Homologous recombination (HR) uses a homologous template to accurately repair DNA double-strand breaks and stalled replication forks to maintain genome stability. During homology search, RAD51 nucleoprotein filaments probe and interact with dsDNA, forming the synaptic complex that is stabilized on a homologous sequence. Strand intertwining leads to the formation of a displacement-loop (D-loop). In yeast, RAD54 is essential for HR in vivo and required for D-loop formation in vitro, but its exact role remains to be fully elucidated. Using electron microscopy to visualize the DNA-protein complexes, here we find that RAD54 is crucial for RAD51-mediated synaptic complex formation and homology search. The RAD54-K341R ATPase-deficient mutant protein promotes formation of synaptic complexes but not D-loops and leads to the accumulation of stable heterologous associations, suggesting that the RAD54 ATPase is involved in preventing non-productive intermediates. We propose that RAD51/RAD54 form a functional unit operating in homology search, synaptic complex and D-loop formation.

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Journal Article | Research Support, N.I.H., Extramural | Research Support, Non-U.S. Gov't

Authors

Tavares EM, Wright WD, Heyer WD, Le Cam E, Dupaigne P

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