Affinage

SMYD5

Protein-lysine N-trimethyltransferase SMYD5 · UniProt Q6GMV2

Length
418 aa
Mass
47.3 kDa
Annotated
2026-06-10
21 papers in source corpus 15 papers cited in narrative 16 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 7/7 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

SMYD5 is a SET- and MYND-domain lysine methyltransferase whose principal physiological substrate is the core ribosomal protein RPL40/eL40, which it trimethylates at lysine 22 to support mRNA translation (PMID:39048817, PMID:39103523). Substrate selection is governed by recognition of a KXY motif requiring a tyrosine at the +2 position, and active-site mutations abolish catalysis (PMID:40184250). Loss of SMYD5 eliminates RPL40 K22me3, reduces translation output, increases ribosome collisions indicative of disturbed elongation, and lowers polysome levels (PMID:39048817, PMID:39103523, PMID:40184250). SMYD5 and RPL40 K22me3 are upregulated in hepatocellular carcinoma (PMID:39103523). Beyond this ribosomal role, SMYD5 catalyzes H3K36me3 at promoter regions in a manner dependent on its C-terminal glutamic acid-rich domain and is recruited to chromatin by RNA polymerase II, distinct from SETD2-mediated H3K36me3 at gene bodies (PMID:35680905). SMYD5 also methylates non-histone proteins: it methylates PGC-1α to promote its ubiquitin-dependent degradation, attenuating mitochondrial biogenesis and respiration (PMID:35643234), and methylates the HIV-1 Tat protein while associating with the HIV-1 promoter and TAR RNA to activate viral transcription (PMID:36897778). In vitro reconstitution with recombinant SMYD5 shows no direct methylation of canonical histones, since these substrates lack the required +2 tyrosine, indicating that earlier-described H4K20me3-related heterochromatin functions in stem and cancer cells (PMID:28250819, PMID:28951459) reflect activities not explained by direct histone methylation (PMID:40184250). No experimentally determined structure of SMYD5 is available in this corpus.

Mechanistic history

Synthesis pass · year-by-year structured walk · 8 steps
  1. 2017 Medium

    Established the first proposed chromatin function of SMYD5, linking it to H4K20me3-marked heterochromatin maintenance, retroelement silencing, and stem cell self-renewal versus tumorigenesis.

    Evidence SMYD5 knockdown/depletion in mouse ES cells with ChIP-seq, histone mark Westerns, repeat element expression, cytogenetics, and xenograft assays

    PMID:28250819 PMID:28951459

    Open questions at the time
    • No direct in vitro demonstration that SMYD5 methylates H4K20
    • Effects could be indirect rather than via direct catalysis
    • Recruitment mechanism to heterochromatin undefined
  2. 2016 Medium

    Demonstrated an in vivo developmental role for Smyd5 in restraining myeloid hematopoiesis, the first organismal phenotype for the gene.

    Evidence Morpholino knockdown and CRISPR/Cas9 knockout in zebrafish with in situ hybridization and RT-PCR for hematopoietic markers

    PMID:27377701

    Open questions at the time
    • No biochemical substrate or molecular mechanism defined
    • Does not connect phenotype to a specific methylation event
  3. 2022 High

    Resolved SMYD5's chromatin enzymatic activity by assigning it promoter-localized H3K36me3 distinct from SETD2 gene-body marks and showing the C-terminal domain is required for activity.

    Evidence ChIP-seq, knockout rescue with full-length versus truncated constructs, and in vitro methyltransferase assay

    PMID:35680905

    Open questions at the time
    • Reconciliation with later negative histone methylation results unresolved
    • Mechanism of RNA Pol II-mediated recruitment not detailed
  4. 2022 Medium

    Extended SMYD5 to non-histone substrate methylation by showing it methylates PGC-1α to drive its degradation, coupling SMYD5 to mitochondrial function and intestinal inflammation.

    Evidence Co-IP, in vitro methylation with MS, cycloheximide chase, conditional KO mice, and Seahorse respirometry

    PMID:35643234

    Open questions at the time
    • Specific methylated lysines and their direct role in ubiquitination not fully mapped
    • Single lab
  5. 2023 Medium

    Identified a host-pathogen role in which SMYD5 binds the HIV-1 promoter, TAR RNA, and Tat, and methylates Tat to activate viral transcription.

    Evidence ChIP, RNA binding assay, in vitro methylation of Tat, and SMYD5 knockdown in cell lines and primary CD4+ T cells

    PMID:36897778

    Open questions at the time
    • Site and functional consequence of Tat methylation not fully resolved
    • Single lab
  6. 2024 High

    Redefined the principal physiological substrate of SMYD5 as ribosomal protein RPL40 K22, connecting the enzyme directly to translation elongation rather than chromatin.

