Abstact

The subcortical maternal complex (SCMC) is essential for mammalian preimplantation development, yet how SCMC(core) (MATER/NLRP5, TLE6, FLOPED/OOEP) engages regulatory partners remains unclear. We determined cryo-EM structures of mouse SCMC bound to ZBED3 and human SCMC bound to NLRP2. Our structure reveals that ZBED3 interacts with all three SCMC(core) subunits via its zinc finger domain, with conserved residue Phe73 mediating specific contacts. In contrast, human NLRP2 only binds to the WD40 domain of TLE6 through its leucine-rich repeat (LRR) domain. Similar interactions were also confirmed for NLRP7 with TLE6. These findings were cross-validated by in vivo proximity ligation and in vitro pull-down assays. Our work proposes a paradigmatic "Lego-like" assembly model, where the SCMC(core) sequentially recruits different partners through diverse molecular interfaces. These findings provide critical structural insights into the SCMC's architecture and its multifaceted regulatory roles in early mammalian embryogenesis.