Identification of the human zinc transcriptional regulatory element (ZTRE): a palindromic protein-binding DNA sequence responsible for zinc-induced transcriptional repression.

Many genes with crucial roles in zinc homeostasis in mammals respond to fluctuating zinc supply through unknown mechanisms, and uncovering these mechanisms is essential to understanding the process at cellular and systemic levels. We detected zinc-dependent binding of a zinc-induced protein to a specific sequence, the zinc transcriptional regulatory element (ZTRE), in the SLC30A5 (zinc transporter ZnT5) promoter and showed that substitution of the ZTRE abrogated the repression of a reporter gene in response to zinc. We identified the ZTRE in other genes, including (through an unbiased search) the CBWD genes and (through targeted analysis) in multiple members of the SLC30 family, including SLC30A10, which is repressed by zinc. The function of the CBWD genes is currently unknown, but roles for homologs in metal homeostasis are being uncovered in bacteria. We demonstrated that CBWD genes are repressed by zinc and that substitution of the ZTRE in SLC30A10 and CBWD promoter-reporter constructs abrogates this response. Other metals did not affect expression of the transcriptional regulator, binding to the ZTRE or promoter-driven reporter gene expression. These findings provide the basis for elucidating how regulation of a network of genes through this novel mechanism contributes to zinc homeostasis and how the cell orchestrates this response.