SHLD1 is dispensable for 53BP1-dependent V(D)J recombination but critical for productive class switch recombination
Ontology highlight
ABSTRACT:
PROVIDER: PRJNA836576 | ENA |
REPOSITORIES: ENA
Dataset's files
| Action | DRS | |||
|---|---|---|---|---|
| SRR19146729_1.fastq.gz | Fastqsanger.gz | |||
| SRR19146729_2.fastq.gz | Fastqsanger.gz | |||
| SRR19146730_1.fastq.gz | Fastqsanger.gz | |||
| SRR19146730_2.fastq.gz | Fastqsanger.gz | |||
| SRR19146731_1.fastq.gz | Fastqsanger.gz |
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Project description:The shieldin (SHLD) complex, composed of SHLD1, SHLD2, SHLD3 and MAD2L2/REV7, acts downstream of 53BP1 to counteract DNA double-strand break (DSB) end-resection and promote non-homologous end-joining (NHEJ). While 53BP1 is essential for immunoglobulin heavy chain class switch recombination (CSR), long-range V(D)J recombination and for repair of RAG-induced DSBs in XLF-deficient cells, the role of SHLD in these activities remains elusive. Here, we report that contrary to 53BP1, SHLD1 is dispensable for lymphocyte development and V(D)J recombination, even in the sensitized XLF-deficient background or for the joining of distant V(D)J segments. By contrast, SHLD1 restricts resection at AID-induced DSB ends in both NHEJ-proficient and NHEJ-deficient B cells, providing an end-protection mechanism that permits productive CSR. Finally, we show that this end-protection function is required for orientation-specific joining of AID-initiated DSBs. We propose that 53BP1 promotes V(D)J recombination and CSR through two distinct mechanisms; the synapsis of V(D)J segments and switch regions within chromatin independently of SHLD and the protection of AID-DSB ends against resection mediated by SHLD.
2022-05-11 | GSE202567 | GEO
Project description:53BP1 governs a specialized, context-specific branch of the classical non-homologous end joining DNA double-strand break repair pathway. Mice lacking 53bp1 (also known as Trp53bp1) are immunodeficient owing to a complete loss of immunoglobulin class-switch recombination, and reduced fidelity of long-range V(D)J recombination. The 53BP1-dependent pathway is also responsible for pathological joining events at dysfunctional telomeres, and its unrestricted activity in Brca1-deficient cellular and tumour models causes genomic instability and oncogenesis. Cells that lack core non-homologous end joining proteins are profoundly radiosensitive, unlike 53BP1-deficient cells, which suggests that 53BP1 and its co-factors act on specific DNA substrates. Here we show that 53BP1 cooperates with its downstream effector protein REV7 to promote non-homologous end joining during class-switch recombination, but REV7 is not required for 53BP1-dependent V(D)J recombination. We identify shieldin—a four-subunit putative single-stranded DNA-binding complex comprising REV7, c20orf196 (SHLD1), FAM35A (SHLD2) and FLJ26957 (SHLD3)— as the factor that explains this specificity. Shieldin is essential for REV7-dependent DNA end-protection and non-homologous end joining during class-switch recombination, and supports toxic non-homologous end joining in Brca1-deficient cells, yet is dispensable for REV7-dependent interstrand cross-link repair. The 53BP1 pathway therefore comprises distinct double-strand break repair activities within chromatin and single-stranded DNA compartments, which explains both the immunological differences between 53bp1- and Rev7- deficient mice and the context specificity of the pathway.
2018-07-26 | PXD009650 | Pride
Project description:RAG endonuclease initiates V(D)J recombination by cleaving recombination signal sequences (RSSs), subsequently repaired by classical nonhomologous end-joining (c-NHEJ). However, 53BP1, as a key DNA damage response (DDR) factor promoting c-NHEJ, is dispensable for V(D)J recombination. Here, we report that 53BP1 orchestrates sequence strength of RAG targets to shape end-joining features during V(D)J recombination. Deficiency of 53BP1, rather than other DDR factors, specifically increases junctional microhomology (MH) of cryptic RSS (cRSS) recombination instead of RSS recombination. Depletion of RIF1 or Shieldin, downstream factors of 53BP1, partially mimics the phenotypes of 53BP1-deficiency. Notably, loss of RNF168, rather than other classical resection and alternative end-joining factors, is sufficient to fully rescue 53BP1-deficiency-mediated increase of junctional MH during cRSS recombination. Remarkably, RAG mutant and RSS score analyses indicate that sequence strength of RAG targets determines the unique roles of 53BP1 in balancing end-joining outcomes. Our findings provide deeper mechanistic insights into DNA damage repair for RAG cleaved on- and off-targets during V(D)J recombination.
2026-04-09 | GSE270090 | GEO
Project description:RAG endonuclease initiates V(D)J recombination by cleaving recombination signal sequences (RSSs), subsequently repaired by classical nonhomologous end-joining (c-NHEJ). However, 53BP1, as a key DNA damage response (DDR) factor promoting c-NHEJ, is dispensable for V(D)J recombination. Here, we report that 53BP1 orchestrates sequence strength of RAG targets to shape end-joining features during V(D)J recombination. Deficiency of 53BP1, rather than other DDR factors, specifically increases junctional microhomology (MH) of cryptic RSS (cRSS) recombination instead of RSS recombination. Depletion of RIF1 or Shieldin, downstream factors of 53BP1, partially mimics the phenotypes of 53BP1-deficiency. Notably, loss of RNF168, rather than other classical resection and alternative end-joining factors, is sufficient to fully rescue 53BP1-deficiency-mediated increase of junctional MH during cRSS recombination. Remarkably, RAG mutant and RSS score analyses indicate that sequence strength of RAG targets determines the unique roles of 53BP1 in balancing end-joining outcomes. Our findings provide deeper mechanistic insights into DNA damage repair for RAG cleaved on- and off-targets during V(D)J recombination.
