Phospho-SF3B1 (Thr313) (D8D8V) Rabbit mAb #25009

Splicing factor 3b subunit 1 (SF3B1) is an integral component of the U2 small nuclear ribonucleoprotein (U2 snRNP) and plays an important role in the splicing of pre-mRNA that involves the removal of introns and the joining of exons to form mature mRNA (1-3). The assembly and proper recognition of splice sites are driven by sequences at the pre-mRNA intron-exon splice sites. The 5’ splice donor site is recognized by the U1 snRNP complex, while U2 snRNP binds to the 3’ splice site (branch point), ensuring the anchoring of the spliceosome machinery at the splice sites (3,4). Recent whole exome sequencing studies have demonstrated a high incidence of somatic mutations of SF3B1 in patients with various hematological malignancies such as chronic lymphocytic leukemia and myelodysplastic syndromes (2,3,5,6). Misregulation of pre-mRNA splicing arising from mutations of the spliceosome components such as SF3B1 is thought to contribute to changes in the expression patterns of key proteins that are involved in pathways such as cell cycle progression, cell death, and cancer metabolism (2,3).
Phosphorylation of SF3B1 at Thr313 is only found in catalytically active spliceosomes and associates mainly with chromatin, where about 80% of pre-mRNA splicing occurs. Treatment with a transcription inhibitor 5,6-dichloro-1-β-d-ribofuranosylbenzimidazole (DRB) leads to a decreased supply of pre-mRNA, resulting in the loss of phospho-SF3B1 (Thr313), consistent with its association with active splicing (7).