Affinage

SYCP3

Synaptonemal complex protein 3 · UniProt Q8IZU3

Length
236 aa
Mass
27.7 kDa
Annotated
2026-06-10
36 papers in source corpus 15 papers cited in narrative 15 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 7/8 claims corpus-supported (88%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

SYCP3 is the principal structural protein of the synaptonemal complex lateral element that organizes and compacts meiotic chromosomes during prophase I (PMID:24950965, PMID:15237206). It forms a highly elongated, ~20 nm helical tetramer whose intrinsically disordered N-terminal tails project from each end of a rod-like core and bind double-stranded DNA, allowing a single molecule to bridge distant sites along the chromatid; this DNA-bridging activity has been directly visualized at the single-molecule level and provides the physical basis for chromosome compaction (PMID:24950965, PMID:28287952). SYCP3 self-assembles into flexible higher-order fibres through interactions between its disordered tails rather than its helical cores, with the conserved central alpha-helix and flanking CM1/CM2 motifs necessary and sufficient for polymerization (PMID:31615332, PMID:18391527). Functionally, SYCP3 is required for intimate synapsis of homologous chromosome cores and for the specificity of chromatin-loop attachment to the core, and it maintains cohesin-core integrity at diplotene in a sex-specific manner, with female chromosomes losing cohesin prematurely in its absence (PMID:15870106, PMID:15237206). Genome-wide it occupies open chromatin and SINE repeats, with its occupancy facilitated by transcription and fibre assembly and largely encompassing the cohesin-rich regions also bound by SYCP1 (PMID:40488283). SYCP3 abundance is controlled at the translational level by DAZL during spermatogenesis and post-translationally by FBXW24-mediated ubiquitination, which drives its timely degradation during pachytene to permit normal DSB repair and crossover formation (PMID:17526644, PMID:35858239). Dominant-negative C-terminal SYCP3 mutations that disrupt fibre formation cause azoospermia in men and recurrent pregnancy loss in women (PMID:14643120, PMID:19110213). When aberrantly expressed in mitotic cells, SYCP3 forms a complex with BRCA2 and impairs RAD51-mediated homologous recombination, conferring PARP-inhibitor sensitivity and chromosomal instability (PMID:22116401).

Mechanistic history

Synthesis pass · year-by-year structured walk · 11 steps
  1. 2003 Medium

    Established that the SYCP3 C-terminal coiled-coil is essential for fibre assembly and that its disruption causes human disease, linking protein self-assembly to fertility.

    Evidence Patient gene sequencing plus in vitro interaction and cell-based fibre formation assays of a truncating (643delA) mutant

    PMID:14643120

    Open questions at the time
    • Dominant-negative mechanism inferred from a single patient context
    • Structural basis of the C-terminal interaction not resolved
  2. 2004 Medium

    Distinguished SYCP3's role in synapsis from homology recognition and revealed it confers specificity to chromatin-loop attachment, defining its architectural function on the chromosome core.

    Evidence Whole chromosome painting and loop-size measurements in Sycp3-/- male mice

    PMID:15237206

    Open questions at the time
    • Molecular basis of loop-attachment specificity unresolved
    • Male-only analysis
  3. 2005 High

    Showed SYCP3 maintains rather than establishes cohesin-core organization, and does so sex-specifically, explaining a female-biased meiotic vulnerability.

    Evidence Cohesin immunostaining in Sycp3-deficient mouse germ cells

    PMID:15870106

    Open questions at the time
    • Mechanism of the male/female difference unknown
    • Direct SYCP3-cohesin interaction not demonstrated
  4. 2007 Medium

    Defined the conserved domains sufficient for polymerization and demonstrated deep evolutionary conservation of the assembly mechanism, while linking SYCP3 to translational control and achiasmate sex-chromosome segregation.

    Evidence Domain-deletion and cross-species co-assembly EM/fractionation, DAZL RNA-binding/translation/KO assays, and meiotic-spread immunolocalization in gerbil

    PMID:17459791 PMID:17526644 PMID:17983272 PMID:18391527

    Open questions at the time
    • High-resolution structure of the polymerization interface not defined
    • DAZL regulation shown only in male germ cells
    • Sex-chromosome bridging role observed in a single species
  5. 2008 Medium

    Extended the disease link to female reproductive failure, showing dominant-negative SYCP3 splice/C-terminal mutants impair fibre formation in recurrent pregnancy loss.

