98-IQCG enhances NF-κB signaling, revealing a CRM1-sequestration mechanism distinct from wild-type IQCG calcium-dependent CaM binding.

    Evidence Co-IP with CRM1, nuclear export and NF-κB reporter assays, and subcellular fractionation

    PMID:27864780

    Open questions at the time
    • Single-lab Co-IP without structural validation
    • Calcium-independent CaM binding of fusion versus calcium-dependent wild-type binding not mechanistically reconciled
    • Contribution of p65 retention to leukemogenesis in vivo untested
  5. 2023 Medium

    Localized the DRC9 ortholog within the N-DRC linker region, positioning it structurally in the ciliary dynein regulatory machinery.

    Evidence Cryo-EM and integrative modeling with cross-linking in Tetrahymena thermophila

    PMID:37714832

    Open questions at the time
    • Single non-mammalian ciliate model
    • Functional consequence of DRC9 within N-DRC not tested by perturbation
    • Relationship to mammalian IQCG manchette/axoneme role not established
  6. 2024 Low

    Proposed a novel mitotic role for IQCG as a microtubule nucleation factor interacting with GSK3β, extending its function beyond cilia/flagella.

    Evidence Cell biology/centrosome assays, IQCG–GSK3β Co-IP, and evolutionary sequence analysis (preprint)

    PMID:bio_10.1101_2024.12.16.628806

    Open questions at the time
    • Preprint, not peer-reviewed
    • No reconstitution or structural validation of nucleation activity
    • Role of N2/GSK3β interaction in spindle function not mechanistically proven

Open questions

Synthesis pass · forward-looking unresolved questions
  • How IQCG's calcium/CaM-sensing function is mechanistically unified across haematopoiesis, sperm flagellum morphogenesis, and the N-DRC remains unresolved.
  • No single model links CaM storage/release to axonemal 9+2 assembly
  • Direct enzymatic or structural activity of IQCG within the axoneme/manchette undefined
  • Mitotic microtubule-nucleation role awaits peer-reviewed confirmation

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0008092 cytoskeletal protein binding 2 GO:0098772 molecular function regulator activity 1
Localization
GO:0005929 cilium 2 GO:0005634 nucleus 1
Pathway
R-HSA-1266738 Developmental Biology 2 R-HSA-162582 Signal Transduction 1
Partners
CALM1CAMKIVCCDC113CCDC96CRM1GSK3BNUP98
Complex memberships
nexin-dynein regulatory complex (N-DRC)

