CDC2-like kinase 5 (CDC2L5) is a member of the cyclin-dependent serine/threonine protein kinase family that plays a central role in cell cycle control. The CDC2L5 cDNA was first identified as CHED (cholinesterase-related cell-division controller) and cloned serendipitously in a screen using a cholinesterase-specific oligonucleotide probe in search of a link between cholinergic signaling and hematopoietic cell division control. Recently, the understanding of the physiological function of CDC2L5 has become clearer. Due to its localization to speckles in the nucleoplasm and its interaction with the splicing protein, ASF/SF2-associated protein p32, it was suggested to play a role in mRNA processing. Further studies showed that overexpression of CDC2L5 altered mRNA splicing patterns, and that CDC2L5 associated with L-type cyclins known to be involved in alternative splicing. These results have led to the conclusion that CDC2L5 is part of a subfamily of cyclin dependent kinases that play a role in the regulation of alternative splicing.