Transcriptional control of Nramp 1:: a paradigm for the repressive action of c-Myc

Slc11a1/Nramp1 (solute carrier family 11 member a1/murine natural resistance-associated macrophage protein 1 gene) encodes a divalent cation transporter that resides within lysosomes/late endosomes of macrophages. Nramp1 modulates the cellular distribution of divalent cations in response to cell activation by intracellular pathogens. Nramp1 expression is repressed and activated by the proto-oncogene c-Myc and Miz-1 (c-Myc-interacting zinc finger protein 1) respectively. Here we demonstrate, using a c-Myc mutant (V394D, Val(394) --> Asp) that is incapable of binding Miz-1, that c-Myc repression of Nramp1 transcription is dependent on its interaction with Miz-1. An oligo pull-down assay demonstrates specific binding of recombinant Miz-1 to the Nramp1 Miz-1-binding site or initiator element(s), and Miz-1-dependent c-Myc recruitment.