| Modification Notes |
SAP 114 (spliceosome associated protein 114), also known as PRP21, PRPF21, SF3A120 or SF3A1, is a 793 amino acid ubiquitously expressed nuclear protein belonging to the SURP protein family and contains two SURP motif repeats and one ubiquitin-like domain. SAP 114 is a subunit of the SF3A splicing factor, a heterotrimeric complex comprised of three subunits that act in tandem to mediate the binding of U2 snRNP to the branchpoint sequence (BPS) in pre-mRNA. The SF3A complex is necessary for the conversion of 15S U2 snRNP into the active 17S protein that performs directly in pre-mRNA splicing events. Functioning as the first subunit of the complex, SAP 114 interacts with subunit 2 (SAP 62) and subunit 3 (SAP 61) via its SURP motifs. SAP 114 is also thought to be involved in the assembly of the E complex, a critical regulator of cell cycle progression from G1 into S phase in mammalian cells. |