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HENMT1

Small RNA 2'-O-methyltransferase · UniProt Q5T8I9

Length
393 aa
Mass
44.5 kDa
Annotated
2026-06-10
20 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

HENMT1 is a small RNA 2'-O-methyltransferase that catalyzes 3'-terminal 2'-O-methylation of PIWI-interacting RNAs (piRNAs) during the final step of piRNA maturation, and this modification protects piRNAs from instability and length reduction (PMID:26496356, PMID:31996847). The methyl mark shields small RNAs from 3'→5' exonucleolytic degradation and non-templated tailing, a protective principle that extends beyond piRNAs: HENMT1 also methylates miRNAs, conferring resistance to the exoribonuclease PNPT1, increased Argonaute-2 affinity, and stronger target repression as shown for miR-21-5p and PDCD4 (PMID:32542340), and it methylates 3'-tRNA-derived fragments (3'-tRFs) to protect them from TUT4/TENT2 tailing (PMID:40463248). Through stabilization of these small RNAs, HENMT1 enforces transposable element silencing—repressing LINE-1 in germ cells and seminoma cells (PMID:26496356, PMID:28676534) and silencing endogenous retroviruses via 3'-tRFs in somatic contexts independent of piRNAs (PMID:40463248). HENMT1 is required for fertility in both sexes: loss causes spermiogenesis arrest at the elongating spermatid stage with transposon de-repression and germ cell death in males (PMID:26496356), and reduced follicle number with meiosis-II spindle defects in females (PMID:34590701). Homozygous loss-of-function variants in HENMT1 cause non-obstructive azoospermia in humans, with patient-matched mouse models recapitulating spermiogenesis arrest and LINE-1 de-repression (PMID:39318356, PMID:40645105).

Mechanistic history

Synthesis pass · year-by-year structured walk · 9 steps
  1. 2015 High

    Established HENMT1 as the enzyme required for 3'-terminal 2'-O-methylation of mammalian piRNAs and linked this modification to piRNA stability, transposon control, and male fertility.

    Evidence Mouse loss-of-function model with RNA-Seq and piRNA length/abundance and TE expression assays

    PMID:26496356

    Open questions at the time
    • Did not resolve catalytic residues or the biochemical mechanism
    • Did not establish the enzyme's direct biochemical activity in vitro
  2. 2017 Medium

    Demonstrated that HENMT1's transposon-repressing function is conserved in adult human testis, co-expressed with PIWIL1 and capable of suppressing LINE-1.

    Evidence Immunolocalization, laser-microdissection RT-PCR, RT-qPCR on testis biopsies, HENMT1-overexpressing TCam2 cells

    PMID:28676534

    Open questions at the time
    • Overexpression is gain-of-function rather than loss-of-function
    • Did not directly link HENMT1 methylation activity to the LINE-1 effect
  3. 2020 High

    Placed HENMT1 (Hen1 ortholog) at the final maturation step of piRNA biogenesis, acting after Zucchini cleavage and alongside Trimmer regardless of the endonucleolytic mechanism.

    Evidence Trimmer-knockout silkworm cell line and cell-free reconstitution of Zucchini-mediated cleavage

    PMID:31996847

    Open questions at the time
    • Pathway ordering established in insect system, not directly in mammals
    • Did not resolve how HENMT1 is recruited to mature pre-piRNAs
  4. 2020 High

    Extended HENMT1 substrate range to miRNAs, showing methylation confers exoribonuclease resistance, higher AGO2 affinity, and stronger translational repression.

    Evidence LC-MS/MS, PNPT1 digestion, AGO2 binding, and PDCD4 reporter assays for miR-21-5p in lung cancer cells

    PMID:32542340

    Open questions at the time
    • Demonstrated for a single miRNA; breadth of miRNA methylation unknown
    • Did not establish how substrate selection between piRNAs and miRNAs is governed
  5. 2021 High

    Showed HENMT1-mediated piRNA stabilization is also required for female fertility, affecting follicle number, oocyte transcriptome, and meiosis-II spindle integrity.

    Evidence Henmt1 mutant mouse, follicle counting, spindle imaging, oocyte transcriptome analysis

    PMID:34590701

    Open questions at the time
    • Mechanistic link between piRNA loss and spindle/microtubule defects not resolved
    • Specific destabilized small RNAs driving the oocyte phenotype not identified
  6. 2024 Low

    Proposed an atomic catalytic mechanism in which Mg2+ coordinated by conserved residues and terminal nucleotide hydroxyls enables 2'-OH deprotonation and methyl transfer from SAM.

    Evidence Computational modeling (MD, QM/MM) and evolutionary conservation analysis

    PMID:38198468

    Open questions at the time
    • Computational prediction with no experimental validation of His800/Asp859
    • No experimental structure of the HENMT1 active site reported
  7. 2024 High

    Established HENMT1 loss-of-function as directly causative of human male infertility by validating a patient nonsense variant in a matched mouse model.