    Evidence Minigene splicing, in vitro interaction, and heterologous co-expression fibre assays from patient mutations

    PMID:19110213

    Open questions at the time
    • In vivo meiotic consequence in patients not directly observed
    • Penetrance and causality at population level not established
  6. 2011 Medium

    Revealed a pathological gain-of-function: aberrant somatic SYCP3 expression sequesters BRCA2 to suppress homologous recombination and drive genome instability.

    Evidence Co-IP of SYCP3-BRCA2, HR pathway and PARP-inhibitor viability assays, and chromosomal instability measurement in mitotic cells

    PMID:22116401

    Open questions at the time
    • Co-IP without reciprocal/structural validation of the SYCP3-BRCA2 interface
    • Physiological relevance in tumors not established
  7. 2014 High

    Provided the structural mechanism: a ~20 nm helical tetramer with DNA-binding N-terminal tails at each end that bridges distant DNA sites and self-assembles into lateral-element-like fibres.

    Evidence Crystal structure with DNA-binding and in vitro self-assembly/EM validation

    PMID:24950965

    Open questions at the time
    • N-terminal tails are disordered and not fully resolved
    • How tetramers organize into the ordered SC lattice not shown
  8. 2017 High

    Directly visualized SYCP3-mediated DNA bridging and compaction at single-molecule resolution, confirming the strut-like compaction model.

    Evidence Single-molecule optical tweezers with fluorescence microscopy plus bulk biochemistry

    PMID:28287952

    Open questions at the time
    • In vitro reconstitution does not capture chromatin context
    • Cooperation with cohesin/other SC proteins not addressed
  9. 2019 High

    Resolved the higher-order fibre architecture, showing irregular, tail-driven assembly with no helical-core contacts that yields a flexible DNA-engaging fibre.

    Evidence Cryo-electron tomography and atomic force microscopy of SYCP3 fibres

    PMID:31615332

    Open questions at the time
    • In vivo fibre geometry within the SC not confirmed
    • Contribution of partner proteins to fibre order unknown
  10. 2022 High

    Identified post-translational control of SYCP3, showing FBXW24 ubiquitinates it for timely pachytene degradation required for DSB repair and crossover formation.

    Evidence Co-IP/immuno-EM, MS site mapping, in vitro/in vivo ubiquitination assays, and Fbxw24-KO mouse phenotyping

    PMID:35858239

    Open questions at the time
    • How elevated SYCP3 mechanistically impairs DSB repair not fully resolved
    • Whether degradation is regionally restricted on chromosomes unknown
  11. 2025 Medium

    Mapped genome-wide SYCP3 occupancy, linking its chromatin binding to open regions, SINE repeats, transcription, fibre assembly, and cohesin/SYCP1 co-occupancy.

    Evidence Chromatin occupancy profiling (ChIP/CUT&RUN equivalent) with SYCP1 co-occupancy analysis in mouse spermatocytes

    PMID:40488283

    Open questions at the time
    • Causal direction between transcription and occupancy not established
    • Functional consequence of SINE enrichment unknown

Open questions

Synthesis pass · forward-looking unresolved questions
  • How SYCP3's in vitro DNA-bridging tetramers, cohesin maintenance, and genome-wide occupancy integrate into the ordered three-dimensional lateral element within the intact meiotic chromosome remains unresolved.
  • No in vivo structure of the assembled lateral element
  • Direct biochemical link between SYCP3 and cohesin not defined
  • Determinants of loop-attachment specificity unidentified

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0003677 DNA binding 3 GO:0005198 structural molecule activity 3
Localization
GO:0005694 chromosome 4 GO:0000228 nuclear chromosome 2
Pathway
R-HSA-1474165 Reproduction 3 R-HSA-1640170 Cell Cycle 2 R-HSA-73894 DNA Repair 2
Complex memberships
synaptonemal complex lateral element

