Cell Reports
Volume 33, Issue 6, 10 November 2020, 108380
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Article
Modulation of Ago2 Loading by Cyclophilin 40 Endows a Unique Repertoire of Functional miRNAs during Sperm Maturation in Drosophila

https://doi.org/10.1016/j.celrep.2020.108380Get rights and content
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Highlights

  • Hsp90 co-chaperone Cyp40 plays essential roles for sperm maturation in flies

  • Ago2 sorting and arm switching generate a functional miRNA in testes

  • Conserved affinity of Cyp40 for small RNA duplex-binding Ago proteins

  • Selective requirement of Cyp40 for the expression of Ago2-sorted miRNAs

Summary

In gene silencing, Hsp90 chaperone machinery assists Argonaute (Ago) binding and unwinding of silencing small RNA (sRNA) duplexes. This enables the formation of effector RNA-induced silencing complex (RISC) that often displays cargo preferences. Hence, in Drosophila, microRNAs (miRNAs) and small-interfering RNAs (siRNAs) are differentially sorted into Ago1-RISC and Ago2-RISC, respectively. Here, we identify fly Cyclophilin 40 (Cyp40) as a testis-specialized Hsp90 co-chaperone essential for spermatogenesis and for modulating Ago2-RISC formation. We show that testis-distinctive Ago-sorting and strand-selection mechanisms accumulate a unique set of miRNAs on Ago2. Cyp40 interacts with duplex-incorporating Ago2 through Hsp90 in vitro and selectively promotes the build-up of Ago2-bound miRNAs, but not endogenous siRNAs, in vivo. Moreover, one of Cyp40-dependent Ago2-sorted miRNAs is required for late spermatogenesis, unraveling the physiological relevance of the unconventional yet conserved Drosophila miRNA-Ago2 sorting pathway. Collectively, these results identify RISC-regulatory roles for Hsp90 machinery and, more generally, highlight the tissue-specific adaptation of sRNA pathways through chaperone diversification.

Keywords

spermatogenesis
gene silencing
Argonaute
microRNA
chaperone
Hsp90
Cyclophilin 40
Cyp40/PPID
germline
Drosophila

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