Small Nuclear RNA Activating Complex Polypeptide 5 (SNAPC5)

The PSE binds a multisubunit complex, the snRNA-activating protein complex (SNAPC), that copurifies with the TATA box-binding protein (TBP).Sequence analysis predicted that the 98-amino acid protein contains a leucine zipper motif at its N terminus and a 10-residue glutamate stretch at its C terminus. Supershift and immunoblot analyses confirmed the existence of SNAPC5 in the complex with the PSE and that it is required for snRNA gene transcription by both pol II and pol III. Immunoprecipitation analysis of cotranslated SNAP genes suggested that SNAPC4 forms a backbone on which SNAPC2 and SNAPC5 assemble. The latter is essential for the subsequent assembly of SNAPC1 with SNAPC4, which is followed by the assembly of SNAPC3 with SNAPC1.