Small Nuclear RNA Activating Complex Polypeptide 4 (SNAPC4)

SNAPC4 (SNAP190), the largest known subunit of the SNAP complex (190 kD), by a combination of library screens and direct RT-PCR. The 1,469-amino acid protein encoded by this sequence contains a Myb protein domain followed by arginine- and serine-rich regions, and a carboxy-terminal region with a leucine zipper-like motif. SNAPC4 is required for both RNA polymerase II and III transcription of snRNA genes and that it interacts strongly with SNAPC2 but not with SNAPC1 or SNAPC3. In addition, they found that whereas full-length SNAPC4 protein did not bind to the PSE, a truncated protein containing the Rc and Rd repeats within the Myb domain was able to bind DNA specifically. The carboxy-terminal half of SNAPC4 can interact with DNA-bound transcription activator Oct-1.