passages.id: split_5_test_143_passage
passages.type: progene_text
passages.text: Only the four active MREs efficiently bound the purified transcription factor human MTF-1 , and MRE mutants defective in binding this protein lost the ability to support zinc - induced reporter gene expression , strongly suggesting that the direct interaction between human MTF-1 and a set of the selected MREs plays the major role in heavy metal regulation .