double-strand break repair via single-strand annealing

Definition

Target type: biologicalprocess

Repair of a DSB made between two repeated sequences oriented in the same direction occurs primarily by the single strand annealing pathway. The ends of the break are processed by a 5' to 3' exonuclease, exposing complementary single-strand regions of the direct repeats that can anneal, resulting in a deletion of the unique DNA between the direct repeats. [PMID:11606529]

Double-strand break (DSB) repair via single-strand annealing (SSA) is a specialized pathway that operates when two broken DNA ends share a region of homology. This pathway is particularly relevant for repairing DSBs that occur within repetitive sequences, where other repair pathways might lead to incorrect rejoining. Here's a detailed breakdown of the process:

1. **Resection:** The 5' ends of the broken DNA strands are resected by nucleases, removing nucleotides and creating 3' single-stranded overhangs.
2. **Strand Invasion:** The 3' overhang of one broken end invades the complementary sequence on the other broken end, forming a displacement loop (D-loop).
3. **Annealing:** The invading strand anneals with the complementary sequence, bringing the two broken ends together.
4. **DNA Synthesis:** DNA polymerase fills in the gaps in the newly annealed strands, extending them to complete the missing sequence.
5. **Ligation:** DNA ligase seals the remaining nick in the DNA backbone, joining the two strands and completing the repair.

SSA relies on the presence of homologous sequences flanking the break, facilitating the annealing process. This pathway is highly accurate in restoring the original DNA sequence, as it relies on the complementary base pairing of the homologous regions. However, it can also lead to deletions if the homologous regions are not perfectly aligned.

SSA is an important backup pathway for DSB repair, particularly in situations where other pathways are not efficient, like in repetitive DNA sequences. However, its reliance on homologous sequences makes it less versatile than other repair pathways.'
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Proteins (1)

Compounds (17)