One Loop to Rule Them All: The Ping-Pong Cycle and piRNA-Guided Silencing

Trends Biochem Sci. 2016 Apr;41(4):324-337. doi: 10.1016/j.tibs.2015.12.008. Epub 2016 Jan 19.


The PIWI-interacting RNA (piRNA) pathway is a conserved defense mechanism that protects the genetic information of animal germ cells from the deleterious effects of molecular parasites, such as transposons. Discovered nearly a decade ago, this small RNA silencing system comprises PIWI-clade Argonaute proteins and their associated RNA-binding partners, the piRNAs. In this review, we highlight recent work that has advanced our understanding of how piRNAs preserve genome integrity across generations. We discuss the mechanism of piRNA biogenesis, give an overview of common themes as well as differences in piRNA-mediated silencing between species, and end by highlighting known and emerging functions of piRNAs.

Keywords: PIWI proteins; piRNA biogenesis; ping-pong amplification loop; post-transcriptional gene silencing (PTGS); transcriptional gene silencing (TGS); transposon control.

Publication types

  • Review

MeSH terms

  • Animals
  • Argonaute Proteins / genetics*
  • Argonaute Proteins / metabolism
  • Chromosomal Proteins, Non-Histone / genetics
  • Chromosomal Proteins, Non-Histone / metabolism
  • Drosophila Proteins / genetics
  • Drosophila Proteins / metabolism
  • Drosophila melanogaster / genetics*
  • Drosophila melanogaster / metabolism
  • Gene Silencing*
  • Histones / genetics
  • Histones / metabolism
  • Humans
  • Microtubule-Associated Proteins / genetics
  • Microtubule-Associated Proteins / metabolism
  • RNA, Messenger / genetics*
  • RNA, Messenger / metabolism
  • RNA, Small Interfering / genetics*
  • RNA, Small Interfering / metabolism
  • RNA-Binding Proteins / genetics
  • RNA-Binding Proteins / metabolism
  • Transcription, Genetic


  • Argonaute Proteins
  • Chromosomal Proteins, Non-Histone
  • Cuff protein, Drosophila
  • Drosophila Proteins
  • Histones
  • Microtubule-Associated Proteins
  • RNA, Messenger
  • RNA, Small Interfering
  • RNA-Binding Proteins
  • del protein, Drosophila
  • rhi protein, Drosophila