RBP4 gene expression is induced by HMGA1. (Top) Mouse RBP4-Luc reporter vector (2 μg) was transfected into HepG2 and Hepa1 cells plus increasing amounts (0, 0.5, or 1 μg) of HMGA1 expression plasmid. Data represent the means ± standard errors for three separate experiments; values are expressed as factors by which induced activity increased above the level of Luc activity obtained in transfections with RBP4-Luc reporter vector plus the empty expression vector, which is assigned an arbitrary value of 1. (Middle) HMGA1 expression plasmid was transfected into HepG2 and Hepa1cells. After 6 h of transfection, the cells were treated with anti-HMGA1 (100 pmol), siRNA, or a non-targeting control siRNA, and endogenous RBP4 mRNA expression was measured 48 to 96 h later. Western blots of HMGA1 in each condition are shown in the autoradiograms. (Bottom) ChIP of the RBP4 promoter gene in HepG2 and Hepa1 cells, either untreated or pretreated with HMGA1 siRNA. ChIP was done using an anti-HMGA1 specific antibody (Ab).