    Evidence Whole-exome and Sanger sequencing, mouse model mimicking the patient variant, retrotransposon and TUNEL apoptosis assays

    PMID:39318356

    Open questions at the time
    • Single patient/variant; spectrum of pathogenic HENMT1 alleles unknown
    • No rescue experiment demonstrating reversibility
  8. 2025 Medium

    Extended HENMT1's transposon-silencing role to somatic cells via methylation of 3'-tRFs that silence ERVs, a piRNA-independent mechanism, and identified TUT4/TENT2 as the tailing enzymes counteracted.

    Evidence HENMT1 knockout cells, small RNA sequencing, massively parallel reporter assay, 2'-O-methylation detection, TUT4/TENT2 tailing assay (preprint)

    PMID:40463248

    Open questions at the time
    • Preprint, not yet peer-reviewed
    • Generality of 3'-tRF methylation across somatic tissues not established
  9. 2025 Medium

    Corroborated HENMT1's piRNA-stabilizing role in humans by linking a frameshift variant to azoospermia with reduced testicular piRNA abundance.

    Evidence Whole-exome and Sanger sequencing, small RNA sequencing of testicular tissue

    PMID:40645105

    Open questions at the time
    • Single patient with no functional rescue experiment
    • Causality inferred from genetics plus correlation, not directly demonstrated

Open questions

Synthesis pass · forward-looking unresolved questions
  • How HENMT1 selects among piRNA, miRNA, and 3'-tRF substrates and is recruited to each pathway, and experimental confirmation of its catalytic residues, remain unresolved.
  • No experimental structure or validated active-site mutagenesis
  • Substrate selectivity determinants between small RNA classes unknown
  • Recruitment mechanism to distinct biogenesis pathways uncharacterized

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0140098 catalytic activity, acting on RNA 4 GO:0003723 RNA binding 3 GO:0016740 transferase activity 3
Pathway
R-HSA-8953854 Metabolism of RNA 4 R-HSA-1474165 Reproduction 3
Partners

Evidence

Reading pass · 9 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2015 HENMT1 is required for 2'-O-methylation of the 3'-terminal nucleotide of mammalian piRNAs; loss of HENMT1 leads to piRNA instability, reduced piRNA bulk and length, transposable element de-repression in adult meiotic and haploid germ cells, and male sterility characterized by germ cell arrest at the elongating spermatid phase. Mouse loss-of-function model, RNA-Seq, RNA assays (piRNA length/abundance measurement, TE expression assays) PLoS genetics High 26496356
2021 HENMT1-mediated piRNA stabilization (via 3'-terminal 2'-O-methylation) is required for normal female fertility; Henmt1 mutant females show 3- to 4-fold reduction in follicle number, reduced litter sizes, meiosis-II spindle abnormalities, and a dramatically altered oocyte transcriptome including down-regulation of microtubule function transcripts. Henmt1 mutant mouse model, follicle counting, spindle imaging, transcriptome analysis Molecular human reproduction High 34590701
2020 HENMT1 is identified as the methyltransferase responsible for 3'-terminal 2'-O-methylation of mammalian miRNAs (demonstrated for miR-21-5p in lung cancer); methylated miR-21-5p shows increased resistance to 3'→5' exoribonuclease PNPT1 and higher affinity for Argonaute-2, resulting in greater stability and stronger translational repression of PDCD4. LC-MS/MS, qRT-PCR, northern blot with oxidation/β-elimination, PNPT1 digestion assay, Argonaute-2 binding assay, PDCD4 reporter assay Nucleic acids research High 32542340
2020 In the piRNA biogenesis pathway, Zucchini-dependent cleavage of pre-pre-piRNAs is accompanied by 2'-O-methylation by Hen1 (HENMT1 ortholog), and pre-piRNAs are matured by Trimmer and Hen1 regardless of the endonucleolytic mechanism (Zucchini-dependent or slicing-dependent), placing HENMT1 at the final maturation step of piRNA processing. Trimmer-knockout silkworm cell line, cell-free reconstitution system recapitulating Zucchini-mediated cleavage, biochemical fractionation Nature High 31996847
2017 HENMT1 and PIWIL1 are co-expressed in pachytene spermatocytes and spermatids in human testis; HENMT1-overexpressing TCam2 seminoma cells show lower LINE-1 transposon expression, supporting a conserved transposon-repressing function of HENMT1 in adult human testis. Immunolocalization, RT-PCR after laser microdissection, RT-qPCR on 222 testis biopsies, stable HENMT1-overexpressing cell line assay Reproduction (Cambridge, England) Medium 28676534
2024 Computational modeling of the HENMT1 catalytic mechanism indicates that Mg2+ is coordinated by four evolutionarily conserved residues plus the 3'-O and 2'-O of the terminal piRNA nucleotide; the reaction involves deprotonation of 2'-OH (potentially by His800 and Asp859) followed by methyl transfer from SAM to the 2'-O; Mg2+ is required for catalysis but not for substrate/cofactor binding. Computational modeling (molecular dynamics, quantum mechanics/molecular mechanics), evolutionary conservation analysis PloS one Low 38198468
2024 A homozygous nonsense variant in HENMT1 (c.555G>A, p.Trp185*) causes non-obstructive azoospermia in a human patient; mouse models carrying the equivalent variant display spermiogenesis arrest, significant LINE1 retrotransposon de-repression in testes, and increased spermatid apoptosis, establishing HENMT1 loss-of-function as directly causative of human male infertility. Whole-exome sequencing, Sanger sequencing, in vivo mouse model mimicking patient mutation, retrotransposon expression assay, TUNEL/apoptosis assay Andrology High 39318356
2025 HENMT1 methylates the 3'-ends of tRNA-derived small RNA fragments (3'-tRFs), protecting them from degradation and non-templated tailing by TUT4 and TENT2; 3'-tRFs with perfect complementarity to endogenous retroviral sequences silence ERV activity, and HENMT1 loss leads to reduced 3'-tRF stability and increased ERV activity, extending HENMT1's transposon-silencing role to somatic cells via a piRNA-independent mechanism. HENMT1 knockout cells, small RNA sequencing, massively parallel reporter assay (ERV target rules), 2'-O-methylation detection, TUT4/TENT2 tailing assay bioRxivpreprint Medium 40463248
2025 A homozygous frameshift variant in HENMT1 (c.47_75del, p.F16Sfs*3) was identified in a patient with non-obstructive azoospermia; testicular tissue from this patient showed reduced abundance of piRNAs, corroborating HENMT1's role in piRNA stabilization in humans. Whole-exome sequencing, Sanger sequencing, small RNA sequencing of testicular tissue Reproductive biomedicine online Medium 40645105

