title: Is RNA-dependent RNA polymerase essential for transposon control?
abstract: BACKGROUND
  Eukaryotes use RNA interference and RNA-based epigenetic regulation to control transposon activity. In the standard pathways of RNA-based transcriptional and post-transcriptional silencing the protein complex RNA-dependent RNA polymerase (RdRP) plays a crucial role. However, alternative pathways that bypass RdRP have recently been described. Hence two important questions are: is RdRP truly a necessary component for transposon control, and are the alternative RNA-based strategies also capable of controlling transposable elements?
  
  
  RESULTS
  We have studied the interplay between host RNAi pathways and transposons using mathematical models. We show that the canonical RdRP-based model controls transposons tightly, mainly via the feedback of cytoplasmic small RNA amplification. Next, we consider two variants lacking RdRP and instead employing antisense transcription of transposons. We show that transposon activity is also controlled by the alternative pathways, although cytoplasmic small RNA amplification is absent. Instead, control occurs in the nucleus, through a feedback in the epigenetic regulation.
  
  
  CONCLUSIONS
  Concluding, our models show that the control of transposon activity can be achieved by alternative pathways that lack RdRP and act through different feedback mechanisms. Thus, although RdRP activity is ubiquitous in eukaryotes, it need not be a general requirement for transposon control.
authors.affiliation: Theoretical Biology and Bioinformatics Group, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands. anton.crombach@crg.es
authors.forename: Anton
authors.initials: A
authors.lastname: Crombach
authors.forename: Paulien
authors.initials: P
authors.lastname: Hogeweg
mesh_terms: D002843:Chromatin / Q000502:physiology; D004251:DNA Transposable Elements / Q000502:physiology*; D044127:Epigenesis, Genetic / Q000502:physiology*; D008954:Models, Biological; D034622:RNA Interference / Q000502:physiology*; D012324:RNA-Dependent RNA Polymerase / Q000378:metabolism / Q000502:physiology*
chemical_list: D002843:Chromatin; D004251:DNA Transposable Elements; D012324:RNA-Dependent RNA Polymerase