Affinage

BYSL

Bystin · UniProt Q13895

Round 2 corrected
Length
437 aa
Mass
49.6 kDa
Annotated
2026-04-28
46 papers in source corpus 8 papers cited in narrative 8 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

BYSL (bystin) is a conserved nucleolar protein essential for early pre-rRNA processing and 40S ribosomal subunit biogenesis, with critical roles in preimplantation embryonic development and cell proliferation. The yeast ortholog Enp1 associates with Nop1, U3 and U14 snoRNAs to mediate cleavage at sites A0, A1, and A2 in pre-rRNA, generating 18S rRNA (PMID:12527778); mammalian BYSL localizes to the nucleolus and is required for 40S subunit formation, trophectoderm differentiation, and blastocyst formation, with Bysl-null mouse embryos dying shortly after implantation (PMID:17055491, PMID:17242206). In cancer cells, BYSL forms a complex with RIOK2 and mTOR to activate AKT/mTOR signaling and promotes epithelial–mesenchymal transition through GSK-3β/β-catenin signaling; its transcription is directly driven by c-MYC (PMID:33628587, PMID:33178594, PMID:41854887). BYSL expression is post-transcriptionally suppressed by miR-378a-3p, which targets its 3′-UTR (PMID:35154253).

Mechanistic history

Synthesis pass · year-by-year structured walk · 8 steps
  1. 1997 Medium

    Identification of the yeast ortholog ENP1 as an essential nuclear protein established that the BYSL/Enp1 family resides in the nucleus, setting the stage for determining its molecular function.

    Evidence Immunohistochemistry of c-myc-tagged ENP1 fusion protein in S. cerevisiae

    PMID:9034325

    Open questions at the time
    • Single epitope-tag method; endogenous localization not confirmed
    • Molecular function and nuclear sub-compartment unresolved
    • No mammalian data at this point
  2. 2003 High

    Functional analysis of a temperature-sensitive enp1 mutant revealed that Enp1 is required for early pre-rRNA processing (A0, A1, A2 cleavages) and 40S ribosomal subunit production, defining the core molecular role of the BYSL family in ribosome biogenesis.

    Evidence Northern analysis, pulse-chase of rRNA precursors, and co-precipitation with Nop1, U3 and U14 snoRNAs in yeast enp1-1 mutant

    PMID:12527778

    Open questions at the time
    • Whether the mammalian ortholog has the same ribosome biogenesis function was untested
    • Direct RNA-binding activity of Enp1 not demonstrated
    • Position within the 90S/SSU processome unclear
  3. 2006 High

    Knockout of mouse Bysl established the gene as essential for early embryo survival post-implantation and demonstrated direct binding to the adhesion molecule trophinin, connecting ribosome biogenesis factor function to developmental biology.

    Evidence Targeted gene disruption in mouse; binding assay for trophinin interaction

    PMID:17055491

    Open questions at the time
    • Whether embryonic lethality results from ribosome biogenesis failure or trophinin-related adhesion defects was unresolved
    • Mechanism of trophinin interaction and its physiological relevance unclear
  4. 2007 High

    Sub-nucleolar localization and direct requirement for 40S subunit production were confirmed in mammalian cells, and BYSL loss was shown to block blastocyst formation by preventing trophectoderm differentiation, unifying the ribosome biogenesis and embryonic lethality phenotypes.

    Evidence siRNA and dominant-negative mutants in preimplantation embryos; fluorescent live imaging; ribosomal subunit fractionation; shRNA in ES cells

    PMID:17242206

    Open questions at the time
    • Whether trophectoderm failure is a direct or indirect consequence of ribosome biogenesis deficiency not fully resolved
    • Mammalian pre-rRNA processing intermediates affected by BYSL loss not mapped at nucleotide resolution
  5. 2020 Medium

    Beyond ribosome biogenesis, BYSL was found to promote EMT in glioblastoma through GSK-3β phosphorylation and nuclear β-catenin accumulation, revealing a gain-of-function oncogenic signaling axis.

    Evidence Knockdown and overexpression in GBM cell lines; Western blot for EMT markers; pharmacological GSK-3β inhibitor rescue

    PMID:33178594

    Open questions at the time
    • Whether GSK-3β regulation is direct or secondary to ribosome/translation changes unknown
    • Single-lab observation without independent replication
    • In vivo EMT phenotype not demonstrated
  6. 2021 Medium

    Discovery that BYSL forms a complex with RIOK2 and mTOR provided a mechanistic bridge between its ribosome biogenesis role and AKT/mTOR signaling activation in glioma, with in vivo tumor growth effects.

