9nh5
CRYO-EM STRUCTURE OF HUMAN U7 SNRNP WITH METHYLATED noncleavable H2A* SUBSTRATE PRE-MRNA (core region)
Structural highlights
FunctionSMD3_HUMAN Appears to function in the U7 snRNP complex that is involved in histone 3'-end processing. Binds to the downstream cleavage product (DCP) of histone pre-mRNA in a U7 snRNP dependent manner.[1] Publication Abstract from PubMedThe U7 snRNP (small nuclear ribonucleoprotein) is responsible for the 3'-end processing of replication-dependent histone messenger RNA precursors (pre-mRNAs). A helix in the Lsm11 N-terminal extension contacts the metallo-beta-lactamase domain of the U7 snRNP endonuclease CPSF73. We mutated or deleted this helix and found that the mutant machineries had substantially reduced cleavage activity toward the pre-mRNA. Our cryo-electron microscopy (cryo-EM) studies indicated that the helix was important for helping to hold CPSF73 in its correct position for the cleavage reaction. We also reconstituted a wild-type U7 snRNP in complex with a methylated, noncleavable pre-mRNA. We observed that CPSF73 could achieve an open conformation independent of RNA binding to its active site. Finally, we found that a previously uninterpreted EM density for a small helix at the CPSF73-CPSF100 interface belonged to the C-terminal end of CstF77, copurified from insect cells and highly conserved among CstF77 homologs. This CstF77 binding site had a small effect on the cleavage activity of U7 snRNP. Overall, our studies have revealed the importance of the conserved helix in the Lsm11 N-terminal extension for U7 snRNP, provided structural evidence that CPSF73 can achieve an open, active conformation without RNA binding in its active site, and identified a previously unknown binding site for CstF77 in CPSF100. An N-terminal helix of Lsm11 stabilizes CPSF73 in U7 snRNP for histone pre-mRNA 3'-end processing.,Desotell A, Marzluff WF, Dominski Z, Tong L Nucleic Acids Res. 2026 Jan 5;54(1):gkaf1442. doi: 10.1093/nar/gkaf1442. PMID:41495886[2] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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