FBSコロキウム 285回生殖生物学研究室
| 講演 |
1. Molecular basis of Nuage organization by Tejas for piRNA biogenesis in Drosophila Lin Yuxuan［甲斐研・D5］ 2. The Tudor domain-containing protein, Kotsubu, is developmentally regulated in the male germline and required for proper piRNA biogenesis in D. melanogaster. Lim Lin Xenia ［甲斐研・D4］ |
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| 日時 | 2021年11月18日（木）12:15〜13:00 |
| 場所 | Zoomでのオンラインセミナーとなります：参加に必要なミーティングリンク、ID、パスワードは事前に、関係者へメールにてご連絡致します。 |
| 言語 | 英語 |
| 世話人 |
河口真一 助教 |
1. Molecular basis of Nuage organization by Tejas for piRNA biogenesis in Drosophila
In Drosophila germline cells, the piRNA amplification, called the ping-pong cycle, takes place at perinuclear structure nuage. Two PIWI-clade Argonaute proteins, Aubergine (Aub) and Argonaute3 (Ago3) alternately bind and slice the piRNA precursors and TE transcripts into piRNAs assisted by other components localized to nuage, such as Tejas (Tej) and Spindle-E (Spn-E), fly homologs of Tdrd5 and Tdrd9. Tej and Spn-E are indispensable for piRNA ping-pong amplification, but the molecular basis of how they cooperate in this processing remains elusive. High-resolution imaging of ovaries containing endogenously fluorescent-tagged SpnE, Vas, Ago3, and Aub revealed a clear defect in the localization of several piRNA factors.
Among those, core helicase Vas lost its granulation meanwhile the function unknown helicase SpnE displayed a unique nuclear accumulation in tej mutant ovaries. In the absence of Tej, the piRNA precursors accumulated, and Aub and Ago3 bound piRNAs were massively reduced. Loss-of-Spn-E or Vas ovaries exhibited a similar accumulation of piRNA precursors as in Tej. Our structure-function experiments showed the distinct domains of Tej will recruit the corresponding helicase, also revealed the disorder region of Tej will contribute to the condensate formation, which will enhance the mobility of Vas in Nuage granules.
Taken together, our data suggested that Tej regulates the dynamics of Spn-E and Vas as an aggregator for nuage, takes a key role in the secondary piRNA precursor processing.
2. The Tudor domain-containing protein, Kotsubu, is developmentally regulated in the male germline and required for proper piRNA biogenesis in D. melanogaster.
Silencing of Transposable elements (TEs) by Piwi-interacting RNAs (piRNAs) is crucial in maintaining germline genome integrity and fertility of an animal. To repress TEs, PIWI-clade Argonaute proteins cooperate with Tudor domain-containing proteins at membraneless perinuclear organelles, called nuage, producing piRNAs to repress transposons. Here, we identify and characterize one of the Drosophila Tdrd1 orthologues, Kotsubu (Kots), which is a Tudor domain-containing protein. We show the dynamic localisation of Kots in the male germline wherein Kots is found at the nuage in spermatogonia. In addition, Kots forms large cytoplasmic condensates in the spermatocytes that overlaps with piNG-body components, a nuage-associated organelle. The loss of kots resulted in a notable upregulation of stellate and a corresponding reduction in the Suppressor of Stellate piRNAs in the mutants. Furthermore, a moderate yet significant reduction of other piRNAs was observed in kots mutant testes, albeit to a weaker extent in mutant ovaries. Taken together, we propose that Kots functions in the piRNA pathway, predominantly in the male germline by forming discrete cytoplasmic granules.
