Pathway Human Homo sapiens

PIWI-interacting RNA (piRNA) biogenesis

R-HSA-5601884 in Reactome release 97: under Gene Silencing by RNA, with 29 genes placed in it by the mapping files and 0 child pathways in the hierarchy.

The same number in the other species

Reactome writes the mouse and rat events it infers from a human pathway under the human number with the species token. A door opens only where that species' own list in this release holds the id; neither of the other two lists holds it. Whether the event was inferred from this one is what the record says.

The record
The genes
Parents and children

Scripts are off

This page reads the pathway's record from its source while you read the rest; with scripts off the card stays at its loading line. Reload with scripts on to see it, or open the source's own page from the link in the card.

01The record

Reactome's own record of this pathway

What this tells you

The pathway list, the hierarchy and the genes on this page are read from the files Reactome publishes for Reactome release 97, built into this site on 2026-09-09: the pathway list, the hierarchy relationship file and the two gene mapping files. The record card is the one live read, Reactome's own record of this pathway.

Reactome's download page describes the mapping files: Mapping files link the source database identifier to the lowest level pathway diagram or subset of the pathway, all levels of the pathway hierarchy or database identifier to all reactions. [R13] The gene list here is the all-levels mapping of NCBI Gene ids, filled from the all-levels mapping of Ensembl ids where the NCBI file has no row for a gene; each row names which file it came from by the shape of its source id. Each row carries the evidence codes the file writes for it, as written and unranked, and both where the file writes both; no page of Reactome's documentation the survey read defines the codes, so this page does not expand them. A gene id the identity files do not name is kept as the source's own id with no door rather than turned into a symbol.

On citing what a search finds, Reactome says: It should be remembered that while we strive to contain the most current and accurate data, Reactome should not be used in citations where other primary sources of information are available. [R12] The record card prints the literature Reactome attaches to a curated pathway for that reason. The data are public domain: All data in the Reactome database and files derived from that data are licensed under the Creative Commons Public Domain Dedication (CC0). User may copy, modify, and distribute these data, even for commercial purposes, without asking for permission. Attribution is encouraged but not required. [R10] The pathway illustrations are licensed apart, under CC BY 4.0, and none is shown here.

A gene on this list is one Reactome places in this pathway in this release, and that is all the row says: it does not say the gene is expressed in a tissue or associated with a disease, which are the other two explorers' questions, read from other sources. Reactome's papers of record are [R01] [R02].

[R01] Ragueneau E, Gong C, Sinquin P, Sevilla C, Beavers D, Grentner A, et al. (2026). The Reactome Knowledgebase 2026. Nucleic Acids Research 54:D673-D681. PMID 41251150, doi 10.1093/nar/gkaf1223.
[R02] Milacic M, Beavers D, Conley P, Gong C, Gillespie M, Griss J, et al. (2024). The Reactome Pathway Knowledgebase 2024. Nucleic Acids Research 52:D672-D678. PMID 37941124, doi 10.1093/nar/gkad1025.
[R10] Reactome, reactome.org. License Agreement. https://reactome.org/license, read 2026-09-09.
[R12] Reactome, reactome.org. Citing us. https://reactome.org/cite, read 2026-09-09.
[R13] Reactome, reactome.org. Download. https://reactome.org/download-data, read 2026-09-09.

Stable id: R-HSA-5601884.3
Class: Pathway
Species: Homo sapiens (human)
Inferred: no: a curated human pathway
Disease pathway: no
Released: 2014-12-11
Last updated: 2017-12-18
Events inside: 16, counted from the record

