Involved in pre-mRNA splicing. Found in nuclear intrachromatin granules clusters (IGC), also called nuclear speckles, which are storage compartments for nuclear proteins involved in mRNA processing. Contains a RS region (arginine-serine dipeptide repeat) within the C-terminal domain which is the hallmark of the SR family of splicing factors. This region probably plays a role in protein-protein interactions (By similarity). Belongs to the cyclin family. Cyclin L subfamily.