Evidence

Reading pass · 7 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2007 NUP98-IQCG fusion protein forms homodimers, heterodimerizes with NUP98 or IQCG, binds transcriptional co-activators and/or co-repressors, and shows transcriptional activity in vitro. Expression of NUP98-IQCG inhibits Ara-C-induced apoptosis in 32Dcl3 cells and partially blocks G-CSF-induced granulocyte differentiation. NUP98-IQCG stimulates proliferation and partially blocks differentiation of hematopoietic stem/progenitor cells but is insufficient alone to induce transformation. Co-immunoprecipitation, in vitro transcriptional assays, colony-forming and serial replating assays, cell differentiation assays Oncogene Medium 18084320
2014 IQCG (Iqcg) is required for sperm flagellum formation in mice; knockout causes male infertility with disorganized axonemes lacking the typical 9+2 microtubule arrangement and total sperm immobility. Iqcg localizes to the manchette in developing spermatids. Iqcg interacts with calmodulin in a calcium-dependent manner in the testis. Cilia in trachea and oviduct are unaffected, indicating a spermiogenesis-specific requirement. Gene knockout (targeted null allele), immunofluorescence/localization to manchette, co-immunoprecipitation with calmodulin, electron microscopy of axoneme ultrastructure PloS one High 24849454
2014 Loss of Iqcg in a forward genetic mouse screen disrupts spermiogenesis such that tail formation occurs incompletely or breaks apart from sperm heads (oligoasthenoteratospermia). The orthologous Chlamydomonas protein is present in flagella, consistent with a conserved role in flagellar formation/function. IQ motif-containing proteins typically regulate calmodulin, implicating localized calcium signaling in sperm flagellum morphogenesis. Forward genetic screen (ENU mutagenesis), targeted null allele confirmation, phylogenetic ortholog analysis, Chlamydomonas flagella proteomics G3 (Bethesda, Md.) High 24362311
2014 IQCG is required for haematopoietic stem cell maintenance and multilineage differentiation in zebrafish. Mechanistically, IQCG binds calmodulin (CaM) and acts upstream of CaM-dependent kinase IV (CaMKIV). Crystal structures of CaM–IQCG IQ domain complexes reveal dual CaM-binding footprints within the IQ motif and show that CaM–IQCG affinity is higher in the absence of calcium. The proposed model is that IQCG stores CaM at low calcium and releases it to activate CaMKIV when calcium rises. Zebrafish iqcg knockdown (morpholino), crystal structure of CaM–IQCG IQ domain complex, co-immunoprecipitation, biochemical binding assays Nature communications High 24787902
2016 NUP98-IQCG associates with the nuclear export receptor CRM1 and inhibits CRM1-mediated nuclear export of p65 (NF-κB subunit), thereby enhancing NF-κB transcriptional activity. NUP98-IQCG also entraps endogenous IQCG in the nucleus. The fusion protein interacts with calmodulin via its IQ motif in a calcium-independent manner. Co-immunoprecipitation (NUP98-IQCG with CRM1), nuclear export assays, NF-κB reporter/transcriptional activity assays, subcellular fractionation Frontiers of medicine Medium 27864780
2023 In the nexin-dynein regulatory complex (N-DRC) structure of Tetrahymena thermophila resolved by cryo-EM and integrative modeling, DRC9 (the ortholog of human DRC9/CFAP122) is localized in the linker region of the N-DRC, where it is in close contact with the CCDC96/113 complex. Cryo-electron microscopy, biochemical cross-linking, integrative structural modeling Nature communications Medium 37714832
2024 IQCG functions as a novel microtubule nucleation factor with dual roles: it promotes centrosomal microtubule organization during interphase and disperses into the spindle to promote microtubule generation during mitosis, ensuring robust cell division. IQCG interacts with GSK3β via its N2 region, which enhances centrosomal accumulation of IQCG in interphase. The IQCG gene has undergone accelerated evolution and positive selection in the human lineage, particularly in the variable N2 region. Genetic analyses, cell biological characterization (live imaging/centrosome assays), co-immunoprecipitation (IQCG–GSK3β), evolutionary sequence analysis bioRxivpreprint Low bio_10.1101_2024.12.16.628806

Source papers

Stage 0 corpus · 13 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2018 Identification and characterization of circular RNAs in Qinchuan cattle testis. Royal Society open science 44 30109096
2014 Iqcg is essential for sperm flagellum formation in mice. PloS one 38 24849454
2017 Widespread alternative exon usage in clinically distinct subtypes of Invasive Ductal Carcinoma. Scientific reports 37 28717182
2023 Integrated modeling of the Nexin-dynein regulatory complex reveals its regulatory mechanism. Nature communications 29 37714832
2014 IQ motif-containing G (Iqcg) is required for mouse spermiogenesis. G3 (Bethesda, Md.) 29 24362311
2007 A new fusion gene NUP98-IQCG identified in an acute T-lymphoid/myeloid leukemia with a t(3;11)(q29q13;p15)del(3)(q29) translocation. Oncogene 29 18084320
2021 Genotype-phenotype association and variant characterization in Diamond-Blackfan anemia caused by pathogenic variants in RPL35A. Haematologica 24 32241839
2014 Functional and molecular features of the calmodulin-interacting protein IQCG required for haematopoiesis in zebrafish. Nature communications 19 24787902
2021 Identification and Analysis of Potential Autophagy-Related Biomarkers in Endometriosis by WGCNA. Frontiers in molecular biosciences 12 34790699
2022 Further Insights on RNA Expression and Sperm Motility. Genes 11 35886074
2024 Dissecting the cell microenvironment of ovarian endometrioma through single-cell RNA sequencing. Science China. Life sciences 8 39470923
2016 Inhibition of the nuclear export of p65 and IQCG in leukemogenesis by NUP98-IQCG. Frontiers of medicine 6 27864780
2018 [Expression of IQCG in the human testis and its correlation with asthenospermia]. Zhonghua nan ke xue = National journal of andrology 4 30168948

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