Distinct pathways of homologous recombination controlled by the SWS1–SWSAP1–SPIDR complex

Abstract

Homology-directed repair (HDR), a critical DNA repair pathway in mammalian cells, is complex, leading to multiple outcomes with different impacts on genomic integrity. However, the factors that control these different outcomes are often not well understood. Here we show that SWS1–SWSAP1-SPIDR controls distinct types of HDR. Despite their requirement for stable assembly of RAD51 recombinase at DNA damage sites, these proteins are not essential for intra-chromosomal HDR, providing insight into why patients and mice with mutations are viable. However, SWS1–SWSAP1-SPIDR is critical for inter-homolog HDR, the first mitotic factor identified specifically for this function. Furthermore, SWS1–SWSAP1-SPIDR drives the high level of sister-chromatid exchange, promotes long-range loss of heterozygosity often involved with cancer initiation, and impels the poor growth of BLM helicase-deficient cells. The relevance of these genetic interactions is evident as SWSAP1 loss prolongs Blm-mutant embryo survival, suggesting a possible druggable target for the treatment of Bloom syndrome.

C1orf112 is a novel regulator of interstrand crosslink that decreases FIGNL1-RAD51 interaction

“…Although RAD51 was recently involved in the protection of cells from transcription-replication conflicts 41 , either C1orf112- or FIGNL1-depleted cells are not sensitized to transcription-interfering agents such as Trabectedin and illudinS ( Fig S6 ), suggesting that the heterodimer specifically regulates RAD51 dynamics following strand invasion and not at stalled replication forks per se. Interestingly, cells depleted from either one of these factors are specifically sensitive to chemical agents that generate replication roadblocks, which requires a specific processing before repair such as ICL-agents and agents that promote either base oxidation or base alkylation ( Fig S6 ) 42–44 Of note, our data suggest that C1orf112 and the SWS1-SWSAP1-SPIDR complex, which inhibit FIGNL1-dependent RAD51 unloading 9,10 , play opposite roles in response to replication stress. Consistently, both complexes cluster differently when analysed by chemogenomic profiling ( Fig S6 ).…”

“…Aside from a better understanding of ICL repair pathway choice, several reports have highlighted the complexity of the final stages of ICL repair, such as the resolution of RAD51-mediated strand invasion. For instance, the AAA + ATPase FIGNL1 has been shown to bind RAD51 and promote its unloading from DNA 9 , a function that is limited by the SWSAP1-SWS1-SPIDR complex 9,10 . More recently, the helicase HELQ 11 and the HROB–MCM8–MCM9 12 complex have been shown to contribute to parallel pathways that promote DNA repair synthesis following D-loop formation.…”

The role and mechanism of long non‐coding RNAs in homologous recombination repair of radiation‐induced DNA damage

“…Once the nucleoprotein filament is formed, it is able to search for homologous sequences within the genomic double-stranded DNA (dsDNA) to identify a sister chromatid to use as a repair template. 26 Upon identification of a homologous sequence, the nucleoprotein filament invades the dsDNA donor duplex and replaces the original strand, resulting in the displacement of a template DNA strand to form a D-loop. This D-loop includes both the new heterologous dsDNA and the shifted original donor DNA strand, and is combined by base pairing between complementary sequences.…”

“…Synapsis: The RAD51‐ssDNA nucleoprotein filament‐mediated homologous sequence search and DNA strand invasion are the core reactions of HR repair. Once the nucleoprotein filament is formed, it is able to search for homologous sequences within the genomic double‐stranded DNA (dsDNA) to identify a sister chromatid to use as a repair template 26 . Upon identification of a homologous sequence, the nucleoprotein filament invades the dsDNA donor duplex and replaces the original strand, resulting in the displacement of a template DNA strand to form a D‐loop.…”

Molecular Underpinnings and Environmental Drivers of Spontaneous Loss of Heterozygosity in Drosophila Intestinal Stem Cells

“…Break-induced replication, on the other hand, involves errorprone synthesis of large portions of chromosomes resulting in LOH of heterozygous alleles within the copied region [25,28]. Studies in mammalian cell culture and in Drosophila germline cells have provided additional insight into molecular mechanisms of mitotic recombination and indicated a large degree of conservation of enzymes and processes [31][32][33][34][35][36][37]. In particular, Drosophila studies revealed that mitotic recombination is normally suppressed by the activity of DNA pol theta-mediated end joining [34].…”