In germ cells of humans and mice, precursors of PIWI-interacting RNAs (piRNAs) are transcribed from a few hundred sequence clusters, as well as individual transposons, intergenic regions, and genes in the genome. These longer transcripts are processed to yield piRNAs of 26-30 nucleotides independently of DICER, the enzyme responsible for microRNAs (miRNAs) and small interfering RNAs (siRNAs) (reviewed in Girard and Hannon 2008, Siomi et al. 2011, Ishizu et al. 2012, Pillai and Chuma 2012, Bortvin 2013, Chuma and Nakano 2013, Sato and Siomi 2013). The initial step in processing long transcripts to piRNAs is cleavage by PLD6 (MitoPLD), which generates the mature 5' end. The cleavage products of PLD6 are bound by either PIWIL1 (HIWI, MIWI) or PIWIL2 (HILI, MILI) in complexes with several other proteins. The 3' end is trimmed by an unknown exonuclease to generate the mature piRNA. PIWIL1:piRNA complexes appear to be involved in post-transcriptional silencing in the cytosol while PIWIL2:piRNA complexes generate further piRNAs from transposon transcripts and other transcripts in the cytosol. Cleavage products from PIWIL2:piRNA may be loaded into either PIWIL2 or PIWIL4 (HIWI2, MIWI2). Loading into PIWIL2 forms a step in a cytosolic amplification loop called the "ping-pong cycle" which yields further PIWIL2:piRNA complexes from cleaved precursor RNAs. Loading into PIWIL4 yields a complex also containing TDRD9 that translocates to the nucleus and directs DNA methylation of cognate loci, causing transcriptional silencing during spermatogenesis. Transcriptional silencing by piRNAs is necessary to limit transposition of endogenous transposons such as L1 elements in the genome.

Literature Reactome attaches

Biology of PIWI-interacting RNAs: new insights into biogenesis and function inside and outside of germlinesGenes Dev., 2012, vol. 26, p. 2361-73PubMed 23124062
PIWI-interacting RNAs (piRNAs) - a mouse testis perspectiveBiochemistry Mosc., 2013, vol. 78, p. 592-602PubMed 23980886
piRNA and spermatogenesis in micePhilos. Trans. R. Soc. Lond., B, Biol. Sci., 2013, vol. 368, p. 20110338PubMed 23166399
Conserved themes in small-RNA-mediated transposon controlTrends Cell Biol., 2008, vol. 18, p. 136-48PubMed 18282709
PIWI-interacting small RNAs: the vanguard of genome defenceNat. Rev. Mol. Cell Biol., 2011, vol. 12, p. 246-58PubMed 21427766
piRNAs and their involvement in male germline development in miceDev. Growth Differ., 2012, vol. 54, p. 78-92PubMed 22221002
Piwi-interacting RNAs: biological functions and biogenesisEssays Biochem., 2013, vol. 54, p. 39-52PubMed 23829526

Reactome ContentService, this pathway's record · Reactome v97 · read 2026-10-01 ET · Reactome pathway browser"PIWI-interacting RNA (piRNA) biogenesis". Reactome, release 97, https://reactome.org/PathwayBrowser/#/R-HSA-5601884 with StableID: R-HSA-5601884.3 (accessed 2026-10-01 ET). Reactome version 97 (CC0).

Reading this pathway's record from Reactome (the pathway record).Still reading. A first read of a pathway can take a while; this page waits up to 35 seconds for it, and its scripts then bring in the panel, or a line saying what did not arrive.

02The genes

Genes Reactome places in this human pathway

The mapping files place 29 genes in this human pathway; showing 1 to 29, in pages of 100, sorted by symbol for reading. The order carries no ranking.

