Loss of ZBTB24 impairs nonhomologous end-joining and class-switch recombination in patients with ICF syndrome

Abstract

The autosomal recessive immunodeficiency, centromeric instability, and facial anomalies (ICF) syndrome is a genetically heterogeneous disorder. Despite the identification of the underlying gene defects, it is unclear how mutations in any of the four known ICF genes cause a primary immunodeficiency. Here we demonstrate that loss of ZBTB24 in B cells from mice and ICF2 patients affects nonhomologous end-joining (NHEJ) during immunoglobulin class-switch recombination and consequently impairs immunoglobulin production and isotype balance. Mechanistically, we found that ZBTB24 associates with poly(ADP-ribose) polymerase 1 (PARP1) and stimulates its auto-poly(ADP-ribosyl)ation. The zinc-finger in ZBTB24 binds PARP1-associated poly(ADP-ribose) chains and mediates the PARP1-dependent recruitment of ZBTB24 to DNA breaks. Moreover, through its association with poly(ADP-ribose) chains, ZBTB24 protects them from degradation by poly(ADP-ribose) glycohydrolase (PARG). This facilitates the poly(ADP-ribose)-dependent assembly of the LIG4/XRCC4 complex at DNA breaks, thereby promoting error-free NHEJ. Thus, we uncover ZBTB24 as a regulator of PARP1-dependent NHEJ and class-switch recombination, providing a molecular basis for the immunodeficiency in ICF2 syndrome.

Interplay between Histone and DNA Methylation Seen through Comparative Methylomes in Rare Mendelian Disorders

“…This aberrant activation of the innate immune system was suggested to explain autoimmunity that affects some of the ICF patients [ 64 ]. In addition, recent studies have highlighted a role for ZBTB24, CDCA7 and HELLS in Non-homologous end joining (NHEJ), a pathway involved in DNA repair but also in immunoglobulin class-switch recombination, linking LoF of ICF factors to immunodeficiency that affects most of ICF patients [ 41 , 65 ].…”

Chromatin remodeling in replication‐uncoupled maintenance DNA methylation and chromosome stability: Insights from ICF syndrome studies

“…We revealed that this complex facilitates the nonhomologous end joining (NHEJ) of double-strand breaks (DSBs) by enhancing access of Ku80 (also called XRCC5), a factor essential for NHEJ by protecting DSB ends from resection, to the sites of DSBs, and potentially suppresses many cytological defects; ZBTB24 KO, CDCA7 KO, and HELLS KO human embryonic kidney 293 (HEK293) cells generated using the CRISPR/ Cas9 system displayed enlarged nuclei, centrosome amplification, abnormal chromosome segregation, and many related phenotypes, including proliferation defects, aneuploidy, and apoptosis (Unoki et al, 2019). Recently, it was reported that ZBTB24 and HELLS are essential for NHEJ during immunoglobulin class-switch recombination (He et al, 2020;Helfricht et al, 2020). Taken together, these findings indicate that ZBTB24, CDCA7, and HELLS are largely involved in the same biological pathway, although they also have their specific functions; for example, (Jarvis et al, 1996) Genes to Cells UNOKI ZBTB24 works not only as a transcriptional activator of CDCA7, but also as a direct regulator of poly(ADP-ribose) polymerase 1 (PARP1)-dependent NHEJ and class-switch recombination (Helfricht et al, 2020).…”

“…Recently, it was reported that ZBTB24 and HELLS are essential for NHEJ during immunoglobulin class-switch recombination (He et al, 2020;Helfricht et al, 2020). Taken together, these findings indicate that ZBTB24, CDCA7, and HELLS are largely involved in the same biological pathway, although they also have their specific functions; for example, (Jarvis et al, 1996) Genes to Cells UNOKI ZBTB24 works not only as a transcriptional activator of CDCA7, but also as a direct regulator of poly(ADP-ribose) polymerase 1 (PARP1)-dependent NHEJ and class-switch recombination (Helfricht et al, 2020).…”

“…Our recent studies of ICF-related proteins have deepened our insights into the molecular mechanisms of maintenance DNA methylation and chromosome stability (Unoki et al, 2019(Unoki et al, , 2020. The recent studies showing that ZBTB24 and HELLS are involved in NHEJ during immunoglobulin class-switch recombination (He et al, 2020;Helfricht et al, 2020) have also deepened our insights into the molecular mechanisms of antibody production. Despite its rareness, studies of ICF syndrome have revealed many scientifically important propositions and are surely expected to provide additional insights regarding maintenance DNA methylation, chromosome stability, antibody production, morphogenesis of the face, and neurogenesis during development.…”

FLYWCH1, a Multi-Functional Zinc Finger Protein Contributes to the DNA Repair Pathway

“…In the past years, the roles of zinc finger domain-containing proteins in the DNA damage response and double-strand breaks (DSBs) repair have gained great attention [ 7 ]. Several proteins have emerged as key players in many cellular processes such as cell migration and DSB repair [ 8 , 9 , 10 ]. However, the C2H2 zinc finger domain is best known for its role in sequence-specific DNA-binding proteins as the zinc finger transcription factor or in protein–protein interaction involved in post-translation modification (including FLYWCH1) [ 6 , 11 , 12 , 13 ].…”