Structure of the MED-1 divergent GATA factor

Although MED-1 is a putative GATA factor, the DNA binding site, as determined by DNaseI footprinting of MED-1 with the promoters of its targets end-1 and end-3, is a non-canonical site containing the core sequence GTATAC. Pairs of these sites are found upstream of several genes expressed in the early E and MS lineages.

MED binding site

MED-1 binding site based on footprinting of the end-1 and end-3 promoters

MED-1-DNA complex
Our collaborators at University of Sydney (the laboratory of Joel Mackay) have determined the solution structure of the DNA-binding domain of MED-1. Shown at left is a model that shows how the DNA-binding domain of MED-1 is proposed to interact with the core recognition sequence (GTATAC). To the right of this is shown a model of how a canonical GATA factor (GATA-1) interacts with its core sequence (AGATAA). An additional alpha helix is predicted to form in the carboxyl region, which is partly responsible for extending the consensus sequence. As MED-1 orthologs appear to exist only in the genus Caenorhabditis, this subclass of GATA factors appears to be a very recent invention.

Other current efforts of the collaboration include further refinement of the structure of the zinc finger of MED-1, and characterization of structure-function requirements for MED-1 function in vivo.

Identification of the MED-1 binding site: arrowBroitman-Maduro et al. (2005)
Evolution of MED-1 structure in C. briggsae and C. remanei: arrowCoroian et al. (2006)
Collaborative paper on MED-1 structure:  arrow
Lowry et al. (2009)