Molecular Life Sciences

Living Edition
| Editors: Robert D. Wells, Judith S. Bond, Judith Klinman, Bettie Sue Siler Masters, Ellis Bell

Single-Strand Annealing

  • Sang Eun Lee
Living reference work entry


Single-strand annealing (SSA) repairs DNA double-strand breaks (DSBs) by annealing tandem repeat sequences flanking the DSB, thereby deleting one of the repeats and the intervening sequence. The precise steps of SSA are not fully defined yet, but the basic framework and genetic requirements are described in budding yeast. Here, I will summarize the genetics and molecular mechanisms of SSA in yeast and higher eukaryotes.


Single-strand annealing (SSA) is a highly mutagenic but efficient DSB repair mechanism (Paques and Haber 1999). It relies on the presence of tandem repeat sequences flanking a DNA break to anneal and repair the DSB (Fig. 1). The initial step of SSA in yeast is the formation of single-stranded DNA (ssDNA) by the actions of multiple nucleases and helicases. Species-specific homologous proteins catalyze end resection in higher eukaryotes. The next step involves annealing of the repeat sequences, located up to 20–30 kilobases flanking DNA break, and...


Tandem Repeat Sequence Annealed Intermediate Homologous Recombination Pathway Recombination Intermediate Collapse Replication Fork 
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Copyright information

© Springer Science+Business Media New York 2014

Authors and Affiliations

  1. 1.Department of Molecular MedicineUniversity of Texas Health Science CenterSan AntonioUSA