2026-04-09 | GSE270088 | GEO
Project description:RAG endonuclease initiates V(D)J recombination by cleaving recombination signal sequences (RSSs), subsequently repaired by classical nonhomologous end-joining (c-NHEJ). However, 53BP1, as a key DNA damage response (DDR) factor promoting c-NHEJ, is dispensable for V(D)J recombination. Here, we report that 53BP1 orchestrates sequence strength of RAG targets to shape end-joining features during V(D)J recombination. Deficiency of 53BP1, rather than other DDR factors, specifically increases junctional microhomology (MH) of cryptic RSS (cRSS) recombination instead of RSS recombination. Depletion of RIF1 or Shieldin, downstream factors of 53BP1, partially mimics the phenotypes of 53BP1-deficiency. Notably, loss of RNF168, rather than other classical resection and alternative end-joining factors, is sufficient to fully rescue 53BP1-deficiency-mediated increase of junctional MH during cRSS recombination. Remarkably, RAG mutant and RSS score analyses indicate that sequence strength of RAG targets determines the unique roles of 53BP1 in balancing end-joining outcomes. Our findings provide deeper mechanistic insights into DNA damage repair for RAG cleaved on- and off-targets during V(D)J recombination.
2026-04-09 | GSE270086 | GEO
Project description:RAG endonuclease initiates V(D)J recombination by cleaving recombination signal sequences (RSSs), subsequently repaired by classical nonhomologous end-joining (c-NHEJ). However, 53BP1, as a key DNA damage response (DDR) factor promoting c-NHEJ, is dispensable for V(D)J recombination. Here, we report that 53BP1 orchestrates sequence strength of RAG targets to shape end-joining features during V(D)J recombination. Deficiency of 53BP1, rather than other DDR factors, specifically increases junctional microhomology (MH) of cryptic RSS (cRSS) recombination instead of RSS recombination. Depletion of RIF1 or Shieldin, downstream factors of 53BP1, partially mimics the phenotypes of 53BP1-deficiency. Notably, loss of RNF168, rather than other classical resection and alternative end-joining factors, is sufficient to fully rescue 53BP1-deficiency-mediated increase of junctional MH during cRSS recombination. Remarkably, RAG mutant and RSS score analyses indicate that sequence strength of RAG targets determines the unique roles of 53BP1 in balancing end-joining outcomes. Our findings provide deeper mechanistic insights into DNA damage repair for RAG cleaved on- and off-targets during V(D)J recombination.
2026-04-09 | GSE270092 | GEO
Project description:RAG endonuclease initiates immunoglobulin heavy chain (Igh) V(D)J recombination by cleaving V, D and J gene segments flanked by recombination signal sequences (RSSs), subsequently joined exclusively by classical nonhomologous end joining (c-NHEJ). While 53BP1, a key DNA damage response (DDR) factor promoting c-NHEJ, was reported to be dispensable for Igh V(D)J recombination. Here, we report that 53BP1 is a unique DDR factor playing unrecognized roles in joining RAG-initiated DNA breaks. Both RAG-cleaved RSSs and cryptic RSSs (cRSSs) are joined by c-NHEJ. Deficiency of 53BP1, rather than other DDR factors, slightly decreased the proximal V(D)J recombination without affecting c-NHEJ of RAG-initiated RSS breaks, but significantly increased microhomology (MH)-mediated alternative end joining (A-EJ) of RAG-initiated cRSS breaks, indicating that 53BP1 is specifically required for c-NHEJ of RAG-initiated cRSS breaks. Thus, our findings provide new insights into the distinct roles of 53BP1 in joining RAG-cleaved on- and off-targets during exclusively c-NHEJ-mediated V(D)J recombination
2026-04-09 | GSE270087 | GEO
Project description: Not available
| S-EPMC9240092 | biostudies-literature
Project description:53BP1 activity drives genome instability and embryonic lethality in BRCA1-deficient cells by inhibiting homologous recombination (HR).53BP1’s anti-recombinogenic functions require phosphorylation-dependent interactions with two effector complexes, PTIP and RIF1/Shieldin. While RIF1/Shieldin is thought to block 5’-3’ nucleolytic processing of DNA ends, it remains unclear how PTIP antagonizes HR. Here we show that mutation of the PTIP interaction site in 53BP1 (S25A) increases Shieldin association with DNA damage. Despite excessive Shieldin “end-blocking” activity, the mutant protein allows end resection sufficient to rescue the lethality of BRCA1D11 mice. End resection in BRCA1D1153BP1S25A mice is rewired in a manner driven by DNA2 since Shieldin blocks EXO1-mediated nucleolytic processing. Despite ample resection, mutant cells fail to complete HR, as 53BP1/Shieldin also inhibits RNF168-mediated loading of PALB2/RAD51 onto ssDNA post-resection. As a result, BRCA1D1153BP1S25A mice exhibit hallmark features of HR insufficiency, including increased developmental neuronal apoptosis, premature aging and hypersensitivity to PARP inhibitors. Disruption of Shieldin or forced targeting of PALB2 to ssDNA in BRCA1D1153BP1S25A cells restores RNF168 recruitment, RAD51 nucleofilament formation, and PARPi resistance. Our study supports a model in which RIF1/Shieldin and PTIP associate independently with 53BP1 to regulate distinct end-resection pathways, and reveals a critical function of 53BP1/Shieldin post-resection that limits RNF168-mediated loading of RAD51.
2019-10-22 | GSE133806 | GEO