MED12L is a gene that plays a crucial role in transcriptional coactivation of nearly all RNA polymerase II-dependent genes. It is highly conserved across eukaryotes and contains 43 exons. The protein encoded by MED12L is a component of the Mediator complex, which is involved in linking gene-specific transcription activators with the basal transcription machinery. The Mediator complex is composed of 30 subunits organized into four modules: Kinase, Head, Middle, and Tail. MED12L is predicted to be a subunit of the kinase module, along with MED12, MED13, MED13L, CDK8, CDK19, and Cyclin C.