High Quality Content by WIKIPEDIA articles! ASF/SF2 (alternative splicing factor/splicing factor 2) also known as splicing factor, arginine/serine-rich 1 or SFRS1, is a protein which in humans is encoded by the SFRS1 gene. ASF/SF2 is an essential sequence specific splicing factor involved in pre-mRNA splicing. SFRS1 is the gene that codes for ASF/SF2 and is found on chromosome 17. The resulting splicing factor is a protein of approximately 33 kDa. ASF/SF2 is necessary for all splicing reactions to occur, and influences splice site selection in a concentration-dependent manner, resulting in alternative splicing. In addition to being involved in the splicing process, ASF/SF2 also mediates post-splicing activities, such as mRNA nuclear export and translation.