    Evidence Reciprocal co-immunoprecipitation; double immunofluorescence; orthotopic xenograft model

    PMID:33628587

    Open questions at the time
    • Stoichiometry and directness of the BYSL–RIOK2–mTOR complex not defined biochemically
    • Whether the complex functions in non-cancer contexts unknown
    • Relationship between 40S biogenesis role and mTOR complex formation unexplored
  7. 2022 Medium

    Identification of miR-378a-3p as a direct post-transcriptional suppressor of BYSL via 3′-UTR binding established an upstream regulatory mechanism and linked BYSL to hypoxia-responsive invasion in osteosarcoma.

    Evidence Dual-luciferase reporter assay; rescue experiments; invasion assays under hypoxia

    PMID:35154253

    Open questions at the time
    • Single-lab finding; other miRNAs targeting BYSL not surveyed
    • Nrf2 induction by BYSL under hypoxia mechanistically unexplained
  8. 2026 Medium

    c-MYC was identified as a direct transcriptional activator of BYSL, and BYSL knockdown in AML cells caused G0/G1 arrest and reduced PI3K/AKT phosphorylation, extending the oncogenic circuit to hematologic malignancies.

    Evidence ChIP-qPCR confirming c-MYC at BYSL promoter; siRNA knockdown in AML cell lines; Western blot for PI3K/AKT

    PMID:41854887

    Open questions at the time
    • Single-lab study; c-MYC regulation not confirmed genome-wide or in non-AML contexts
    • Whether PI3K/AKT reduction is mediated through mTOR complex or ribosome biogenesis deficiency not distinguished

Open questions

Synthesis pass · forward-looking unresolved questions
  • A central unresolved question is whether the oncogenic signaling activities of BYSL (AKT/mTOR, GSK-3β/β-catenin) are mechanistically separable from its essential nucleolar role in 40S ribosome biogenesis, or whether they represent downstream consequences of altered translational capacity.
  • No separation-of-function mutants exist to distinguish ribosome biogenesis from signaling roles
  • Structural basis of BYSL interactions with pre-rRNA, RIOK2, and mTOR undefined
  • Physiological relevance of trophinin binding in adult tissues remains unclear

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0003723 RNA binding 1
Localization
GO:0005634 nucleus 2 GO:0005730 nucleolus 1
Pathway
R-HSA-162582 Signal Transduction 3 GO:0005840 ribosome 2 R-HSA-392499 Metabolism of proteins 2 R-HSA-1640170 Cell Cycle 1
Partners
MTORMYCNOP1RIOK2
Complex memberships
BYSL-RIOK2-mTOR complex

