Plays a role in pre-mRNA splicing as component of the U4/U6- U5 tri-snRNP complex that is involved in spliceosome assembly, and as component of the precatalytic spliceosome (spliceosome B complex) (PubMed:28781166). The heptameric LSM2-8 complex binds specifically to the 3'-terminal U-tract of U6 snRNA (PubMed:10523320). . This is the function of LSM8 (LSM8 homolog, U6 small nuclear RNA associated, ENSG00000128534).