Source papers

Stage 0 corpus · 20 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2022 Whole-exome sequencing improves the diagnosis and care of men with non-obstructive azoospermia. American journal of human genetics 99 35172124
2015 HENMT1 and piRNA Stability Are Required for Adult Male Germ Cell Transposon Repression and to Define the Spermatogenic Program in the Mouse. PLoS genetics 99 26496356
2020 Integrative analyses of the RNA modification machinery reveal tissue- and cancer-specific signatures. Genome biology 73 32375858
2020 Zucchini consensus motifs determine the mechanism of pre-piRNA production. Nature 68 31996847
2020 3'-Terminal 2'-O-methylation of lung cancer miR-21-5p enhances its stability and association with Argonaute 2. Nucleic acids research 62 32542340
2018 Human-specific subcellular compartmentalization of P-element induced wimpy testis-like (PIWIL) granules during germ cell development and spermatogenesis. Human reproduction (Oxford, England) 41 29237021
2017 Expression patterns of HENMT1 and PIWIL1 in human testis: implications for transposon expression. Reproduction (Cambridge, England) 37 28676534
2015 Genome-wide site-specific differential methylation in the blood of individuals with Klinefelter syndrome. Molecular reproduction and development 23 25988574
2015 Identification of Novel Fusion Genes in Testicular Germ Cell Tumors. Cancer research 20 26659575
2017 Photoelectrochemical biosensor for HEN1 RNA methyltransferase detection using peroxidase mimics PtCu NFs and poly(U) polymerase-mediated RNA extension. Biosensors & bioelectronics 17 29277012
2024 DNA methylation correlates of chronological age in diverse human tissue types. Epigenetics & chromatin 16 39118140
2020 A Comprehensive Molecular and Clinical Analysis of the piRNA Pathway Genes in Ovarian Cancer. Cancers 8 33374923
2025 Novel homozygous variants in piRNA pathway factors lead to male infertility in humans. Reproductive biomedicine online 3 40645105
2021 HENMT1 is involved in the maintenance of normal female fertility in the mouse. Molecular human reproduction 3 34590701
2021 [PIWI/piRNA complex-mediated regulation of spermatogenesis]. Zhonghua nan ke xue = National journal of andrology 3 34914310
2025 HENMT1 restricts endogenous retrovirus activity by methylation of 3'-tRNA fragments. bioRxiv : the preprint server for biology 1 40463248
2024 Molecular basis of the reaction mechanism of the methyltransferase HENMT1. PloS one 1 38198468
2024 A homozygous nonsense variant in HENMT1 causes male infertility in humans and mice. Andrology 1 39318356
2023 Screening of potential key genes in esophageal cancer based on RBP and expression verification of HENMT1. Medicine 1 38065897
2022 The exploration of new biomarkers for oral cancer through the ceRNA network and immune microenvironment analysis. Medicine 1 36626444

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