Genes Reactome places in this human pathway, page 1 of 1
Gene	Authority id	Mapping file id	Evidence codes
GeneASZ1	AuthorityHGNC:1350	Mapping file id136991 NCBI file	EvidenceIEA
GeneDDX4	AuthorityHGNC:18700	Mapping file id54514 NCBI file	EvidenceIEA
GeneFKBP6	AuthorityHGNC:3722	Mapping file id8468 NCBI file	EvidenceIEA
GeneHENMT1	AuthorityHGNC:26400	Mapping file id113802 NCBI file	EvidenceIEA
GeneHSP90AA1	AuthorityHGNC:5253	Mapping file id3320 NCBI file	EvidenceIEA
GeneMAEL	AuthorityHGNC:25929	Mapping file id84944 NCBI file	EvidenceIEA
GeneMOV10L1	AuthorityHGNC:7201	Mapping file id54456 NCBI file	EvidenceIEA
GeneMYBL1	AuthorityHGNC:7547	Mapping file id4603 NCBI file	EvidenceIEA
GenePIWIL1	AuthorityHGNC:9007	Mapping file id9271 NCBI file	EvidenceIEA
GenePIWIL2	AuthorityHGNC:17644	Mapping file id55124 NCBI file	EvidenceIEA
GenePIWIL4	AuthorityHGNC:18444	Mapping file id143689 NCBI file	EvidenceIEA
GenePLD6	AuthorityHGNC:30447	Mapping file id201164 NCBI file	EvidenceIEA
GenePOLR2A	AuthorityHGNC:9187	Mapping file id5430 NCBI file	EvidenceIEA
GenePOLR2B	AuthorityHGNC:9188	Mapping file id5431 NCBI file	EvidenceIEA
GenePOLR2C	AuthorityHGNC:9189	Mapping file id5432 NCBI file	EvidenceIEA
GenePOLR2D	AuthorityHGNC:9191	Mapping file id5433 NCBI file	EvidenceIEA
GenePOLR2E	AuthorityHGNC:9192	Mapping file id5434 NCBI file	EvidenceIEA
GenePOLR2F	AuthorityHGNC:9193	Mapping file id5435 NCBI file	EvidenceIEA
GenePOLR2G	AuthorityHGNC:9194	Mapping file id5436 NCBI file	EvidenceIEA
GenePOLR2H	AuthorityHGNC:9195	Mapping file id5437 NCBI file	EvidenceIEA
GenePOLR2I	AuthorityHGNC:9196	Mapping file id5438 NCBI file	EvidenceIEA
GenePOLR2J	AuthorityHGNC:9197	Mapping file id5439 NCBI file	EvidenceIEA
GenePOLR2K	AuthorityHGNC:9198	Mapping file id5440 NCBI file	EvidenceIEA
GenePOLR2L	AuthorityHGNC:9199	Mapping file id5441 NCBI file	EvidenceIEA
GeneTDRD1	AuthorityHGNC:11712	Mapping file id56165 NCBI file	EvidenceIEA
GeneTDRD12	AuthorityHGNC:25044	Mapping file id91646 NCBI file	EvidenceIEA
GeneTDRD6	AuthorityHGNC:21339	Mapping file id221400 NCBI file	EvidenceIEA
GeneTDRD9	AuthorityHGNC:20122	Mapping file id122402 NCBI file	EvidenceIEA
GeneTDRKH	AuthorityHGNC:11713	Mapping file id11022 NCBI file	EvidenceIEA

Evidence codes on this page: IEA, as the mapping file writes them; a row carrying two was written twice by the file, once under each. The mapping file id says which file placed the gene: an NCBI Gene id from NCBI2Reactome_All_Levels.txt, an Ensembl gene id from Ensembl2Reactome_All_Levels.txt. The two files can disagree about a code, so a row's codes are the one file's view. Measured by this site's build over this release on 2026-09-09: of the 138,908 human pathway-gene pairs both files place, 207 (0.149 per cent, over 47 genes) carry TAS in the Ensembl file where the NCBI rows carry IEA alone.

Reactome mapping files, the human rows for this pathway · Reactome release 97 · read 2026-09-09 · Reactome downloads"NCBI2Reactome_All_Levels.txt" and "Ensembl2Reactome_All_Levels.txt", Reactome, release 97, https://reactome.org/download-data/ (date of access 2026-09-09). Data CC0; attribution encouraged.

03The hierarchy

Parents and children in this release's hierarchy

Parents

Gene Silencing by RNAR-HSA-211000109 genes

Children

None: no pathway of this release's list names this one as a parent.

Reactome's hierarchy is a graph rather than a tree: a pathway can sit under more than one parent, and the gene counts are each pathway's own placements at every level under it, so a parent's count is not the sum of its children's.

Reactome, the human pathway list and hierarchy relationship file · Reactome release 97 · read 2026-09-09 · Reactome downloads"ReactomePathways.txt" and "ReactomePathwaysRelation.txt", Reactome, release 97, https://reactome.org/download-data/ (date of access 2026-09-09). Data CC0; attribution encouraged.