SC35, a member of the SR protein family, is an essential pre-mRNA splicing factor and can function as an essential splicing factor as well as an alternative splicing factor. Phosphorylation of serine residues located within the SR domain directly regulates SC35 activity and compartmentalization of other SR splicing factors. In addition to interacting with RNA and other splicing factors, SC35 has been shown to interact either directly or indirectly with the C-terminal domain (CTD) of the largest subunit of RNA polymerase II, thereby suggesting a potential role of SC35 in coordinating transcription and pre-mRNA splicing.
