Respective functions of two distinct siwi complexes assembled during PIWI-interacting RNA biogenesis in bombyx germ cells

Kazumichi M. Nishida, Yuka W. Iwasaki, Yukiko Murota, Akihiro Nagao, Taro Mannen, Yumiko Kato, Haruhiko Siomi, Mikiko C. Siomi

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47 Citations (Scopus)


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.

Original languageEnglish
Pages (from-to)193-203
Number of pages11
JournalCell Reports
Issue number2
Publication statusPublished - 2015 Jan 13


ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)

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