The Mediator complex is a large and essential protein complex that plays a central role in the general regulation of gene expression in eukaryotes. It acts as a bridge between transcription factors bound to transcriptional enhancer regions and RNA polymerase II (RNAPII) at the promoter, facilitating the initiation and regulation of transcription. The Mediator complex is highly conserved across eukaryotes and consists of multiple subunits. Whilst the composition and arrangement of subunits varies between species, a core set of subunits is present in most organisms. In humans, the Mediator complex consists of approximately 30 subunits, organized into four distinct modules: the Head, Middle, Tail, and Kinase modules, with each of these modules having specific functions in transcriptional regulation. The Head module is located at the core of the Mediator complex and serves as the point of contact with transcription factors and enhancer-bound coactivators. It contains Med17, Med18, Med20, Med22, Med31, and Med34 subunits. The Head module facilitates the interaction between Mediator and various transcription factors, allowing them to recruit the complex to specific genes. The Middle module of Mediator includes Med1, Med4, Med7, Med9, Med10, Med21, and Med33 subunits. It acts as a bridge between the Head and Tail modules and contributes to the stability of the entire complex. Med1 is a prominent subunit in this module and plays a critical role in enhancer-mediated gene activation. The Tail module contains subunits like Med2, Med3, Med5, Med15, Med16, Med23, and Med30. The Tail module interacts with RNAPII and general transcription factors, facilitating the assembly of the pre-initiation complex (PIC) at the promoter. The Kinase module, also known as the Cdk8 module, consists of Med12, Med13, Cyclin C, and Cdk8 subunits. This module has kinase activity and can phosphorylate both transcription factors and other Mediator subunits, thereby regulating the transcriptional process. The Kinase module can also phosphorylate the C-terminal domain (CTD) of RNAPII and transcription factors. This phosphorylation can either enhance or inhibit transcription, depending upon the context. One of the primary functions of the Mediator complex is to facilitate communication between enhancer regions, where transcription factors bind, and gene promoters, where RNAPII initiates transcription. The Mediator acts as a molecular bridge, helping to transmit regulatory signals from enhancers to promoters. The Mediator complex is also essential for the formation of the pre-initiation complex (PIC) at gene promoters. It interacts with RNAPII and general transcription factors (such as TFIID) to facilitate the assembly of the PIC. This step is critical for the efficient initiation of transcription. The Mediator complex can both activate and repress gene transcription, depending on the context. It achieves this by interacting with different transcription factors and coactivators or corepressors. For example, when interacting with activators, the Mediator complex promotes gene expression. For example, transcriptional activators such as the estrogen receptor (ER), androgen receptor (AR), and glucocorticoid receptor (GR) interact with the Mediator complex to initiate transcription of hormone-responsive genes, with Mediator facilitating the formation of a transcription initiation complex in response to hormone binding. We offer a comprehensive product catalogue of research tools for studying the mediator complex, including SNF5 antibodies, SURF5 antibodies, and Cdk8 antibodies. Explore our full mediator complex product range below and discover more, for less.