Affinage

FIZ1

Flt3-interacting zinc finger protein 1 · UniProt Q96SL8

Length
496 aa
Mass
52.0 kDa
Annotated
2026-06-09
13 papers in source corpus 8 papers cited in narrative 8 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

FIZ1 is a C2H2 zinc-finger protein that functions principally as a transcriptional co-regulator at photoreceptor-specific gene promoters in the maturing retina (PMID:12566383, PMID:18854042). It physically engages the rod transcription factor NRL through NRL's leucine zipper domain and the cone-rod homeobox factor CRX, integrating into the regulatory complexes assembled on Rhodopsin and Pde6b promoters in photoreceptors in vivo (PMID:12566383, PMID:18854042). Its transcriptional output is context-dependent: in heterologous cells FIZ1 represses NRL-driven activation of the rhodopsin promoter, yet it synergizes with NRL (and, for Rho, CRX) to activate rhodopsin and PDE6B reporters and enhances CRX-mediated activation of opsin promoters (PMID:12566383, PMID:17141759, PMID:18854042). FIZ1 protein abundance rises roughly ten-fold during postnatal retinal maturation, and its occupancy of the Rhodopsin promoter increases developmentally in parallel with the accumulation of transcriptionally active RNA Polymerase-II, placing FIZ1 within active promoter complexes of the mature neural retina (PMID:17141759, PMID:18854042, PMID:20161818). Beyond the retina, FIZ1 was originally identified as a binding partner of the catalytic domain of the receptor tyrosine kinase Flt3, an interaction independent of kinase activity and not shared with the related kinases Kit, Fms, or PDGFR (PMID:10409713). In keratinocytes, elevated FIZ1 accelerates G1/S progression and proliferation through MAP/ERK pathway activation and increased IGFBP3 secretion that enhances IGF1 signaling (PMID:24956037).

Mechanistic history

Synthesis pass · year-by-year structured walk · 8 steps
  1. 1999 Medium

    Established FIZ1 as a defined protein with a specific physical partner, answering what molecular context this previously uncharacterized zinc-finger protein operates in.

    Evidence Yeast two-hybrid screen and reciprocal in vitro/in vivo co-precipitation against the Flt3 receptor tyrosine kinase

    PMID:10409713

    Open questions at the time
    • Does not explain how a nucleocytoplasmic zinc-finger protein functions downstream of Flt3
    • No demonstration that the Flt3 interaction alters receptor signaling output
    • Functional consequence of the 11 zinc fingers unaddressed
  2. 2003 High

    Identified FIZ1 as a retinal transcription-factor partner, reframing it as a transcriptional regulator by showing it binds the NRL leucine zipper and represses NRL-driven rhodopsin transactivation.

    Evidence Y2H of retinal library, GST pulldown, Co-IP from bovine retinal nuclear extracts, reporter assays in CV1 cells

    PMID:12566383

    Open questions at the time
    • Repression shown only in heterologous CV1 cells, not native photoreceptors
    • Mechanism of repression (recruitment of corepressors, DNA contact) not defined
    • No CRX interaction tested at this stage
  3. 2006 Medium

    Linked FIZ1 to retinal maturation and revealed promoter-specific co-activation, showing its levels rise during development and that it synergizes with NRL (and conditionally CRX) on Rho and PDE6B promoters.

    Evidence Immunoblot, IHC, qPCR across P0–P21 mouse retina plus co-transfection reporter assays

    PMID:17141759

    Open questions at the time
    • Synergy demonstrated in reporter assays, not at endogenous loci
    • Mechanistic basis for the switch between repression and synergy unresolved
    • Single lab
  4. 2008 High

    Placed FIZ1 directly in promoter complexes in vivo, establishing CRX as a second partner and demonstrating developmental, Pol-II-correlated recruitment to active photoreceptor genes.

    Evidence Co-IP from retinal nuclear extracts, Y2H, GST pulldown, ChIP and quantitative ChIP, EMSA, reporter assays, immuno-EM in native retina

    PMID:18854042

    Open questions at the time
    • Whether FIZ1 contacts promoter DNA directly or only via NRL/CRX not resolved
    • Co-activator/corepressor machinery FIZ1 recruits unidentified
    • No loss-of-function phenotype in vivo
  5. 2010 Medium

    Generalized FIZ1's promoter association genome-wide, supporting its use as a marker of active mature-retina promoter complexes.