    Evidence Biochemical-proteomics/MS substrate identification, in vitro methyltransferase assays, ribosome/polysome profiling, and SMYD5 ablation in cells and mouse models, replicated across independent labs

    PMID:39048817 PMID:39103523

    Open questions at the time
    • How RPL40 K22me3 mechanistically prevents ribosome collisions unresolved
    • Relationship between translation role and prior chromatin phenotypes unclear
  7. 2025 High

    Defined the substrate-recognition logic (KXY motif, +2 tyrosine) and experimentally rejected direct histone methylation, reframing earlier histone-mark phenotypes as likely indirect.

    Evidence In vitro methyltransferase assays with recombinant SMYD5 and synthetic peptides, active-site and motif mutagenesis, MS, and KO validation in K562 cells including negative histone results

    PMID:40184250

    Open questions at the time
    • Mechanistic basis of in-cell H3K36me3 ChIP signals not reconciled with in vitro negativity
    • Full census of KXY-bearing cellular substrates incomplete
  8. 2025 Low

    Expanded the disease-context substrate and interaction repertoire (FoxO1 methylation/degradation and metabolic-inflammatory signaling in synoviocytes; BRD4 interaction in hepatocellular carcinoma).

    Evidence Loss/gain-of-function in fibroblast-like synoviocytes with AAV KD in a CIA mouse model, and co-IP plus functional knockdown in LIHC cell lines

    PMID:40165083 PMID:40872497

    Open questions at the time
    • No explicit in vitro methylation assay reported for FoxO1
    • BRD4-SMYD5 functional axis not mechanistically characterized
    • Single-lab, correlative associations

Open questions

Synthesis pass · forward-looking unresolved questions
  • It remains unresolved how SMYD5's ribosomal RPL40 methylation activity mechanistically relates to the chromatin-associated H3K36me3 and heterochromatin phenotypes attributed to it, and whether the latter depend on its catalytic activity.
  • No experimental structure of SMYD5
  • No unifying model linking translation and chromatin functions
  • Direct catalytic basis of in-cell histone marks undefined

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0016740 transferase activity 6 GO:0140096 catalytic activity, acting on a protein 5 GO:0003723 RNA binding 1
Localization
GO:0005634 nucleus 3 GO:0005840 ribosome 3
Pathway
R-HSA-4839726 Chromatin organization 3 R-HSA-8953854 Metabolism of RNA 3 R-HSA-392499 Metabolism of proteins 1

