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Genes Dev. 2019 Mar 1;33(5-6):348-364. doi: 10.1101/gad.320796.118. Epub 2019 Feb 26.

RNAi-dependent Polycomb repression controls transposable elements in Tetrahymena.

Author information

1
Department of Pathology, University of Michigan, Ann Arbor, Michigan 48109, USA.
2
Institute of Evolution and Marine Biodiversity, Ocean University of China, Qingdao 266003, China.
3
Key Laboratory of Aquatic Biodiversity and Conservation, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China.
4
Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266003, China.
5
Department of Human Genetics, University of Utah School of Medicine, Salt Lake City, Utah 84112, USA.
6
Department of Molecular Biology and Genetics, Cornell University, Ithaca, New York 14850, USA.
7
J. Craig Venter Institute, Rockville, Maryland 20850, USA.
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Contributed equally

Abstract

RNAi and Polycomb repression play evolutionarily conserved and often coordinated roles in transcriptional silencing. Here, we show that, in the protozoan Tetrahymena thermophila, germline-specific internally eliminated sequences (IESs)-many related to transposable elements (TEs)-become transcriptionally activated in mutants deficient in the RNAi-dependent Polycomb repression pathway. Germline TE mobilization also dramatically increases in these mutants. The transition from noncoding RNA (ncRNA) to mRNA production accompanies transcriptional activation of TE-related sequences and vice versa for transcriptional silencing. The balance between ncRNA and mRNA production is potentially affected by cotranscriptional processing as well as RNAi and Polycomb repression. We posit that interplay between RNAi and Polycomb repression is a widely conserved phenomenon, whose ancestral role is epigenetic silencing of TEs.

KEYWORDS:

Polycomb repression; RNAi; transposable elements

PMID:
30808657
DOI:
10.1101/gad.320796.118

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