    Evidence ChIP-on-chip at 35 bp resolution across ~26,000 TSS in postnatal mouse retina

    PMID:20161818

    Open questions at the time
    • Correlative occupancy without functional perturbation
    • Direct vs indirect binding at most loci unclear
    • Single lab
  6. 2010 Low

    Extended FIZ1 into hematopoietic FLT3/IL-7 signaling, implicating it in STAT5A/c-Myc-driven B-lymphoblastic growth.

    Evidence Retroviral integration tagging in mouse B-LBLs with phospho-STAT5A/c-Myc Western blots and cytokine growth assays

    PMID:20360400

    Open questions at the time
    • Insertional-mutagenesis correlation with indirect readout; no direct mechanistic role for FIZ1 dissected
    • Cannot separate FIZ1 contribution from Stat5a integration cleanly
    • No biochemical link to FLT3 signaling shown
  7. 2014 Medium

    Defined a non-retinal proliferative function and broadened the interactome, showing FIZ1 drives keratinocyte G1/S progression via MAP/ERK and IGFBP3/IGF1 signaling.

    Evidence SILAC secretome, IGFBP3 antibody neutralization rescue, MAP/ERK inhibition, cell-cycle analysis, MS interactome mapping in HaCaT cells

    PMID:24956037

    Open questions at the time
    • Eight new interactors named only by category, mechanistic role untested
    • Connection between transcriptional and proliferative functions unclear
    • Single cell-line model
  8. 2024 Low

    Identified FIZ1 as a tractable target of targeted protein degradation, establishing it can be selectively eliminated by a small-molecule degrader.

    Evidence DegMS proteomic degradome analysis distinguishing primary degradation targets from downstream effects

    PMID:39536762

    Open questions at the time
    • No functional consequence of FIZ1 degradation characterized
    • Degron determinants and E3 ligase recruitment unspecified
    • No follow-up on FIZ1 biology

Open questions

Synthesis pass · forward-looking unresolved questions
  • How FIZ1 switches between repressing and co-activating the same transcription factors, and what corepressor/coactivator machinery it recruits at photoreceptor promoters, remains unresolved.
  • No structural model of FIZ1 with NRL or CRX
  • No in vivo loss-of-function retinal phenotype
  • Direct DNA-binding activity of the zinc fingers undemonstrated

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0140110 transcription regulator activity 3 GO:0003677 DNA binding 2
Localization
GO:0005634 nucleus 2 GO:0005829 cytosol 2
Pathway
R-HSA-74160 Gene expression (Transcription) 2 R-HSA-9709957 Sensory Perception 2
Partners
CRXFLT3NRL

