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Virginia Busetto

@virginiabusetto.bsky.social

Postdoc in the Falk lab @Max Perutz Labs Vienna

Virginia Busetto @virginiabusetto.bsky.social · 08/09/2026

I’m also grateful to @fwf-at.bsky.social -especially the ESPRIT programme- for supporting me, and to @maxperutzlabs.ac.at, @univie.ac.at and the @viennabiocenter.bsky.social.

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Virginia Busetto @virginiabusetto.bsky.social · 08/09/2026

Huge thanks to my mentor @sebastianfalk.bsky.social, all co-authors, and our collaborators in the @ameressl.bsky.social and @reneketting.bsky.social labs.

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Virginia Busetto @virginiabusetto.bsky.social · 08/09/2026

Strikingly, CPUG resembles the cleavage and polyadenylation (CPA) complex: both pair an active nuclease with an inactive paralog and a nucleotidyltransferase, activating cleavage only after assembly. A similar architectural strategy for very different problems and very different RNA fates.

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Virginia Busetto @virginiabusetto.bsky.social · 08/09/2026

Finally, how does CPUG ensure directionality and protect the RNA from re-cleavage? Two ways: RNA engagement by MUT-2 limits RDE-8 access, and RDE-8 sequence preference spares the new poly(UG) tail. Together, these features keep the reaction moving forward.

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Virginia Busetto @virginiabusetto.bsky.social · 08/09/2026

After cleavage, MUT-2 -the remarkable CPUG nucleotidyltransferase- adds long, alternating poly(UG) tails. Using high-throughput sequencing, we found that the RNA 3′ end influences both tailing efficiency and the register of the UG repeat.

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Virginia Busetto @virginiabusetto.bsky.social · 08/09/2026

Is MUT-15 more than a scaffold? Could it also activate RDE-8, ensuring that cleavage occurs only when the full machinery is assembled? It does: MUT-15 binds RNA, remodels the nuclease module, and licenses RDE-8 cleavage.

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Virginia Busetto @virginiabusetto.bsky.social · 08/09/2026

At the center of CPUG is MUT-15, which connects the RDE-8/NYN-1 nuclease module to the poly(UG) polymerase MUT-2. MUT-15 has the two RecA-like domains characteristic of DEAD-box helicases but lacks ATPase activity: it is a pseudohelicase!

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Virginia Busetto @virginiabusetto.bsky.social · 08/09/2026

RNA cleavage is irreversible and potentially dangerous, so RDE-8 -the endoribonuclease of CPUG- must be tightly controlled. We found that RDE-8 forms an autoinhibited heterodimer with the pseudonuclease NYN-1, keeping cleavage restrained until CPUG assembles.

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Virginia Busetto @virginiabusetto.bsky.social · 08/09/2026

In C. elegans, RNA cleavage and poly(UG)ylation mark Argonaute-targeted transcripts as templates for secondary small-RNA production, enabling efficient and robust RNAi. We biochemically reconstituted the machinery responsible: the cleavage and poly(UG)ylation (CPUG) complex.

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Virginia Busetto @virginiabusetto.bsky.social · 08/09/2026

Very excited to share our new preprint: “A pseudohelicase-centered complex couples assembly-dependent RNA cleavage to poly(UG)ylation”! 🎉 Want to know more? 🧵👇 www.biorxiv.org/content/10.6...

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