Evidence

Reading pass · 15 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2014 Human SYCP3 forms a highly-elongated helical tetramer of ~20 nm length. N-terminal sequences extending from each end of the rod-like structure bind double-stranded DNA, enabling SYCP3 to bridge distant sites along the sister chromatid. SYCP3 self-assembles into regular filamentous structures resembling the SC lateral element morphology. Protein crystallography/structural determination combined with DNA-binding assays and in vitro self-assembly/electron microscopy eLife High 24950965
2017 SYCP3 mediates chromosome compaction by bridging distant DNA sites via DNA-binding domains at each end of its strut-like tetrameric structure, directly visualized at the single-molecule level using optical tweezers and fluorescence microscopy. Single-molecule optical tweezers combined with fluorescence microscopy and microfluidics, plus bulk biochemical assays eLife High 28287952
2019 The three-dimensional architecture of the SYCP3 fibre is built on a highly irregular arrangement of SYCP3 molecules with limited local geometry; interactions between molecules are driven by intrinsically disordered tails with no contact between helical cores, resulting in a flexible fibre. The fibre engages in extensive interactions with DNA. Cryo-electron tomography and atomic force microscopy Open biology High 31615332
2003 A truncating mutation (643delA) in SYCP3 that removes the C-terminal coiled-coil region produces a mutant protein with greatly reduced interaction with wild-type SYCP3 in vitro and interferes with SYCP3 fibre formation in cultured cells, acting as a dominant-negative to cause azoospermia. In vitro protein interaction assay (co-expression/pulldown), cell-based fibre formation assay, SYCP3 gene sequencing in patients Lancet Medium 14643120
2008 Two heterozygous SYCP3 mutations found in women with recurrent pregnancy loss affect normal splicing and produce C-terminally mutated proteins that interact with wild-type SYCP3 in vitro and inhibit normal SYCP3 fibre formation when co-expressed in a heterologous system, acting in a dominant-negative manner. Minigene splicing assay, in vitro protein interaction assay, heterologous cell co-expression fibre formation assay American journal of human genetics Medium 19110213
2011 SYCP3 forms a complex with BRCA2 and inhibits BRCA2's role in homologous recombination (HR), thereby impairing RAD51-mediated HR, inducing hypersensitivity to PARP inhibitors, and causing chromosomal instability in mitotic cells. Co-immunoprecipitation to establish SYCP3–BRCA2 complex; HR pathway assay; cell viability assay with PARP inhibitor; chromosomal instability measurement EMBO reports Medium 22116401
2005 In the absence of SYCP3, cohesin cores associated with female (but not male) meiotic chromosomes disassemble prematurely at the diplotene stage, demonstrating that SYCP3 is required for maintaining (but not establishing) cohesin-core organization during prophase I in a sex-specific manner. Analysis of cohesin protein distribution by immunostaining in Sycp3-deficient mouse germ cells (knockout mouse model) Journal of cell science High 15870106
2004 SYCP3 (and SYCP2) are required for intimate synapsis of homologous chromosome cores but not for homology-based alignment (which appears mediated by chromatin-chromatin interactions). Additionally, SYCP3/SYCP2 provide specificity for chromatin loop attachment to the chromosome core, as their absence leads to anomalous attachment of exogenous sequences. Whole chromosome painting in Sycp3-/- male mice; chromatin loop size measurement using satellite and transgene sequences in knockout vs. wild-type Cytogenetic and genome research Medium 15237206
