Loss of ZBTB24 impairs nonhomologous end-joining and class-switch recombination in patients with ICF syndrome
Angela Helfricht, Peter Thijssen, Magdalena B. Rother, Rashmi G. Shah, Likun Du, Sanami Takada, Mélanie Rogier, Jacques Moritz, Hanna IJspeert, Chantal Stoepker, Monique M. van Ostaijen-ten Dam, Vincent Heyer, Martijn S. Luijsterburg, Anton de Groot, Rianca Jak, Gwendolynn Grootaers, Jun Wang, Pooja Rao, Alfred C.O. Vertegaal, Maarten J. D. van Tol, Qiang Pan‐Hammarström, Bernardo Reina‐San‐Martin, Girish M. Shah, Mirjam van der Burg, Silvère M. van der Maarel, Haico van Attikum
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.