Affinage

GADD45GIP1

Large ribosomal subunit protein mL64 · UniProt Q8TAE8

Length
222 aa
Mass
25.4 kDa
Annotated
2026-06-09
12 papers in source corpus 9 papers cited in narrative 9 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

GADD45GIP1 (CRIF1/CKBBP2) is a multifunctional protein with a central role in mitochondrial oxidative phosphorylation: tissue-specific knockout in mouse beta cells and adipocytes establishes it as essential for the synthesis and assembly of OxPhos complexes in the inner mitochondrial membrane, with its loss producing mitochondrial ultrastructural defects, glucose intolerance, and induction of the mitochondrial unfolded protein response with secretion of the mitokines GDF15 and FGF21 to regulate systemic energy homeostasis (PMID:25660120, PMID:31925461). In a cancer context, GADD45GIP1 is transcriptionally repressed by the BTB/POZ repressor NAC-1, and de-repression drives growth arrest and cellular senescence, so its NAC-1-mediated suppression underlies chemotherapy (paclitaxel and cisplatin) resistance in ovarian cancer cells (PMID:17804717, PMID:19305429, PMID:28599472). GADD45GIP1 physically associates with the beta subunit of protein kinase CKII and is phosphorylated at Ser221, with the phosphomimetic S221E form promoting proliferation (PMID:17069992, PMID:11710515). It also stabilizes the ribosomal protein RPL35 by inhibiting its ubiquitin-mediated degradation, thereby restraining the PERK/eIF2α ER stress pathway (PMID:40604925). The Drosophila ortholog stabilizes the RNase III enzyme Dicer-2 to support siRNA biogenesis and antiviral RNAi (PMID:25483042).

Mechanistic history

Synthesis pass · year-by-year structured walk · 9 steps
  1. 2001 Low

    Established the first physical partner of GADD45GIP1 (CKBBP2), mapping its interaction to a defined region of the CKII beta subunit and framing it as a CKII-associated protein.

    Evidence Yeast two-hybrid with interaction domain mapping to CKIIbeta residues 67–130

    PMID:11710515

    Open questions at the time
    • Single yeast two-hybrid approach with no orthogonal biochemical confirmation
    • Functional consequence of the interaction not addressed
    • Endogenous complex not demonstrated
  2. 2006 High

    Showed GADD45GIP1 is not just a CKII binder but a CKII substrate, defining Ser221 phosphorylation as a switch coupling the protein to cell proliferation.

    Evidence Yeast two-hybrid, pull-down, in vitro kinase assay, phosphoamino acid analysis, S221A/S221E mutagenesis and proliferation assays in COS7 cells

    PMID:17069992

    Open questions at the time
    • Downstream effectors of S221 phosphorylation not identified
    • Link between CKII phosphorylation and mitochondrial or transcriptional roles unresolved
  3. 2007 High

    Identified the transcriptional control point for GADD45GIP1, establishing NAC-1 as a repressor whose loss de-represses GADD45GIP1 to cause growth arrest, implicating it as a tumor suppressor.

    Evidence SAGE, shRNA knockdown and engineered overexpression of NAC-1 in SKOV3/HeLa with in vitro and in vivo growth assays

    PMID:17804717

    Open questions at the time
    • Direct promoter occupancy by NAC-1 not shown
    • Mechanism by which GADD45GIP1 enforces growth arrest unresolved
  4. 2009 Medium

    Connected GADD45GIP1 to chemoresistance and to the Gadd45 pathway, showing its level dictates paclitaxel sensitivity and that it interacts with Gadd45-gamma when NAC-1 repression is relieved.

    Evidence shRNA knockdown, ectopic expression, dominant-negative NAC-1, co-expression interaction studies and ex vivo drug resistance assays in ovarian cancer cells

    PMID:19305429

    Open questions at the time
    • Gadd45gamma interaction inferred rather than shown by direct reciprocal pulldown
    • Molecular basis of drug sensitivity not defined
  5. 2014 Medium

    Revealed a conserved gene-regulatory function via the ortholog, showing dCRIF stabilizes Dicer-2 to enable siRNA biogenesis and antiviral RNAi.

    Evidence Drosophila loss-of-function mutants, siRNA biogenesis and RNAi efficiency assays, antiviral immunity assays, Dicer-2 interaction/stabilization

    PMID:25483042

    Open questions at the time
    • Ortholog work in a non-mammalian system
    • Whether mammalian GADD45GIP1 has an analogous RNAi role untested
  6. 2015 High

    Defined the core in vivo function as mitochondrial, establishing CRIF1 as essential for OxPhos complex synthesis and assembly through a beta-cell-specific knockout with ultrastructural and metabolic failure.

    Evidence Conditional beta-cell-specific Crif1 knockout mice, glucose tolerance and insulin secretion assays, electron microscopy

    PMID:25660120

    Open questions at the time
    • Molecular step in OxPhos assembly catalyzed/scaffolded by CRIF1 not resolved
    • Relationship of mitochondrial role to its CKII and transcriptional functions unclear
  7. 2017 Medium

    Extended the NAC1–GADD45GIP1 axis to a senescence mechanism, showing GADD45GIP1 de-repression promotes cisplatin-induced senescence and cytotoxicity.