2007 DAZL binds to Sycp3 mRNA and enhances its translation in male mouse germ cells; in Dazl knockout mice, SYCP3 protein levels are decreased, establishing Sycp3 as a biologically relevant target of Dazl-mediated translational regulation during spermatogenesis. RNA binding assay (DAZL–Sycp3 mRNA interaction), in vitro translation assay, Western blot analysis of SYCP3 protein in Dazl knockout mice RNA High 17526644
2022 The E3 ubiquitin ligase substrate receptor FBXW24 directly binds and ubiquitinates SYCP3 to regulate its stability and timely degradation during pachytene. Fbxw24-KO females show elevated SYCP3 levels, delayed meiotic prophase progression, increased DSBs, decreased crossover foci, and infertility. Key ubiquitination sites on SYCP3 were mapped by mass spectrometry and confirmed by in vitro and in vivo ubiquitination assays. Co-IP and immuno-EM (FBXW24–SYCP3 interaction); mass spectrometry (ubiquitination site mapping); in vivo and in vitro ubiquitination assays; Fbxw24-KO mouse phenotypic analysis (fertility, DSB markers, crossover foci) Clinical and translational medicine High 35858239
2007 The evolutionarily conserved domains of SYCP3 (the central alpha-helix together with flanking motifs CM1 and CM2) are necessary and sufficient for SYCP3 polymerization into higher-order structures, as shown for rat SYCP3. Deletion of the very end of the alpha-helix and CM2 disrupts polymerization and is associated with meiotic disruption. Immunocytochemistry, electron microscopy, and cell fractionation of SYCP3 domain deletion constructs Sexual development Medium 18391527
2007 Despite ~450 million years of sequence divergence, rat and medaka fish SYCP3 orthologs share conserved polymerization properties and can co-assemble into higher-order structures, as demonstrated by immunocytochemistry, electron microscopy, and cell fractionation. Immunocytochemistry, electron microscopy, cell fractionation of co-expressed rat and medaka SYCP3 Biochimica et biophysica acta Medium 17459791
2007 SYCP3 forms an intricate network structure from diplotene onwards on achiasmate sex chromosomes in Mongolian gerbil, maintaining sex chromosome association through metaphase I, with SYCP3 filaments connecting X and Y chromosomes observed during anaphase I segregation. This implicates SYCP3 in the segregation of sex chromosomes that lack pseudoautosomal recombination. Immunolocalization of SYCP3 (and SYCP1, RAD51, MLH1, γ-H2AX) on meiotic chromosome spreads across meiotic stages PLoS genetics Medium 17983272
2025 Genome-wide chromatin occupancy profiling shows SYCP3 is enriched at open chromatin regions and specific SINE repeats in mouse spermatocytes. SYCP3 occupancy is largely inherited from leptotene to pachytene, is facilitated by transcription and fibrous assembly, and SYCP1-occupied regions are largely a subpopulation of SYCP3-occupied regions with high cohesin enrichment. ChIP-seq / chromatin occupancy profiling (CUT&RUN or equivalent) in mouse spermatocytes combined with SYCP1 co-occupancy analysis Nucleic acids research Medium 40488283
2001 The putative promoter of SYCP3 was cloned and shown to drive transcription of a reporter gene in somatic cells, establishing the basic transcriptional regulatory element of the gene. Reporter gene (transcriptional) assay in somatic cells Biochimica et biophysica acta Low 11311943

