Involved in pre-mRNA splicing. Facilitates the cooperative formation of U2/U6 helix II in association with stem II in the spliceosome. Binds to RNA. Belongs to the CWC complex (or CEF1-associated complex), a spliceosome subcomplex composed of the U2, U5 and U6 snRNAs and at least BUD13, BUD31, BRR2, CDC40, CEF1, CLF1, CUS1, CWC2, CWC15, CWC21, CWC22, CWC23, CWC24, CWC25, CWC27, ECM2, HSH155, IST3, ISY1, LEA1, MSL1, NTC20, PRP8, PRP9, PRP11, PRP19, PRP21, PRP22, PRP45, PRP46, SLU7, SMB1, SMD1, SMD2, SMD3, SMX2, SMX3, SNT309, SNU114, SPP2, SYF1, SYF2, RSE1 and YJU2. Interacts with SLU7. Present with 4260 molecules/cell in log phase SD medium. Belongs to the SLT11 family.