Cell cycle progression is controlled in part by a family of cyclin proteins and cyclin dependent kinases (Cdks). Cdk proteins work in concert with the cyclins to phosphorylate key substrates involved in each phase of cell cycle progression. Another family of proteins, Cdk inhibitors, also plays a role in regulating the cell cycle by binding to cyclin-Cdk complexes and modulating their activity. Cdks are considered potential targets for anti-cancer therapy due to their involvement with cell cycle regulation. Cdks are also involved in the regulation of transcription and mRNA processing. CdkL4 (cyclin-dependent kinase-like 4) is a 315 amino acid protein that belongs to the CMGC Ser/Thr protein kinase family and may be involved in cell cycle regulation.