Additionally, XRCC3 complex capped filaments promote D-loop formation — a key HR intermediate for repairing DSBs and stalled forks.

This shows that capping by the XRCC3 complex directly enhances RAD51’s synaptic activity. (7/8)

XRCC3 remodels the terminal RAD51 N-terminal domain to bind in trans.

This rearrangement is conserved in archaeal paralog RadB and yeast paralog complex Rad55–Rad57, revealing a deeply conserved filament-capping mechanism. (6/8)

Using cryo-EM, single-molecule and biochemical assays ❄️💡, we found these two tetramers functionally differ:

➡️ The RAD51B complex assembles RAD51 filaments in an ATP hydrolysis–coupled, dynamic manner.
➡️ The XRCC3 complex caps the 5′ ends of RAD51 filaments – independent of ATP hydrolysis (5/8)

It is known that the five RAD51 paralogs exist as a tetramer (RAD51B-C-D-XRCC2) and dimer (RAD51C-XRCC3). Our data overturn this paradigm:

➡️ The ‘dimer’ actually exists in a tetrameric XRCC3 complex: XRCC3-RAD51C-RAD51D-XRCC2.
➡️ Therefore, there are two near-identical tetrameric assemblies.

‼️ Excited to share our new paper out now in @science.org ‼️

We describe a new tetrameric RAD51 paralog complex – XRCC3-RAD51C-RAD51D-XRCC2 – which caps the end of RAD51 filaments.

Link: www.science.org/doi/epdf/10....

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A photo from the recombination mechanisms conference in Crete last week. Thanks to the @fusionconf.bsky.social team, speakers, poster presenters and attendees for a great meeting!