    Evidence RNAi and overexpression of NAC1, cisplatin cytotoxicity and beta-galactosidase senescence assays in two ovarian cancer lines

    PMID:28599472

    Open questions at the time
    • Single lab
    • Effectors linking GADD45GIP1 to the senescence program not identified
  8. 2020 High

    Showed the mitochondrial role drives systemic physiology, with adipocyte CRIF1 loss triggering the mitochondrial UPR and mitokine (GDF15/FGF21) secretion that protects against diet-induced obesity.

    Evidence Adipocyte-specific and double-knockout mice, high-fat diet, RNA-seq, doxycycline OxPhos inhibition in 3T3L1 cells, epistasis

    PMID:31925461

    Open questions at the time
    • Mechanism coupling OxPhos failure to mitokine induction not fully resolved
    • Cell-autonomous vs systemic contributions partly inferred
  9. 2025 Medium

    Added a cytoprotective protein-stabilization function, placing GADD45GIP1 upstream of RPL35 to restrain PERK/eIF2α ER stress.

    Evidence IP-LC-MS/MS interactome, knockdown/overexpression, ubiquitination and rescue assays, PERK/eIF2α readouts in osteosarcoma models

    PMID:40604925

    Open questions at the time
    • Single lab with conceptual concerns noted by commentators
    • Direct binding to RPL35 versus indirect stabilization not distinguished
    • How RPL35 stabilization integrates with the mitochondrial role unknown

Open questions

Synthesis pass · forward-looking unresolved questions
  • How GADD45GIP1's distinct activities—mitochondrial OxPhos assembly, CKII substrate/proliferation control, NAC1-regulated senescence, RPL35/ER-stress stabilization, and ortholog Dicer-2 stabilization—are integrated within one protein remains unresolved.
  • No structural model linking the binding surfaces for CKIIbeta, Gadd45gamma, RPL35, and OxPhos partners
  • Whether the mitochondrial and nuclear/cytosolic functions reflect distinct pools is unknown
  • No unifying biochemical mechanism connecting the cancer phenotypes to mitochondrial function

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0140313 molecular sequestering activity 2 GO:0140096 catalytic activity, acting on a protein 1
Pathway
R-HSA-1430728 Metabolism 2 R-HSA-5357801 Programmed Cell Death 2 R-HSA-8953897 Cellular responses to stimuli 2 R-HSA-8953854 Metabolism of RNA 1
Partners
CSNK2BDCR-2GADD45GNACC1RPL35

