The endonucleolytic cleavage step of the eukaryotic mRNA 3'-end processing is considered imprecise, which leads to heterogeneity of cleavage site (CS) with hitherto unknown function. Contrary to popular belief, we show that this imprecision in the cleavage is tightly regulated, resulting in the CS heterogeneity (CSH) that controls gene expression in antioxidant response. CSH centres around a primary CS, followed by several subsidiary cleavages determined by CS's positions. Globally and using reporter antioxidant mRNA, we discovered an inverse relationship between the number of CS and the gene expression, with the primary CS exhibiting the highest cleavage efficiency. Strikingly, reducing CSH and increasing primary CS usage induces gene expression. Under oxidative stress (we employ three conditions that induce antioxidant response, tBHQ, H