FIGURE 4.

Inhibition of calpain by calpeptin in K562 cells increases β-globin gene expression and Pol II interactions with the β-globin promoter and LCR core element HS2. A, relative increase in β-globin mRNA levels following treatment of K562 cells with 40 μm calpain inhibitor calpeptin for 7 days. RNA was isolated, reverse transcribed, and subjected to quantitative PCR analysis using primers specific for the human β-, γ-, and ϵ-globin genes as well as the β-actin gene. The mRNA levels are shown as -fold increase in cells treated with calpeptin relative to levels in untreated cells. B, ChIP analysis of USF and Pol II interactions with LCR element HS2 and the β-globin gene promoter in K562 cells grown in the presence (plus calpeptin) or absence (control) of calpeptin. Cells were subjected to ChIP analysis using antibodies specific for USF1 and RNA Pol II as indicated. Precipitated DNA was analyzed by quantitative PCR using primers specific for LCR element HS2 or the β-globin gene promoter. Error bars reflect S.D. from two independent experiments.