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
University of Massachusetts Medical School, Worcester, MA 01605, USA.
Cell. 2009 Sep 18;138(6):1137-49. doi: 10.1016/j.cell.2009.07.014. Epub 2009 Sep 3.
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.
Piwi相互作用RNA（piRNA）在生殖系发育过程中沉默转座子并维持基因组完整性。在果蝇中，富含转座子的异染色质簇在两条基因组链上（双链簇）或主要在一条基因组链上（单链簇）编码piRNA。源自这些簇的初级piRNA被认为驱动由定位于核周生殖质的蛋白质催化的乒乓扩增循环。我们发现HP1同源物Rhino是生殖质组织、转座子沉默和piRNA的乒乓扩增所必需的。rhi突变几乎从双链簇中消除了piRNA，并阻断了主要的42AB双链簇两条链上假定前体RNA的产生，但不影响单链簇的转录本或piRNA的产生。此外，Rhino蛋白与42AB双链簇相关，但不与单链簇2或弗拉门戈结合。因此，Rhino似乎促进双链簇的转录，导致驱动乒乓扩增循环的piRNA的产生。
