ZMAT5

ZMAT5 is a structural subunit of the 13-protein human U11 snRNP, a core component of the minor (U12-dependent) spliceosome. Cryo-EM structures of the U11 snRNP in apo and substrate-bound states show that ZMAT5 is positioned near the 5′ end of U11 snRNA, where it stabilizes the binding of incoming U12-type 5′ splice sites during pre-mRNA recognition (PMID:39809272).

1. 2025 High

   The structural basis by which the minor spliceosome recognizes U12-type 5′ splice sites was unknown; cryo-EM of the human U11 snRNP revealed that ZMAT5 sits near the 5′ end of U11 snRNA and directly stabilizes 5′SS binding, establishing its mechanistic role in minor intron recognition.

   Evidence Cryo-EM reconstruction of human U11 snRNP in apo and substrate-bound conformations

   PMID:39809272

   Open questions at the time

   • No loss-of-function or mutagenesis data defining which ZMAT5 residues are essential for 5′SS stabilization
   • Contribution of ZMAT5 to minor spliceosome activity in vivo (e.g., splicing efficiency of U12-type introns) has not been tested
   • Whether ZMAT5 participates in later spliceosomal complexes beyond U11 snRNP is unresolved

• The functional consequences of ZMAT5 depletion or mutation on minor intron splicing and cell physiology remain uncharacterized.
• No knockdown/knockout phenotype reported
• No disease association established through direct genetic evidence
• No biochemical reconstitution of ZMAT5's contribution to splice-site duplex stability