Evidence

Reading pass · 8 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1999 FIZ1 (Flt3-interacting zinc-finger protein 1) was identified as a novel binding partner of the receptor tyrosine kinase Flt3, interacting specifically with Flt3's catalytic domain but not with the structurally related RTKs Kit, Fms, or PDGFR; this interaction is independent of kinase activity. FIZ1 contains 11 C2H2-type zinc fingers and the protein localizes to both nucleus and cytoplasm. Yeast two-hybrid screen, in vitro and in vivo co-precipitation assays, anti-Fiz1 antibody immunolocalization The Journal of biological chemistry Medium 10409713
2003 FIZ1 physically interacts with the leucine zipper domain of the rod photoreceptor transcription factor NRL (Neural Retina Leucine zipper) and acts as a repressor of NRL-mediated transactivation of the rhodopsin promoter, without affecting CRX-mediated transactivation. Yeast two-hybrid screening of retinal library, GST pulldown assay, co-immunoprecipitation from bovine retinal nuclear extracts, transient transfection reporter assays in CV1 cells Human molecular genetics High 12566383
2006 FIZ1 protein levels increase at least ten-fold during mouse neural retina maturation (P0 to P21+), and FIZ1 synergizes with NRL to activate transcription from rhodopsin (Rho) and PDE6B gene promoters in vitro. For the Rho promoter, synergistic activation requires both NRL and CRX, while for PDE6B, FIZ1 synergizes with NRL alone and CRX inclusion reduces this synergy. Immunoblotting, immunohistochemistry, quantitative real-time PCR, transient co-transfection reporter assays in CV1 cells Experimental eye research Medium 17141759
2008 FIZ1 directly interacts with CRX (Cone-Rod Homeobox) transcription factor and is part of the protein complex on several rod and cone gene promoters (including Rhodopsin and Pde6b) in photoreceptors in vivo. FIZ1 enhances CRX-mediated transcriptional activation of opsin gene promoters. The association of FIZ1 with the Rhodopsin promoter increases developmentally (P3 to P25) coinciding with increased transcriptionally active RNA Polymerase-II within the Rho gene. Co-immunoprecipitation from retinal nuclear extracts, yeast two-hybrid, GST pulldown, chromatin immunoprecipitation (ChIP) assays, electrophoretic mobility shift assays (EMSA) with FIZ1 antibody, quantitative ChIP, co-transfection reporter assays, transmission electron microscopy with nano-gold labeling BMC molecular biology High 18854042
2010 FIZ1 is part of the regulatory protein complex on active photoreceptor-specific gene promoters; ChIP-on-chip using FIZ1 as an additional ChIP marker highlighted genes activated in the mature neural retina, supporting a role for FIZ1 in active promoter complexes. Chromatin immunoprecipitation on chip (ChIP-on-chip) at 35 bp resolution across 26,000 gene transcription start sites in postnatal mouse retina Molecular vision Medium 20161818
2010 FIZ1 is involved in the IL-7/FLT3 signaling pathway in B lymphoblastic lymphomas; dual retroviral integration into Stat5a and Fiz1 loci led to increased phosphorylated STAT5A and c-Myc expression following FLT3 stimulation, and clones with both integrations grew faster in IL-7/FLT3L medium than clones with Stat5a integration alone. Retroviral integration tagging in mouse B-LBLs, Western blotting for phospho-STAT5A and c-Myc, growth assays in cytokine-supplemented medium Journal of leukocyte biology Low 20360400
2014 FIZ1 promotes proliferation of HaCaT keratinocytes via more rapid G1/S progression mediated by MAP/ERK kinase pathway activation; elevated FIZ1 levels increase expression and secretion of IGFBP3, enhancing IGF1 signaling sensitivity. Antibody-based neutralization of IGFBP3 abrogates the FIZ1-induced growth advantage. Interactome mapping identified eight novel FIZ1 binding partners in both cytoplasm and nucleus, including signal transduction factors, transcription factors, and NDR (Nuclear Dbf2-related) kinases. SILAC-based quantitative secretome analysis, antibody neutralization, MAP/ERK pathway inhibition, cell cycle analysis, quantitative interactome mapping (mass spectrometry-based) Journal of proteome research Medium 24956037
2024 FIZ1 (a zinc-finger protein) was identified as a direct degradation target of a small-molecule degrader, as determined by proteomic degradome analysis that distinguishes primary TPD targets from secondary downstream effects. DegMS (selective analysis of protein degradation by mass spectrometry at proteomic scale), excluding confounding effects of altered transcription/translation Cell chemical biology Low 39536762

Source papers

Stage 0 corpus · 13 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2003 Interaction of retinal bZIP transcription factor NRL with Flt3-interacting zinc-finger protein Fiz1: possible role of Fiz1 as a transcriptional repressor. Human molecular genetics 34 12566383
2005 Leukemia inhibitory factor blocks expression of Crx and Nrl transcription factors to inhibit photoreceptor differentiation. Investigative ophthalmology & visual science 33 15980254
1999 Fiz1, a novel zinc finger protein interacting with the receptor tyrosine kinase Flt3. The Journal of biological chemistry 24 10409713
2010 Temporal ChIP-on-Chip of RNA-Polymerase-II to detect novel gene activation events during photoreceptor maturation. Molecular vision 21 20161818
2008 FIZ1 is part of the regulatory protein complex on active photoreceptor-specific gene promoters in vivo. BMC molecular biology 17 18854042
2010 Dual retrovirus integration tagging: identification of new signaling molecules Fiz1 and Hipk2 that are involved in the IL-7 signaling pathway in B lymphoblastic lymphomas. Journal of leukocyte biology 13 20360400
2024 Degradome analysis to identify direct protein substrates of small-molecule degraders. Cell chemical biology 11 39536762
2006 FIZ1 is expressed during photoreceptor maturation, and synergizes with NRL and CRX at rod-specific promoters in vitro. Experimental eye research 8 17141759
2014 Dissection of a novel autocrine signaling pathway via quantitative secretome and interactome mapping. Journal of proteome research 6 24956037
2023 Depicting pseudotime-lagged causality across single-cell trajectories for accurate gene-regulatory inference. PNAS nexus 4 37113980
2021 Exploring Somatic Alteration Associating With Aggressive Behaviors of Papillary Thyroid Carcinomas by Targeted Sequencing. Frontiers in oncology 3 34692499
2026 Comprehensive machine learning and experimental verification reveal the mechanism of action of autophagy-related genes FIZ1 and FBXO21 in acute kidney injury. PeerJ 0 41660081
2025 Identification of candidate transcription factors that regulate Sox9 expression through the testis-specific enhancer in the Amami spiny rat Tokudaia osimensis, an XO/XO mammal. Genes & genetic systems 0 40467489

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