replication-born double-strand break repair via sister chromatid exchange

Definition

Target type: biologicalprocess

The repair of a replication-born double-strand DNA break in which the DNA molecule is repaired using the homologous sequence of the sister chromatid which serves as a template to repair the breaks. [GOC:rb, PMID:12820977, PMID:16888651]

Replication-born double-strand break (DSB) repair via sister chromatid exchange (SCE) is a crucial mechanism that ensures genome integrity during DNA replication. This process occurs when a DSB arises during replication fork progression, posing a significant threat to cell viability. Here's a detailed description of the steps involved:

1. **DSB formation:** During replication, a DSB can occur due to various factors, including replication fork stalling, collisions with other DNA structures, or encountering DNA damage.
2. **Replication fork collapse:** The DSB triggers the collapse of the replication fork, leading to a stalled replication process.
3. **5'-3' resection:** The 5' ends of the DSB are processed by nucleases, creating 3' single-stranded tails.
4. **RAD51-mediated strand invasion:** The 3' tails of the broken DNA strand invade the homologous sister chromatid, pairing with the corresponding sequence.
5. **Branch migration:** The invading strand displaces the homologous strand on the sister chromatid, forming a Holliday junction. This process extends the region of pairing between the broken and sister chromatid DNA.
6. **DNA synthesis:** Using the sister chromatid as a template, DNA polymerase synthesizes new DNA on the broken strand, extending from the point of invasion.
7. **Holliday junction resolution:** The Holliday junction is resolved by specific enzymes, creating two distinct DNA molecules. This resolution can occur in two ways, resulting in either a cross-over or non-cross-over event.
8. **Cross-over or non-cross-over:** In a cross-over event, the sister chromatids exchange genetic material, resulting in recombination between the two chromosomes. In a non-cross-over event, the original chromosome sequences are restored without any exchange of genetic material.

Overall, replication-born DSB repair via SCE is a complex process that requires the coordinated action of numerous proteins. This pathway is essential for maintaining genomic stability by allowing the repair of DNA damage that occurs during replication. Without SCE, DSBs could lead to chromosome rearrangements, gene loss, and ultimately, cell death.'
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Proteins (1)

Compounds (4)