The Drosophila HP1 Homolog Rhino Is Required for Transposon Silencing and piRNA Production by Dual-Strand Clusters

• Published in: Cell Vol. 138; no. 6; pp. 1137 - 1149
• Main Authors: Klattenhoff, Carla, Xi, Hualin, Li, Chengjian, Lee, Soohyun, Xu, Jia, Khurana, Jaspreet S., Zhang, Fan, Schultz, Nadine, Koppetsch, Birgit S., Nowosielska, Anetta, Seitz, Herve, Zamore, Phillip D., Weng, Zhiping, Theurkauf, William E.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 18-09-2009
• Subjects: Animals; Chromatin Immunoprecipitation; Chromosomal Proteins, Non-Histone - metabolism; DNA Transposable Elements; Drosophila; Drosophila melanogaster - genetics; Drosophila melanogaster - metabolism; Drosophila Proteins - metabolism; Gene Silencing; Heterochromatin - metabolism; RNA; RNA, Small Interfering - metabolism; STEMCELL; Transcription, Genetic; RNA; STEMCELL
• ISSN: 0092-8674; 1097-4172
• DOI: 10.1016/j.cell.2009.07.014

Piwi-interacting RNAs (piRNAs) silence transposons and maintain genome integrity during germline development. In Drosophila, transposon-rich heterochromatic clusters encode piRNAs either on both genomic strands (dual-strand clusters) or predominantly one genomic strand (uni-strand clusters). Primary piRNAs derived from these clusters are proposed to drive a ping-pong amplification cycle catalyzed by proteins that localize to the perinuclear nuage. We show that the HP1 homolog Rhino is required for nuage organization, transposon silencing, and ping-pong amplification of piRNAs. rhi mutations virtually eliminate piRNAs from the dual-strand clusters and block production of putative precursor RNAs from both strands of the major 42AB dual-strand cluster, but not of transcripts or piRNAs from the uni-strand clusters. Furthermore, Rhino protein associates with the 42AB dual-strand cluster,but does not bind to uni-strand cluster 2 or flamenco. Rhino thus appears to promote transcription of dual-strand clusters, leading to production of piRNAs that drive the ping-pong amplification cycle.