Great Aude! Just an update, we have our own website:
www.swartslab.org

Also I am not sure when I stop being an early career scientist 🤐

Congratulations Daniel! Fantastic :D

Congrats Fabai 👏!

We are excited and grateful that the main authors thought that prokaryotic Argonaute proteins were a cool target to design binders for, and that we could contribute to this paper. We will continue using BindCraft to further probe our proteins of interest!

Congrats Jorge, fantastic!

In addition @sumanthmutte.bsky.social , @tniault.bsky.social @patrickbarendse.bsky.social @belkoopal.bsky.social and many blueskyless co-authors. Also with further help of collaborator @hauryliuk.bsky.social!

Thanks to all who contributed to this multidisciplinary study!

The first steps of this work were taken a long time ago during my @embo.org fellowship in the Jinek lab @martinjinek.bsky.social, but the main work was carried out by the talented Pilar Bobadilla Ugarte in our group @bic-wur.bsky.social @w-u-r.bsky.social funded by @erc.europa.eu .

This suggests that in absence of repair complexes, pAgos need ACE to generate guide DNAs.

These findings corroborate the importance of RecBCD/AddAB for long-A pAgos and highlights the versatility of immune systems to adapt to distinct hosts with different accessory proteins.

hat is the relevance of ACE? Jolly et al. and Kuzmenko et al., demonstrated that DNA repair complexes AddAB/RecBCD are major drivers of guide DNA generation for long-A pAgos.

In another study, we recently showed that cyanobacteria lack RecBCD/AddAB:
sciencedirect.com/science/arti...

But what does it mean in vivo? We show that, in E. coli, while the cyanobacterial pAgo alone can provide defense against plasmids and phages, ACE can enhance the interference phenotype (at least for plasmids) demonstrating these proteins function in conjunction.

Co-expression of the cyanobacterial pAgo and ACE in E. coli reveals that pAgo-associated guide DNAs are (further) processed (shortened) by ACE. We show that longer guide DNAs are not functional, which shows that ACE contributes to guide DNA generation in coli.

The cyanobacterial pAgo and its ACE partner form a heterodimeric complex in which activity of ACE1 is modulated. But this still leaves a question: Is ACE1 important for guide generation or (further) target DNA a degradation?

Structural and biochemical characterization of ACE shows it is a DNA nuclease. Its catalytic site is buried in a channel that can only be accessed by single stranded DNA. Analysis of sequencing products show that ACE preferentially cleaves ssDNA upstream of guanine residues.

Investigation of the cyanobacterial pAgos shows that they are DNA-guided DNA cleaving pAgos, akin to various other long-A pAgos (TtAgo, CbAgo, PfAgo).

Those experiments as well as the crystal structure of CtAgo do not reveal why they would need ACE as partner.

Cyanobacterial long-A pAgos are co-encoded with Cas4 family proteins (from hereon: ACE for Argonaute associated Cas4-like enzyme).

Our analysis shows that despite their family name, ACEs look more like the nuclease domains of AdnAB and AddAB than like CRISPR-Cas4.

Various long-A pAgos act as stand-alone immune systems. They utilize small DNA guides to recognize and cleave target DNA.

Certain long-A pAgos are co-encoded with accessory proteins, which suggests these proteins function in conjunction. What is the need of these proteins? 🤔

www.cell.com/cell-reports...

And this one...