The spliceosome associated protein of ~49 kDa (SAP49), also known as SF3B4, is a widely expressed nuclear splicing factor that has been shown to have RNA binding activity as well as direct interaction with SAP145 (Champion-Arnaud and Reed 1994). The SAP145-SAP49 complex has recently been implicated in cell cycle progression as Vpr (viral protein 1 of HIV-1) has been shown to bind SAP145 thus interfering with the proper formation and functioning of the SAP145-SAP49 complex (Terada and Yasuda 2006).
