Fig 4.

ZEB1 and ZEB2 contents and their binding to the collagen Iα2 promoter in young (Y), middle-aged (M), and old (O) mice. Immunoblotting of equal amounts of renal cortical homogenates was performed to assess changes in the expression of ZEB1 (A) and ZEB2 (B) (*P < 0.05, **P < 0.01 vs. young, †††P < 0.001 vs. middle-aged mice by ANOVA, n = 6 mice in each group). Histograms of composite data for each protein are shown in the lower panels. (C) Chromatin immunoprecipitation (ChIP) assay was performed for the binding of ZEB1, ZEB2, and RNA polymerase II (RNA Pol II) to the collagen type Iα2 promoter as described in Methods. There was no significant change in ZEB1 binding to the promoter. ZEB2 binding to the promoter was decreased in the middle-aged and old mice (**P < 0.01 vs. young by ANOVA, n = 4–6 mice in each group). RNA Pol II binding to the promoter was increased progressively with aging (**P < 0.01 vs. young, ††P < 0.01 vs. middle-aged mice by ANOVA, n = 4–6 mice in each group).