| 2018 |
SHLD1 (C20orf196) is a core subunit of the shieldin complex (SHLD1-SHLD2-SHLD3-REV7), which localizes to DNA double-strand break sites in a 53BP1- and RIF1-dependent manner to protect DNA ends and promote non-homologous end joining (NHEJ). Loss of SHLD1 impairs NHEJ, leads to defective immunoglobulin class switching, causes hyper-resection, and restores homologous recombination in BRCA1-deficient cells, conferring PARP inhibitor resistance. |
CRISPR screens, Co-IP, epistasis analysis, cellular DNA repair assays, immunofluorescence localization |
Nature |
High |
30022119 30022158 30022168 30046110
|
| 2018 |
SHLD1 (C20orf196) forms a complex with FAM35A (SHLD2) and REV7, and this complex is recruited to DSBs downstream of RIF1 in vivo. The complex prevents DNA end resection in BRCA1-mutant cells. FAM35A preferentially binds single-strand DNA (ssDNA) in vitro, consistent with a direct DNA-end protection mechanism. |
Mass spectrometry-based interactome, Co-IP, in vitro ssDNA binding assay, epistasis analysis, live-cell localization |
Nature communications |
High |
30154076 30254264
|
| 2018 |
Shieldin (including SHLD1) acts downstream of 53BP1-RIF1 and recruits the CST complex, which in turn recruits Polymerase-α (Polα)-primase to DSB sites to perform fill-in synthesis, thereby limiting single-stranded DNA at DSBs and counteracting resection. |
Co-IP of CST with shieldin, immunofluorescence co-localization of Polα at DSBs, depletion epistasis, BrdU incorporation at DSBs |
Nature |
High |
30022158 35027730
|
| 2020 |
Crystal structure of the SHLD3-REV7-SHLD2 ternary complex revealed that shieldin assembly requires an unexpected conformational dimer of REV7 in closed (C-REV7) and open (O-REV7) states mediated by SHLD3, with SHLD2 interacting with O-REV7. The conserved FXPWFP motif of SHLD3 binds to C-REV7 and blocks REV1 binding, thereby excluding shieldin from the REV1/Pol-ζ translesion synthesis complex. Disruption of the REV7 conformational dimer abolishes shieldin assembly and impairs NHEJ. |
Crystal structure determination, mutagenesis, NHEJ efficiency assays |
Nature communications |
High |
32332881 33597306
|
| 2021 |
Cryo-EM structures of the SHLD2-SHLD3-REV7-TRIP13 complex revealed that the N-terminus of REV7 inserts into the central channel of the TRIP13 hexamer, and ATP hydrolysis-triggered rotatory motions of TRIP13 pull the C-REV7 safety-belt segment through the channel, causing conformational disassembly of the shieldin complex. This TRIP13-mediated remodeling of shieldin promotes homology-directed repair at the expense of NHEJ. |
Cryo-EM structure, crystal structure of SHLD3-REV7 binary complex, in vitro disassembly assays |
Proceedings of the National Academy of Sciences of the United States of America |
High |
31915374 33597306
|
| 2020 |
TRIP13 ATPase catalyzes the transition of REV7 from an active 'closed' conformation to an inactive 'open' conformation, thereby dissociating the REV7-shieldin (including SHLD1-3) complex to promote homologous recombination and confer PARP inhibitor resistance. |
Biochemical conformation assays, Co-IP, loss-of-function and overexpression experiments, DNA repair pathway choice assays |
Nature cell biology |
High |
31915374 34521823
|
| 2021 |
MAD2L2 (REV7) dimerization within shieldin is mediated by SHLD2 and is required for MAD2L2-SHLD3 interaction and proper shieldin complex assembly. Dimerization-defective MAD2L2 impairs shieldin assembly and fails to promote NHEJ. MAD2L2 dimerization together with SHLD3 enables shieldin to interact with the TRIP13 ATPase. |
Co-IP, mutagenesis of MAD2L2 dimerization surface, NHEJ functional assays, CSR assays |
Nature communications |
Medium |
34521823
|
| 2022 |
In BRCA1-deficient cells, SHLD1 acts primarily by recruiting CST to DSBs, as CST tethered near DSBs bypassed the requirement for shieldin; a SHLD1 mutant defective in CST binding (SHLD1Δ) was non-functional in BRCA1-deficient cells. However, SHLD1Δ was fully functional at dysfunctional telomeres and during class switch recombination, where CST can be recruited independently of SHLD1. |
Mutagenesis of SHLD1 CST-binding domain, artificial tethering of CST to DSBs, functional rescue assays in BRCA1-deficient cells, CSR assays |
Nature cell biology |
High |
35027730
|
| 2022 |
SHLD1 is dispensable for lymphocyte development and RAG-mediated V(D)J recombination (even in XLF-deficient cells), but is essential for restricting resection at AID-induced DSB ends during class switch recombination in both NHEJ-proficient and NHEJ-deficient B cells, and is required for orientation-specific joining of AID-initiated DSBs. |
SHLD1 knockout mice, B cell CSR assays, V(D)J recombination assays, resection quantification |
Nature communications |
Medium |
35764636
|
| 2021 |
The transcription factors THAP1, YY1, and HCF1 bind directly to the SHLD1 promoter and cooperatively maintain the low basal expression of SHLD1, thereby controlling the balance between end protection and resection. Loss of THAP1-dependent SHLD1 expression confers PARP inhibitor and cisplatin cross-resistance in BRCA1-deficient cells. Ablation of SHLD1 rescues embryonic lethality and PARPi sensitivity of BRCA1-deficient mice. |
Chromatin immunoprecipitation, promoter reporter assays, knockout mouse models, PARP inhibitor sensitivity assays |
Molecular cell |
Medium |
33857404
|
| 2025 |
CTC1 (of CST) and SHLD1 are epistatic in preventing exacerbated DNA end resection and genetic instability during class switch recombination. Notably, a SHLD1 mutant defective in CST binding via the LDLP motif (SHLD1ΔLDLP) is fully proficient for CSR, demonstrating that the direct SHLD1-CTC1 interaction through this specific motif is dispensable for CST and SHLD functions in promoting productive CSR. |
CRISPR knockout of CTC1 and SHLD1 in AID-inducible B cell lines, complementation with SHLD1ΔLDLP mutant, CSR assays, resection quantification |
European journal of immunology |
Medium |
40178294
|
| 2025 |
In the absence of NHEJ (XRCC4 deficiency) or DSB end protection (SHLD1 deficiency) during class switch recombination, Polymerase theta (Pol θ) mediates an alternative end-joining pathway characterized by end resection, inversion, and microhomology usage. This Pol θ-mediated repair occurs at the G1-to-S phase transition and is independent of RHINO and PLK1. |
Knockout of XRCC4, SHLD1, and/or Pol θ in primary B cells, CSR assays, sequencing of switch junctions |
Nature communications |
Medium |
41298353
|