Tailed duplex DNA is the preferred substrate for Rad51 protein-mediated homologous pairing

Alexander V. Mazin, Elena Zaitseva, Patrick Sung, Stephen C. Kowalczykowski

Research output: Contribution to journalArticlepeer-review

138 Scopus citations


The repair of potentially lethal DNA double-stranded breaks (DSBs) by homologous recombination requires processing of the broken DNA into a resected DNA duplex with a protruding 3'-single-stranded DNA (ssDNA) tail. Accordingly, the canonical models for DSB repair require invasion of an intact homologous DNA template by the 3'-end of the ssDNA, a characteristic that the bacterial pairing protein RecA possesses. Unexpectedly, we find that for the eukaryotic homolog, Rad51 protein, the 5'-end of ssDNA is more invasive than the 3'-end. This pairing bias is unaffected by Rad52, Rad54 or Rad55-57 proteins. However, further investigation reveals that, in contrast to RecA protein, the preferred DNA substrate for Rad51 protein is not ssDNA but rather dsDNA with ssDNA tails. This important distinction permits the Rad51 proteins to promote DNA strand invasion using either 3'- or 5'-ends with similar efficiency.

Original languageEnglish (US)
Pages (from-to)1148-1156
Number of pages9
JournalEMBO Journal
Issue number5
StatePublished - Mar 1 2000
Externally publishedYes


  • DNA strand exchange
  • Homologous recombination
  • Joint molecule formation

ASJC Scopus subject areas

  • General Immunology and Microbiology
  • General Biochemistry, Genetics and Molecular Biology
  • Molecular Biology
  • General Neuroscience


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