Evidence

Reading pass · 8 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1997 The yeast ortholog ENP1 encodes an essential nuclear protein of 483 amino acids that localizes to the nucleus, establishing nuclear localization as a conserved property of the BYSL/Enp1 protein family. Immunohistochemistry using c-myc epitope-tagged fusion protein expressed in yeast Gene Medium 9034325
2003 Yeast Enp1 is required for early pre-rRNA processing at sites A0, A1, and A2, and is essential for synthesis of 20S pre-rRNA and 18S rRNA, thereby enabling 40S ribosomal subunit biogenesis. Enp1 physically associates with Nop1 protein and with U3 and U14 snoRNAs. Northern analysis of rRNA precursors in temperature-sensitive enp1-1 mutant; pulse-chase analysis; co-precipitation assay Nucleic acids research High 12527778
2006 Human bystin (BYSL gene product) is a cytoplasmic protein that directly binds to trophinin, a cell adhesion molecule involved in embryo implantation. Targeted disruption of the mouse Bysl gene results in embryonic lethality shortly after implantation, demonstrating that bystin is essential for early mouse embryo survival. Targeted gene disruption (knockout mouse); binding assay demonstrating direct trophinin interaction FEBS letters High 17055491
2007 Mammalian Bysl localizes to the nucleolus (with diffuse nucleoplasmic distribution) and is required for 40S ribosomal subunit biogenesis. Loss of Bysl function via siRNA or dominant-negative mutants causes defects in 40S subunit formation and arrests embryonic development just prior to blastocyst formation, blocking trophectoderm differentiation. Bysl silencing also inhibits embryonic stem cell proliferation. siRNA knockdown in preimplantation embryos; dominant-negative mutants; fluorescent protein fusion live-cell imaging; ribosomal subunit analysis; episomal shRNA knockdown in ES cells Molecular and cellular biology High 17242206
2020 BYSL promotes glioblastoma cell migration, invasion, and epithelial-mesenchymal transition (EMT) through the GSK-3β/β-catenin signaling pathway. Overexpression of BYSL increases phosphorylation of GSK-3β and nuclear distribution of β-catenin, upregulating mesenchymal markers (β-catenin, N-cadherin) and downregulating E-cadherin. Inhibition of GSK-3β partially reverses BYSL-mediated EMT effects. Knockdown and overexpression in GBM cell lines; Western blot for EMT markers and signaling molecules; pharmacological GSK-3β inhibition rescue experiment; immunohistochemistry Frontiers in oncology Medium 33178594
2021 BYSL forms a complex with RIOK2 and mTOR in glioma cells. BYSL co-localizes with RIOK2, and overexpression of BYSL or RIOK2 increases AKT/mTOR signaling activity, while silencing either decreases AKT/mTOR activity and inhibits tumor growth in vivo. Co-immunoprecipitation; double immunofluorescence co-localization; Western blot for AKT/mTOR pathway activity; orthotopic xenograft mouse model Cancer biology & medicine Medium 33628587
2022 BYSL expression is post-transcriptionally regulated by miR-378a-3p, which binds to the 3'-UTR of BYSL mRNA and suppresses its expression. Under hypoxia, miR-378a-3p suppresses osteosarcoma cell invasion and inhibits EMT by repressing BYSL; upregulation of BYSL enhances Nrf2 expression under hypoxia. Dual-luciferase reporter assay confirming miR-378a-3p binding to BYSL 3'-UTR; rescue assay; functional invasion assays under hypoxia/normoxia Frontiers in genetics Medium 35154253
2026 BYSL knockdown in AML cell lines inhibits cell proliferation, reduces colony-forming ability, and induces G0/G1 cell cycle arrest. Mechanistically, BYSL suppression decreases PI3K and AKT phosphorylation. BYSL transcription is directly regulated by c-MYC binding to its promoter, as confirmed by ChIP-qPCR. siRNA knockdown in AML cell lines; Western blot for PI3K/AKT phosphorylation; ChIP-qPCR confirming c-MYC binding to BYSL promoter; proliferation and colony-forming assays Clinical and experimental medicine Medium 41854887