Evidence

Reading pass · 16 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2022 SMYD5 is a histone methyltransferase that catalyzes H3K36me3 at promoter regions (distinct from SETD2-mediated H3K36me3 at gene bodies). SMYD5 is recruited to chromatin by RNA polymerase II, and its enzymatic activity depends on its C-terminal glutamic acid-rich domain; overexpression of full-length but not C-terminal domain-truncated Smyd5 restores H3K36me3 at promoters in knockout cells. ChIP-seq, Smyd5 knockout rescue with full-length vs. truncated constructs, in vitro methyltransferase assay Nature communications High 35680905
2024 SMYD5 trimethylates the core ribosomal protein RPL40 (ubiquitin fusion protein partner) at lysine 22 (rpL40K22me3). This modification regulates mRNA translation output; loss of SMYD5 leads to reduced translation output and increased ribosome collisions indicative of disturbed elongation. Identified by a biochemical-proteomics strategy as the principal physiological substrate of SMYD5. Biochemical-proteomics (mass spectrometry), in vitro methyltransferase assay, ribosome profiling/polysome analysis, SMYD5 ablation in cell lines and mouse models Nature High 39048817
2024 SMYD5 has robust in vitro methyltransferase activity toward RPL40 K22 and primarily catalyzes RPL40 K22me3 in cells. Loss of SMYD5 and RPL40 K22me3 reduces translation output and causes increased ribosome collisions. SMYD5 and RPL40 K22me3 are upregulated in hepatocellular carcinoma. In vitro methyltransferase assay with recombinant SMYD5, SMYD5 knockout cell lines, ribosome fractionation/polysome profiling, genetically engineered mouse models and PDX models Cell research High 39103523
2025 SMYD5 trimethylates RPL40/eL40 at lysine 22 through recognition of a KXY motif (tyrosine at the +2 position is required). Active site mutations abolish this activity. SMYD5 does not methylate histones in vitro, and its requirement for the KXY motif explains this lack of activity toward canonical histone substrates. SMYD5 KO in K562 cells causes complete loss of RPL40 K22 methylation and decreased polysome levels. In vitro methyltransferase assay with recombinant SMYD5 and synthetic peptides, active-site mutagenesis, SMYD5 KO in K562 cells, mass spectrometry, systematic recognition motif analysis Cell reports High 40184250
2025 SMYD5 does not methylate histones in vitro (negative finding). Systematic analysis of its recognition motif shows SMYD5 requires a KXY motif, and the absence of a tyrosine at +2 in canonical histone substrates explains its lack of histone methyltransferase activity. In vitro methyltransferase assay with recombinant SMYD5 toward histone substrates, systematic peptide motif analysis Cell reports High 40184250
2017 SMYD5 mediates H4K20me3 at heterochromatin regions in embryonic stem cells. Depletion of SMYD5 leads to global decreases in H4K20me3 levels, redistribution of heterochromatin constituents (H3K9me3/2, G9a, HP1α), and de-repression of endogenous retroelements (LTR, LINE elements). Loss of SMYD5-dependent heterochromatin silencing near genic regions upregulates lineage-specific genes, compromising ES cell self-renewal. ChIP-seq, SMYD5 knockdown in mouse ES cells, Western blot for histone marks, repeat element expression analysis Epigenetics & chromatin Medium 28250819
2017 SMYD5 depletion during ES cell differentiation causes genome-wide decreases in H4K20me3 and H3K9me3, derepression of LTR and LINE repetitive elements, chromosomal aberrations, and formation of transformed cells with a cancer-like expression signature. Depletion of SMYD5 in human colon and lung cancer cells increases tumor growth. SMYD5 depletion in mouse ES cells during differentiation, ChIP-seq, cytogenetics/karyotyping, xenograft tumor assays Cancer research Medium 28951459
2022 SMYD5 interacts with PGC-1α (co-immunoprecipitation) and mediates lysine methylation of PGC-1α, subsequently facilitating its ubiquitination and degradation. This post-translational mechanism attenuates mitochondrial biogenesis, respiration, and function in intestinal epithelial cells. Smyd5 conditional knockout in IECs protects mice from DSS-induced colitis. Co-immunoprecipitation, in vitro methylation assay with mass spectrometry identification of methylated lysines, cycloheximide chase assay, Smyd5 conditional KO mice with colitis model, Seahorse respirometry Cellular and molecular gastroenterology and hepatology Medium 35643234
2023 SMYD5 associates in vivo with the HIV-1 promoter, binds the HIV-1 TAR element RNA and Tat protein, and methylates Tat in vitro. SMYD5 activates the HIV-1 promoter with or without Tat; knockdown of SMYD5 decreases HIV-1 transcription in cell lines and primary CD4+ T cells. Tat expression increases SMYD5 protein levels in a manner dependent on the Tat cofactor USP11. ChIP assay (in vivo promoter association), RNA binding assay (TAR element), in vitro methylation assay (Tat substrate), SMYD5 knockdown in cell lines and primary T cells, HIV-1 transcription reporter assays Cell reports Medium 36897778
2024 SMYD5 represses the key mild hypothermia response (MHR) gene SP1 at euthermia; this repression correlates with temperature-dependent levels of H3K36me3 at the SP1 locus and globally, identified through a forward CRISPR-Cas9 mutagenesis screen. Forward CRISPR-Cas9 mutagenesis screen, ChIP analysis for H3K36me3, transcriptional reporter/gene expression assays Cell reports Medium 39083378
2016 Loss of Smyd5 in zebrafish (morpholino knockdown and CRISPR/Cas9 knockout) leads to increased expression of primitive and definitive hematopoietic markers (pu.1, mpx, l-plastin, cmyb), establishing a role for Smyd5 in restraining myeloid hematopoiesis during embryogenesis. Morpholino knockdown, CRISPR/Cas9 knockout in zebrafish embryos, in situ hybridization and RT-PCR for hematopoietic markers Scientific reports Medium 27377701
2022 AlphaFold structural modeling of SMYD5 reveals an incomplete target lysine access channel lacking the evolutionarily conserved tri-aromatic arrangement, which correlates with low H3/H4 histone catalytic activity. SMYD5 contains a C-terminal poly-glutamic acid tract and a 30-residue MYND domain insertion that regulate structural stability, and a predicted N-terminal mitochondrial targeting signal containing a non-classical nuclear localization signal. AlphaFold structural prediction validated by comparison to known SMYD crystal structures using inter-residue distance maps; thermal stability assays Biomolecules Low 35740908
2021 Protamine (a histone substitute in chromatin condensation during spermatogenesis) enhances SMYD5 thermal stability and physically interacts with SMYD5. The interaction is independent of the poly-E tract and MYND domain insertion. The C-terminal poly-glutamic acid tract and MYND domain M-insertion also regulate SMYD5 structural stability. Protamine has opposite (destabilizing) effects on the closely related SMYD2. Thermal stability assay (DSF), machine learning-assisted screening (Silver Bullets Bio library), co-precipitation/binding assays for protamine-SMYD5 interaction Biochemical and biophysical research communications Low 33676231
2024 SMYD5 knockdown in lung cancer cell lines reduces H4K20 trimethylation at the SH2B3 locus, leading to increased SH2B3 expression and inhibition of cell migration and invasion via changes in epithelial-mesenchymal transition markers and MMP9 expression. SMYD5 knockdown in NCI-H1299 and H1703 cell lines, ChIP for H4K20me3, migration/invasion assays, EMT marker analysis Molecules and cells Low 38723947
2025 SMYD5 mediates methylation of FoxO1 in fibroblast-like synoviocytes, which accelerates FoxO1 degradation through ubiquitination, promoting FLS proliferation. Additionally, SMYD5 promotes upregulation of hexokinase-2 (HK2), increasing lactate release and activating NF-κB signaling to intensify inflammation in FLS. Loss-of-function and gain-of-function experiments in FLS, co-immunoprecipitation (inferred from context), AAV-mediated KD in CIA mouse model, downstream pathway analysis Cellular & molecular biology letters Low 40165083
2025 SMYD5 physically interacts with BRD4 in hepatocellular carcinoma cells; this interaction is identified as a potential therapeutic axis. Knockdown of SMYD5 inhibits cell proliferation and increases apoptosis in LIHC cell lines. Co-immunoprecipitation (interaction), functional knockdown assays, bioinformatics/in silico docking Pharmaceuticals (Basel, Switzerland) Low 40872497

