Maelstrom Represses Canonical Polymerase II Transcription within Bi-directional piRNA Clusters in Drosophila melanogaster

Timothy H. Chang, Eugenio Mattei, Ildar Gainetdinov, Cansu Colpan, Zhiping Weng, Phillip D. Zamore

Research output: Contribution to journalArticlepeer-review

Abstract

In Drosophila, 23–30 nt long PIWI-interacting RNAs (piRNAs) direct the protein Piwi to silence germline transposon transcription. Most germline piRNAs derive from dual-strand piRNA clusters, heterochromatic transposon graveyards that are transcribed from both genomic strands. These piRNA sources are marked by the heterochromatin protein 1 homolog Rhino (Rhi), which facilitates their promoter-independent transcription, suppresses splicing, and inhibits transcriptional termination. Here, we report that the protein Maelstrom (Mael) represses canonical, promoter-dependent transcription in dual-strand clusters, allowing Rhi to initiate piRNA precursor transcription. Mael also represses promoter-dependent transcription at sites outside clusters. At some loci, Mael repression requires the piRNA pathway, while at others, piRNAs play no role. We propose that by repressing canonical transcription of individual transposon mRNAs, Mael helps Rhi drive non-canonical transcription of piRNA precursors without generating mRNAs encoding transposon proteins.

Original languageEnglish (US)
Pages (from-to)291-303.e6
JournalMolecular Cell
Volume73
Issue number2
DOIs
StatePublished - Jan 17 2019

Keywords

  • Argonaute
  • Armitage
  • Maelstrom
  • piRNA
  • Piwi
  • PIWI-interacting RNA
  • Rhino
  • small silencing RNA
  • transcription
  • transposon

ASJC Scopus subject areas

  • Molecular Biology
  • Cell Biology

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