Source papers

Stage 0 corpus · 46 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2006 Global, in vivo, and site-specific phosphorylation dynamics in signaling networks. Cell 2861 17081983
2005 Towards a proteome-scale map of the human protein-protein interaction network. Nature 2090 16189514
2012 Insights into RNA biology from an atlas of mammalian mRNA-binding proteins. Cell 1718 22658674
2002 Generation and initial analysis of more than 15,000 full-length human and mouse cDNA sequences. Proceedings of the National Academy of Sciences of the United States of America 1479 12477932
2015 The BioPlex Network: A Systematic Exploration of the Human Interactome. Cell 1118 26186194
2017 Architecture of the human interactome defines protein communities and disease networks. Nature 1085 28514442
2015 A human interactome in three quantitative dimensions organized by stoichiometries and abundances. Cell 1015 26496610
2014 A proteome-scale map of the human interactome network. Cell 977 25416956
2020 A reference map of the human binary protein interactome. Nature 849 32296183
2003 Complete sequencing and characterization of 21,243 full-length human cDNAs. Nature genetics 754 14702039
2021 Dual proteome-scale networks reveal cell-specific remodeling of the human interactome. Cell 705 33961781
2012 A census of human soluble protein complexes. Cell 689 22939629
2011 Phylogenetic-based propagation of functional annotations within the Gene Ontology consortium. Briefings in bioinformatics 656 21873635
2006 A protein-protein interaction network for human inherited ataxias and disorders of Purkinje cell degeneration. Cell 610 16713569
2018 High-Density Proximity Mapping Reveals the Subcellular Organization of mRNA-Associated Granules and Bodies. Molecular cell 580 29395067
2014 Parent-of-origin-specific allelic associations among 106 genomic loci for age at menarche. Nature 445 25231870
2004 The status, quality, and expansion of the NIH full-length cDNA project: the Mammalian Gene Collection (MGC). Genome research 438 15489334
2022 OpenCell: Endogenous tagging for the cartography of human cellular organization. Science (New York, N.Y.) 432 35271311
2009 A genome-wide meta-analysis identifies 22 loci associated with eight hematological parameters in the HaemGen consortium. Nature genetics 423 19820697
2015 Panorama of ancient metazoan macromolecular complexes. Nature 407 26344197
2010 Genome-wide association study of hematological and biochemical traits in a Japanese population. Nature genetics 406 20139978
2021 A proximity-dependent biotinylation map of a human cell. Nature 339 34079125
2012 Interpreting cancer genomes using systematic host network perturbations by tumour virus proteins. Nature 319 22810586
2010 Dynamics of cullin-RING ubiquitin ligase network revealed by systematic quantitative proteomics. Cell 318 21145461
2009 Multiple loci influence erythrocyte phenotypes in the CHARGE Consortium. Nature genetics 294 19862010
2012 A high-throughput approach for measuring temporal changes in the interactome. Nature methods 273 22863883
2017 Optimized fragmentation schemes and data analysis strategies for proteome-wide cross-link identification. Nature communications 221 28524877
2009 Proteomic analysis of integrin-associated complexes identifies RCC2 as a dual regulator of Rac1 and Arf6. Science signaling 207 19738201
2018 An AP-MS- and BioID-compatible MAC-tag enables comprehensive mapping of protein interactions and subcellular localizations. Nature communications 201 29568061
2011 Next-generation sequencing to generate interactome datasets. Nature methods 200 21516116
2007 EnP1, a microsporidian spore wall protein that enables spores to adhere to and infect host cells in vitro. Eukaryotic cell 80 17557882
2005 EnP1 and EnP2, two proteins associated with the Encephalitozoon cuniculi endospore, the chitin-rich inner layer of the microsporidian spore wall. International journal for parasitology 54 16368098
2003 Enp1, a yeast protein associated with U3 and U14 snoRNAs, is required for pre-rRNA processing and 40S subunit synthesis. Nucleic acids research 53 12527778
2005 Identification of CCND3 and BYSL as candidate targets for the 6p21 amplification in diffuse large B-cell lymphoma. Clinical cancer research : an official journal of the American Association for Cancer Research 36 16322284
2007 Crucial role of Bysl in mammalian preimplantation development as an integral factor for 40S ribosome biogenesis. Molecular and cellular biology 28 17242206
2021 BYSL contributes to tumor growth by cooperating with the mTORC2 complex in gliomas. Cancer biology & medicine 25 33628587
2020 BYSL Promotes Glioblastoma Cell Migration, Invasion, and Mesenchymal Transition Through the GSK-3β/β-Catenin Signaling Pathway. Frontiers in oncology 25 33178594
1997 ENP1, an essential gene encoding a nuclear protein that is highly conserved from yeast to humans. Gene 24 9034325
2006 The Bysl gene product, bystin, is essential for survival of mouse embryos. FEBS letters 12 17055491
2021 DDX10 and BYSL as the potential targets of chondrosarcoma and glioma. Medicine 9 34797290
2022 Hypoxia-Induced miR-378a-3p Inhibits Osteosarcoma Invasion and Epithelial-to-Mesenchymal Transition via BYSL Regulation. Frontiers in genetics 8 35154253
2024 Microsporidian EnP1 alters host cell H2B monoubiquitination and prevents ferroptosis facilitating microsporidia survival. Proceedings of the National Academy of Sciences of the United States of America 7 39141344
2018 Bystin (BYSL) as a possible marker of severe hypoxic-ischemic changes in neuropathological examination of forensic cases. Forensic science, medicine, and pathology 6 29349722
2023 Sarcomatoid renal cell tumor harboring a novel BYSL::TFEB fusion with concurrent TFEB amplification. Genes, chromosomes & cancer 3 36704911
2026 EnP1 exploits H2Aub-dependent epigenetic reprogramming to promote microsporidia proliferation in host cells. PLoS pathogens 0 41499632
2026 Investigation of the expression and potential mechanistic role of BYSL in acute myeloid leukemia. Clinical and experimental medicine 0 41854887