Mediator is a large complex of up to 33 proteins that is conserved from plants to fungi to humans - the number and representation of individual subunits varying with species [1-2]. It is arranged into four different sections, a core, a head, a tail and a kinase-active part, and the number of subunits within each of these is what varies with species. Overall, Mediator regulates the transcriptional activity of RNA polymerase II but it would appear that each of the four different sections has a slightly different function [3]. Med29, along with Med11 and Med28, in mammals, is part of the core head-region of the complex. Med29 is the apparent orthologue of the Drosophila melanogaster Intersex protein, which interacts directly with, and functions as a transcriptional coactivator for, the DNA-binding transcription factor Doublesex, so it is likely that mammalian Med29 serves as a target for one or more DNA-binding transcriptional activators [4].

1: A unified nomenclature for protein subunits of mediator complexes linking transcriptional regulators to RNA polymerase II. Bourbon HM, Aguilera A, Ansari AZ, Asturias FJ, Berk AJ, Bjorklund S, Blackwell TK, Borggrefe T, Carey M, Carlson M, Conaway JW, Conaway RC, Emmons SW, Fondell JD, Freedman LP, Fukasawa T, Gustafsson CM, Han M, He X, Herman PK, Hinnebusch AG, Holmberg S, Mol Cell. 2004;14:553-557. PMID:15175151

2: A set of consensus mammalian mediator subunits identified by multidimensional protein identification technology. Sato S, Tomomori-Sato C, Parmely TJ, Florens L, Zybailov B, Swanson SK, Banks CA, Jin J, Cai Y, Washburn MP, Conaway JW, Conaway RC; Mol Cell. 2004;14:685-691. PMID:15175163

3: Structure-system correlation identifies a gene regulatory Mediator submodule. Lariviere L, Seizl M, van Wageningen S, Rother S, van de Pasch L, Feldmann H, Strasser K, Hahn S, Holstege FC, Cramer P; Genes Dev. 2008;22:872-877. PMID:18381891

4: The mammalian Mediator complex and its role in transcriptional regulation. Conaway RC, Sato S, Tomomori-Sato C, Yao T, Conaway JW; Trends Biochem Sci. 2005;30:250-255. PMID:15896743