Serine/Arginine Rich Splicing Factor 12 (SRSF12)

The 40-kDa protein cannot complement SR protein-deficient HeLa cell S100 extract and showed a dominant negative effect in vitro against the authentic SR proteins, SF2/ASF and SC35. Interestingly, the 40- and 35-kDa proteins antagonize SR proteins and activate the most distal alternative 5' splice site of adenovirus E1A pre-mRNA in vivo, an activity that is similar to that characterized previously for the heterogeneous nuclear ribonucleoprotein particles A/B group of proteins. A series of recombinant chimeric proteins consisting of domains from these proteins and SC35 in various combinations showed that the RRM SRrp40 and SRrp35, respectively, for SR-repressor proteins of approximately 40 and approximately 35 kDa. Both factors show tissue- and cell type-specific patterns of expression.