Members of this family are part of the SNAPc complex (SNAPC1) required for the transcription of both RNA polymerase II and III small-nuclear RNA genes. They bind to the proximal sequence element (PSE), a non-TATA-box basal promoter element common to these 2 types of genes. Furthermore, they also recruit TBP and BRF2 to the U6 snRNA TATA box.