Abstract
AddAB is a helicase-nuclease that processes
double-stranded DNA breaks for repair by homologous
recombination. This process is modulated by
Chi recombination hotspots: specific DNA sequences
that attenuate the nuclease activity of the
translocating AddAB complex to promote downstreamrecombination. Using a combination of kinetic and imaging techniques, we show that AddAB translocation is not coupled to DNA unwinding in the absence of single-stranded DNA binding proteins
because nascent single-stranded DNA immediately
re-anneals behind the moving enzyme. However,
recognition of recombination hotspot sequences
during translocation activates unwinding by coupling these activities, thereby ensuring the downstream formation of single-stranded DNA that is required for RecA-mediated recombinational repair. In addition to their implications for the mechanism of double-stranded DNA break repair, these observations may affect our implementation and interpretation of helicase assays and our understanding of helicase mechanisms in general.
Translated title of the contribution | Recombination hotspots and single-stranded DNA binding proteins couple DNA translocation to DNA unwinding by the AddAB helicase-nuclease |
---|---|
Original language | English |
Pages (from-to) | 806 - 816 |
Number of pages | 11 |
Journal | Molecular Cell |
Volume | 42 |
Issue number | 6 |
DOIs | |
Publication status | Published - Jun 2011 |