Source papers

Stage 0 corpus · 36 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2003 Azoospermia in patients heterozygous for a mutation in SYCP3. Lancet (London, England) 207 14643120
2014 A molecular model for the role of SYCP3 in meiotic chromosome organisation. eLife 122 24950965
2007 Translation of the synaptonemal complex component Sycp3 is enhanced in vivo by the germ cell specific regulator Dazl. RNA (New York, N.Y.) 100 17526644
2005 SYCP2 and SYCP3 are required for cohesin core integrity at diplotene but not for centromere cohesion at the first meiotic division. Journal of cell science 83 15870106
2011 Evaluation of Sycp3, Plzf and Cyclin B3 expression and suitability as spermatogonia and spermatocyte markers in zebrafish. Gene expression patterns : GEP 81 21402175
2008 Mutations of the SYCP3 gene in women with recurrent pregnancy loss. American journal of human genetics 69 19110213
2007 Meiotic pairing and segregation of achiasmate sex chromosomes in eutherian mammals: the role of SYCP3 protein. PLoS genetics 69 17983272
2009 The multi-copy mouse gene Sycp3-like Y-linked (Sly) encodes an abundant spermatid protein that interacts with a histone acetyltransferase and an acrosomal protein. Biology of reproduction 55 19176879
2006 Structural components of the synaptonemal complex, SYCP1 and SYCP3, in the medaka fish Oryzias latipes. Experimental cell research 55 16764855
2010 Deficiency in the multicopy Sycp3-like X-linked genes Slx and Slxl1 causes major defects in spermatid differentiation. Molecular biology of the cell 50 20739462
2011 Synaptonemal complex protein SYCP3 impairs mitotic recombination by interfering with BRCA2. EMBO reports 41 22116401
2004 Male mouse meiotic chromosome cores deficient in structural proteins SYCP3 and SYCP2 align by homology but fail to synapse and have possible impaired specificity of chromatin loop attachment. Cytogenetic and genome research 41 15237206
2007 Expression of two testis-specific genes, TSGA10 and SYCP3, in different cancers regarding to their pathological features. Cancer detection and prevention 37 17920210
2011 Differential mRNA expression and promoter methylation status of SYCP3 gene in testes of yaks and cattle-yaks. Reproduction in domestic animals = Zuchthygiene 36 22497622
2006 Testicular expression of synaptonemal complex protein 3 (SYCP3) messenger ribonucleic acid in 110 patients with nonobstructive azoospermia. Fertility and sterility 36 16824523
2017 Single-molecule observation of DNA compaction by meiotic protein SYCP3. eLife 33 28287952
2005 SYCP3 mutations are uncommon in patients with azoospermia. Fertility and sterility 32 16213863
2007 Synaptonemal complex protein SYCP3: Conserved polymerization properties among vertebrates. Biochimica et biophysica acta 29 17459791
2007 Synaptonemal complex protein SYCP3 of the rat: evolutionarily conserved domains and the assembly of higher order structures. Sexual development : genetics, molecular biology, evolution, endocrinology, embryology, and pathology of sex determination and differentiation 22 18391527
2014 The T657C polymorphism on the SYCP3 gene is associated with recurrent pregnancy loss. Journal of assisted reproduction and genetics 20 25059562
2013 SYCP3-like X-linked 2 is expressed in meiotic germ cells and interacts with synaptonemal complex central element protein 2 and histone acetyltransferase TIP60. Gene 20 23810942
2001 The genomic structure of SYCP3, a meiosis-specific gene encoding a protein of the chromosome core. Biochimica et biophysica acta 20 11311943
2011 Characterization of a novel mouse gene encoding an SYCP3-like protein that relocalizes from the XY body to the nucleolus during prophase of male meiosis I. Biology of reproduction 17 21451147
2019 Molecular architecture of the SYCP3 fibre and its interaction with DNA. Open biology 14 31615332
2012 Investigation of mutations in the synaptonemal complex protein 3 (SYCP3) gene among azoospermic infertile male patients in the Turkish population. Andrologia 14 22670862
2011 SYCP3 mutation may not be associated with recurrent miscarriage caused by aneuploidy. Human reproduction (Oxford, England) 14 21357605
2010 Synaptonemal complex protein SYCP3 exists in two isoforms showing different conservation in mammalian evolution. Cytogenetic and genome research 14 20339291
2012 Mutation screening of AURKB and SYCP3 in patients with reproductive problems. Molecular human reproduction 13 23100464
2022 FBXW24 controls female meiotic prophase progression by regulating SYCP3 ubiquitination. Clinical and translational medicine 12 35858239
2011 Absence of SYCP3 mutations in women with recurrent miscarriage with at least one trisomic miscarriage. Reproductive biomedicine online 12 22197129
2013 Analysis of SYCP3 encoding synaptonemal complex protein 3 in human aneuploidies. Archives of gynecology and obstetrics 6 23677416
2019 Histochemical Study of the Emergence of Apoptosis and Altered SYCP3 Protein Distribution During the First Spermatogenic Wave in Wistar Rats. Anatomical record (Hoboken, N.J. : 2007) 5 31168949
2019 Molecular Cloning and Characterization of SYCP3 and TSEG2 Genes in the Testicles of Sexually Mature and Immature Yak. Genes 3 31671664
2025 Deciphering meiotic chromatin organization by SYCP3. Nucleic acids research 2 40488283
2020 The effects of Finasteride on the expression of Dazl, Tsga10, Sycp3, Prm2 genes during spermatogenesis in testes of NMRI mice. European review for medical and pharmacological sciences 1 32767344
2018 Cryo-electron tomography of SYCP3 fibers under native conditions. Methods in cell biology 1 29957214

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