{"doi":"10.1002/pro.5117","title":"The <scp>U1</scp>‐<scp>70K</scp> and <scp>SRSF1</scp> interaction is modulated by phosphorylation during the early stages of spliceosome assembly","abstract":"In eukaryotes, pre-mRNA splicing is vital for RNA processing and orchestrated by the spliceosome, whose assembly starts with the interaction between U1-70K and SR proteins. Despite the significance of the U1-70K/SR interaction, the dynamic nature of the complex and the challenges in obtaining soluble U1-70K have impeded a comprehensive understanding of the interaction at the structural level for decades. We overcome the U1-70K solubility issues, enabling us to characterize the interaction between U1-70K and SRSF1, a representative SR protein. We unveil specific interactions: phosphorylated SRSF1 RS with U1-70K BAD1, and SRSF1 RRM1 with U1-70K RRM. The RS/BAD1 interaction plays a dominant role, whereas the interaction between the RRM domains further enhances the stability of the U1-70K/SRSF1 complex. The RRM interaction involves the C-terminal extension of U1-70K RRM and the conserved acid patches on SRSF1 RRM1 that is involved in SRSF1 phase separation. Our circular dichroism spectra reveal that BAD1 adapts an α-helical conformation and RS is intrinsically disordered. Intriguingly, BAD1 undergoes a conformation switch from α-helix to β-strand and random coil upon RS binding. In addition to the regulatory mechanism via SRSF1 phosphorylation, the U1-70K/SRSF1 interaction is also regulated by U1-70K BAD1 phosphorylation. We find that U1-70K phosphorylation inhibits the U1-70K and SRSF1 interaction. Our structural findings are validated through in vitro splicing assays and in-cell saturated domain scanning using the CRISPR method, providing new insights into the intricate regulatory mechanisms of pre-mRNA splicing.","journal":"Protein Science","year":2024,"id":440786,"datarank":0.0,"base_score":0.0,"endowment":0.0,"self_citation_contribution":0.0,"citation_network_contribution":0.0,"self_endowment_contribution":0.0,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":9,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9496,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2024-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":1252741,"name":"Pengcheng Zhang","orcid":"0000-0001-8749-5250","position":1,"is_corresponding":false},{"id":1010665,"name":"Zihan Zhang","orcid":"0000-0003-1362-4229","position":2,"is_corresponding":false},{"id":1010663,"name":"Talia Fargason","orcid":"0000-0001-6888-0356","position":3,"is_corresponding":false},{"id":1010664,"name":"Naiduwadura Ivon Upekala De Silva","orcid":"0000-0002-5937-0271","position":4,"is_corresponding":false},{"id":1065081,"name":"Erin Powell","orcid":null,"position":5,"is_corresponding":false},{"id":1253239,"name":"Ethan Ekpenyong","orcid":null,"position":6,"is_corresponding":false},{"id":1253240,"name":"Shariq Jamal","orcid":null,"position":7,"is_corresponding":false},{"id":11782,"name":"Yanbao Yu","orcid":"0000-0003-2994-1974","position":8,"is_corresponding":false},{"id":121640,"name":"Peter E. Prevelige","orcid":null,"position":9,"is_corresponding":false},{"id":606898,"name":"Rui Lu","orcid":"0000-0003-1593-2612","position":10,"is_corresponding":false},{"id":519641,"name":"Jun Zhang","orcid":"0000-0002-5842-7424","position":11,"is_corresponding":false},{"id":1253238,"name":"Trent Paul","orcid":null,"position":0,"is_corresponding":true}],"reference_count":50,"raw_metadata":null,"created_at":"2026-07-19T02:01:01.842286Z","pmid":"39023093","pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}