Siwi cooperates with Par-1 kinase to regulate mitochondrial Papi scaffolding Siwi-piRISC biogenesis
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ABSTRACT: Bombyx Papi contains two K-homology (KH) domains and one Tudor domain, and acts as a scaffold for Siwi-piRISC biogenesis on the mitochondrial surface. To initiate this process, Papi binds first to Siwi via the Tudor domain and subsequently to piRNA precursors loaded onto Siwi via the KH domains. This second action depends on phosphorylation of Papi. However, its underlying mechanism remains unknown. Here, we show that Siwi targets Par-1 kinase to mitochondrial Papi to promote its phosphorylation at Ser547 in the auxiliary domain and that this modification enhances the ability of Papi to bind Siwi-bound piRNA precursors via the KH domains. Papi S547A mutant still bound to Siwi, like wild-type (WT) Papi, although it evaded phosphorylation by Par-1: Consequently, Papi lost the ability to bind RNAs, abrogating the generation of Siwi-piRISC. Papi mutant lacking the Tudor and auxiliary domains escaped coordinated regulation by Siwi and Par-1 and lost their bias to bind piRNA precursors. Pseudo-phosphorylation mutants of Papi restored Siwi-piRISC formation in Papi-lacking cells, but their ability to bind RNAs required Siwi, similar to WT Papi. Par-1-dependent, multilayered mechanism by which Siwi regulates the role of Papi in Siwi-piRISC biogenesis was revealed.
ORGANISM(S): Bombyx mori
PROVIDER: GSE179432 | GEO | 2022/01/25
REPOSITORIES: GEO
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