THE LIVER-SPECIFIC PROMOTER OF THE HUMAN INSULIN-LIKE GROWTH FACTOR-II GENE CONTAINS 2 NEGATIVE REGULATORY ELEMENTS

The adult liver-specific IGF-II promoter P1 is activated by CCAAT/Enha ncer Binding Proteins alpha and beta. Here we present evidence that pr omoter P1, in addition to positively regulating elements, contains two elements of 67 nucleotides that form an inverted repeat (IR) and supp ress P1 activity, The two IR elements are specifically bound by a prot ein (inverted repeat binding factor, IRBF), The amounts of IRBF in var ious cell lines correlate with the levels of suppression of P1 activit y, suggesting that this factor is responsible for the suppression of P 1 mediated by the IR elements.