title: Respective functions of two distinct Siwi complexes assembled during PIWI-interacting RNA biogenesis in Bombyx germ cells.
abstract: PIWI-interacting RNA (piRNA) biogenesis consists of two sequential steps: primary piRNA processing and the ping-pong cycle that depends on reciprocal Slicer-mediated RNA cleavage by PIWI proteins. However, the molecular functions of the factors involved remain elusive. Here, we show that RNAs cleaved by a Bombyx mori PIWI, Siwi, remain bound to the protein upon cleavage but are released by a DEAD box protein BmVasa. BmVasa copurifies with Siwi but not another PIWI BmAgo3. A lack of BmVasa does not affect primary piRNA processing but abolishes the ping-pong cycle. Siwi also forms a complex with BmSpn-E and BmQin. This complex is physically separable from the Siwi/BmVasa complex. BmSpn-E, unlike BmVasa, is necessary for primary piRNA production. We propose a model for piRNA biogenesis, where the BmSpn-E/BmQin dimer binds Siwi to function in primary piRNA processing, whereas BmVasa, by associating with Siwi, ensures target RNA release upon cleavage to facilitate the ping-pong cycle.
authors.affiliation: Graduate School of Science, The University of Tokyo, Tokyo 113-0032, Japan.
authors.forename: Kazumichi M
authors.initials: KM
authors.lastname: Nishida
authors.affiliation: Keio University School of Medicine, Tokyo 160-8582, Japan.
authors.forename: Yuka W
authors.initials: YW
authors.lastname: Iwasaki
authors.affiliation: Graduate School of Science, The University of Tokyo, Tokyo 113-0032, Japan.
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Murota
authors.affiliation: Keio University School of Medicine, Tokyo 160-8582, Japan.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Nagao
authors.affiliation: Keio University School of Medicine, Tokyo 160-8582, Japan.
authors.forename: Taro
authors.initials: T
authors.lastname: Mannen
authors.affiliation: Graduate School of Science, The University of Tokyo, Tokyo 113-0032, Japan.
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Kato
authors.affiliation: Keio University School of Medicine, Tokyo 160-8582, Japan.
authors.forename: Haruhiko
authors.initials: H
authors.lastname: Siomi
authors.affiliation: Graduate School of Science, The University of Tokyo, Tokyo 113-0032, Japan. Electronic address: siomim@bs.s.u-tokyo.ac.jp.
authors.forename: Mikiko C
authors.initials: MC
authors.lastname: Siomi
mesh_terms: D000818:Animals; D012831:Bombyx / Q000235:genetics / Q000378:metabolism*; D053487:DEAD-box RNA Helicases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D005854:Germ Cells / Q000166:cytology / Q000378:metabolism*; D011485:Protein Binding; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000378:metabolism*
chemical_list: D034741:RNA, Small Interfering; D053487:DEAD-box RNA Helicases