Source papers

Stage 0 corpus · 21 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2007 The response regulator RRG-1 functions upstream of a mitogen-activated protein kinase pathway impacting asexual development, female fertility, osmotic stress, and fungicide resistance in Neurospora crassa. Molecular biology of the cell 80 17392518
2017 SMYD5 regulates H4K20me3-marked heterochromatin to safeguard ES cell self-renewal and prevent spurious differentiation. Epigenetics & chromatin 55 28250819
2022 SMYD5 catalyzes histone H3 lysine 36 trimethylation at promoters. Nature communications 38 35680905
2024 SMYD5 methylation of rpL40 links ribosomal output to gastric cancer. Nature 35 39048817
2017 SMYD5 Controls Heterochromatin and Chromosome Integrity during Embryonic Stem Cell Differentiation. Cancer research 30 28951459
2016 Smyd5 plays pivotal roles in both primitive and definitive hematopoiesis during zebrafish embryogenesis. Scientific reports 29 27377701
2022 Epithelial SMYD5 Exaggerates IBD by Down-regulating Mitochondrial Functions via Post-Translational Control of PGC-1α Stability. Cellular and molecular gastroenterology and hepatology 17 35643234
2023 The lysine methyltransferase SMYD5 amplifies HIV-1 transcription and is post-transcriptionally upregulated by Tat and USP11. Cell reports 15 36897778
2024 SMYD5 is a ribosomal methyltransferase that catalyzes RPL40 lysine methylation to enhance translation output and promote hepatocellular carcinoma. Cell research 13 39103523
2022 Unique SMYD5 Structure Revealed by AlphaFold Correlates with Its Functional Divergence. Biomolecules 11 35740908
2022 SMYD5 acts as a potential biomarker for hepatocellular carcinoma. Experimental cell research 9 35218722
2002 Glucose-inducible expression of rrg1+ in Schizosaccharomyces pombe: post-transcriptional regulation of mRNA stability mediated by the downstream region of the poly(A) site. Nucleic acids research 6 11861905
2024 Negative regulation of SH2B3 by SMYD5 controls epithelial-mesenchymal transition in lung cancer. Molecules and cells 5 38723947
2021 Sperm chromatin-condensing protamine enhances SMYD5 thermal stability. Biochemical and biophysical research communications 5 33676231
2024 SMYD5 is a regulator of the mild hypothermia response. Cell reports 3 39083378
2025 Novel regulation mechanism of histone methyltransferase SMYD5 in rheumatoid arthritis. Cellular & molecular biology letters 1 40165083
2023 A flow cytometry-based assay to investigate HIV-1 expression in SMYD5 shRNA containing primary CD4+ T cells. STAR protocols 1 37925635
2025 SMYD5 is a ribosomal methyltransferase that trimethylates RPL40 lysine 22 through recognition of a KXY motif. Cell reports 0 40184250
2025 SMYD5-BRD4 Interaction Drives Hepatocellular Carcinoma Progression: A Combined in Silico and Experimental Analysis. Pharmaceuticals (Basel, Switzerland) 0 40872497
2024 SMYD5 is a regulator of the mild hypothermia response. bioRxiv : the preprint server for biology 0 37333301
2002 A glucose-inducible gene in Schizosaccharomyces pombe, rrg1+, is involved in negative regulation of G2/M progression. Molecules and cells 0 12442907

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