Open Close
Reference
Citation
Yin, H., Lin, H. (2007). An epigenetic activation role of Piwi and a Piwi-associated piRNA in Drosophila melanogaster.  Nature 450(7167): 304--308.
FlyBase ID
FBrf0202885
Publication Type
Research paper
Abstract

Heterochromatin, representing the silenced state of transcription, consists largely of transposon-enriched and highly repetitive sequences. Implicated in heterochromatin formation and transcriptional silencing in Drosophila are Piwi (P-element induced wimpy testis) and repeat-associated small interfering RNAs (rasiRNAs). Despite this, the role of Piwi in rasiRNA expression and heterochromatic silencing remains unknown. Here we report the identification and characterization of 12,903 Piwi-interacting RNAs (piRNAs) in Drosophila, showing that rasiRNAs represent a subset of piRNAs. We also show that Piwi promotes euchromatic histone modifications and piRNA transcription in subtelomeric heterochromatin (also known as telomere-associated sequence, or TAS), on the right arm of chromosome 3 (3R-TAS). Piwi binds to 3R-TAS and a piRNA uniquely mapped to 3R-TAS (3R-TAS1 piRNA). In piwi mutants, 3R-TAS loses euchromatic histone modifications yet accumulates heterochromatic histone modifications and Heterochromatin Protein 1a (HP1a). Furthermore, the expression of both the 3R-TAS1 piRNA and a white reporter gene in 3R-TAS becomes suppressed. A P element inserted 128 base pairs downstream of the 3R-TAS1 piRNA coding sequence restores the euchromatic histone modifications of 3R-TAS and the expression of 3R-TAS1 piRNA in piwi mutants, as well as partly rescuing their defects in germline stem-cell maintenance. These observations suggest that Piwi promotes the euchromatic character of 3R-TAS heterochromatin and its transcriptional activity, opposite to the known roles of Piwi and the RNA-mediated interference pathway in epigenetic silencing. This activating function is probably achieved through interaction with at least 3R-TAS1 piRNA and is essential for germline stem-cell maintenance.

PubMed ID
PubMed Central ID
Associated Information
Comments
Associated Files
Other Information
Secondary IDs
    Language of Publication
    English
    Additional Languages of Abstract
    Parent Publication
    Publication Type
    Journal
    Abbreviation
    Nature
    Title
    Nature
    Publication Year
    1869-
    ISBN/ISSN
    0028-0836
    Data From Reference
    Alleles (3)
    Genes (8)
    Natural transposons (2)
    Insertions (1)
    Transgenic Constructs (1)