Evidence

Reading pass · 9 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2007 NAC-1, a BTB/POZ transcription repressor, negatively regulates GADD45GIP1 expression transcriptionally. NAC-1 knockdown in SKOV3 and HeLa cells induced GADD45GIP1 expression, while engineered NAC-1 expression in NAC-1-negative cells suppressed endogenous GADD45GIP1. Induced GADD45GIP1 expression caused growth arrest in vitro and in vivo, consistent with a tumor suppressor role. SAGE, shRNA knockdown, engineered overexpression, dominant-negative NAC-1, in vitro and in vivo growth assays Cancer research High 17804717
2009 Gadd45GIP1 interacts with Gadd45-gamma protein. NAC-1 homodimerization represses Gadd45GIP1, and Gadd45gamma interacts with Gadd45GIP1 when NAC-1 is disrupted. Knockdown of Gadd45GIP1 conferred paclitaxel resistance, while ectopic Gadd45GIP1 expression increased paclitaxel sensitivity in ovarian cancer cells. shRNA knockdown, ectopic expression, dominant-negative NAC-1, co-expression interaction studies, ex vivo drug resistance assays Oncogene Medium 19305429
2006 CKBBP2/CRIF1 (GADD45GIP1) physically associates with the beta subunit of protein kinase CKII in vitro and in vivo, and is phosphorylated by CKII at serine residue 221. Phosphomimetic mutant S221E promotes cell proliferation compared to wild-type or non-phosphorylatable S221A mutant. Yeast two-hybrid, pull-down assay, in vitro kinase assay with recombinant protein and purified CKII, phosphoamino acid analysis, site-directed mutagenesis (S221A and S221E), cell proliferation assays in COS7 cells Gene High 17069992
2001 GADD45GIP1 (CKBBP2) interacts with the CKIIbeta subunit. The minimal region of CKIIbeta required for interaction with CKBBP2 was mapped to residues 67–130. Yeast two-hybrid system, interaction domain mapping Molecules and cells Low 11710515
2015 CRIF1 (GADD45GIP1) is a mitochondrial protein essential for the synthesis and assembly of oxidative phosphorylation (OxPhos) complexes in the inner mitochondrial membrane. Beta-cell-specific Crif1 knockout mice exhibited progressive beta cell failure with mitochondrial ultrastructural abnormalities and severe glucose intolerance, establishing CRIF1 as required for mitochondrial OxPhos function in vivo. Conditional (beta-cell-specific) Crif1 knockout mouse model, glucose tolerance testing, insulin secretion assays, electron microscopy of mitochondrial ultrastructure Diabetologia High 25660120
2020 Adipocyte-specific deletion of Crif1 (GADD45GIP1) impairs adipocyte oxidative phosphorylation, triggering the mitochondrial unfolded protein response and increased secretion of mitokines GDF15 and FGF21, which regulate systemic energy homeostasis and protect against diet-induced obesity. GDF15 specifically regulated energy expenditure in AdKO mice. Adipocyte-specific Crif1 knockout mice (AdKO), high-fat diet challenge, RNA sequencing, doxycycline pharmacological OxPhos inhibition in 3T3L1 adipocytes, double-KO mice (AdGKO, AdFKO) for epistasis Diabetologia High 31925461
2014 Drosophila CRIF1 (dCRIF), the ortholog of mammalian GADD45GIP1, is required for RNAi pathway efficiency. Loss-of-function dCRIF mutants are deficient in siRNA biogenesis, RNAi-mediated gene knockdown, and antiviral immunity. dCRIF physically interacts with and stabilizes the RNase III enzyme Dicer-2. Drosophila genetic loss-of-function mutants, RNAi efficiency assays, siRNA biogenesis assays, antiviral immunity assays, interaction/stabilization studies with Dicer-2 RNA biology Medium 25483042
2017 NAC1 negatively regulates GADD45GIP1 to suppress cellular senescence, promoting cisplatin resistance. NAC1 knockdown increased GADD45GIP1 expression, inhibited cisplatin-induced senescence, and increased cisplatin cytotoxicity in SKOV3 cells. NAC1 overexpression in NAC1-negative TOV-21G cells reduced cisplatin sensitivity. RNAi knockdown of NAC1, plasmid-based NAC1 overexpression, cisplatin cytotoxicity assays, senescence assays (beta-galactosidase), in two ovarian cancer cell lines Oncology letters Medium 28599472
2025 GADD45GIP1 interacts with RPL35 and inhibits its ubiquitin-mediated proteasomal degradation. GADD45GIP1 knockdown decreased RPL35 protein stability and elevated RPL35 polyubiquitination. RPL35 knockdown activated the PERK/eIF2α pathway and increased ER stress, and RPL35 overexpression rescued the decrease in cell viability caused by GADD45GIP1 knockdown, placing GADD45GIP1 upstream of RPL35 in ER stress regulation. Immunoprecipitation combined with LC-MS/MS proteomics (263 interactors identified), GADD45GIP1 knockdown and overexpression, RPL35 knockdown, ubiquitination assays, PERK/eIF2α pathway readouts, rescue experiments, in vitro and in vivo osteosarcoma models Cancer cell international Medium 40604925

Source papers

Stage 0 corpus · 12 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2009 NAC-1, a potential stem cell pluripotency factor, contributes to paclitaxel resistance in ovarian cancer through inactivating Gadd45 pathway. Oncogene 72 19305429
1995 Use of reporter genes to identify recessive trans-acting mutations specifically involved in the regulation of Aspergillus nidulans penicillin biosynthesis genes. Journal of bacteriology 67 7677843
2007 NAC-1 controls cell growth and survival by repressing transcription of Gadd45GIP1, a candidate tumor suppressor. Cancer research 64 17804717
2020 An adipocyte-specific defect in oxidative phosphorylation increases systemic energy expenditure and protects against diet-induced obesity in mouse models. Diabetologia 57 31925461
2015 Disruption of CR6-interacting factor-1 (CRIF1) in mouse islet beta cells leads to mitochondrial diabetes with progressive beta cell failure. Diabetologia 22 25660120
2019 CRM197 reverses paclitaxel resistance by inhibiting the NAC-1/Gadd45 pathway in paclitaxel-resistant ovarian cancer cells. Cancer medicine 19 31490008
2006 Phosphorylation of CKBBP2/CRIF1 by protein kinase CKII promotes cell proliferation. Gene 11 17069992
2001 Mapping of the interaction domain of the protein kinase CKII beta subunit with target proteins. Molecules and cells 10 11710515
2017 Nucleus accumbens-1/GADD45GIP1 axis mediates cisplatin resistance through cellular senescence in ovarian cancer. Oncology letters 9 28599472
2014 Requirement for CRIF1 in RNA interference and Dicer-2 stability. RNA biology 5 25483042
2025 GADD45GIP1 promotes osteosarcoma progression by modulating RPL35 ubiquitination and alleviating endoplasmic reticulum stress via the PERK/eIF2α pathway. Cancer cell international 2 40604925
2026 Unresolved questions on the GADD45GIP1-RPL35 axis in osteosarcoma: mechanistic links to ER stress and therapeutic targeting. Cancer cell international 0 41606585

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