Involved in pre-mRNA splicing and cell cycle progression. Required for the spliceosome assembly by promoting the functional integration of the U4/U6.U5 tri-snRNP particle into the U1-, U2-dependent pre-spliceosome. Also recruits PRP19 to the spliceosome, as a component of the NTC complex (or PRP19-associated complex). The association of the NTC complex to the spliceosome mediates conformational rearrangement or stabilizes the structure of the spliceosome after U4 snRNA dissociation, which leads to spliceosome maturation. Required for initiation of the DNA replication by binding the RNA replication origins, probably through its interaction with the origin recognition complex (ORC). Belongs to the NTC complex (or PRP19-associated complex), composed of at least CEF1, CLF1, ISY1, NTC20, SNT309, SYF1, SYF2, and PRP19. The NTC complex associates with the spliceosome after the release of the U1 and U4 snRNAs and forms the CWC spliceosome subcomplex (or CEF1-associated complex) reminiscent of a late-stage spliceosome composed also of the U2, U5 and U6 snRNAs and at least BUD13, BUD31, BRR2, CDC40, CUS1, CWC2, CWC15, CWC21, CWC22, CWC23, CWC24, CWC25, CWC27, ECM2, HSH155, IST3, LEA1, MSL1, PRP8, PRP9, PRP11, PRP21, PRP22, PRP45, PRP46, SLU7, SMB1, SMD1, SMD2, SMD3, SMX2, SMX3, SNU114, SPP2, RSE1 and YJU2. Interacts with CEF1, ISY1, MUD2, NTC20, PRP22, PRP40, PRP46, SYF1, SYF2, and the ORC2 subunit of the origin recognition complex. Present with 2140 molecules/cell in log phase SD medium. Belongs to the crooked-neck family.