ZFP207 interacts with U1 snRNP to promote spliceosome assembly via phase separation [ZFP207_CLIP]

U1 snRNP plays an essential role in initiating spliceosome assembly, yet the mechanism underlying its synergy with other splicing regulators for efficient spliceosome assembly remains elusive. Here we identify ZFP207 as a key regulator of U1 snRNP function that substantially promotes spliceosome assembly. Acute depletion of ZFP207 recapitulates the molecular phenotypes observed with the depletion of SNRNP70, a core component of U1 snRNP. Mechanistically, the N-terminal zinc finger domains of ZFP207 directly bind to U1 snRNA, while its C-terminus undergoes phase separation via intrinsically disordered regions (IDRs). The coordination between the N-terminus and C-terminus of ZFP207 drives the formation of biomolecular condensate with U1 snRNP, which creates a molecular environment to promote spliceosome assembly by facilitating the interactions between U1 snRNP and other splicing regulators. Collectively, our study demonstrates the critical role of ZFP207-mediated phase separation in ensuring proper U1 snRNP function and spliceosome assembly. We did the CLIPFB-seq to identify the binding sites of ZFP207. Peak calling using data obtained from CLIPFB-seq of each replicate in control and ZFP207AID group. Comparative peak and motif analysis of CLIPFB-seq data of control and ZFP207AID group.