Figure 1.

Estrogen receptor alpha (ERα) is an activator of PARN-mediated nuclear deadenylation in MCF7 (ERα+) cells. (A) nuclear extracts (NEs) for cells treated with different concentrations of 17β-estradiol (E₂) for the indicated times were used in in vitro deadenylation assays with radiolabeled capped L3(A₃₀) RNA substrate. Purified RNA was analysed by denaturing PAGE. Left panel: representative deadenylation reactions from three independent biological assays are shown. Positions of the polyadenylated RNA L3(A₃₀) and the L3 deadenylated product are indicated. Right panel: bar graph of relative deadenylation (RD) is shown. (B–C) in vitro deadenylation assays using NEs from cells treated with (B) control (CTRL) or ERα siRNA for 24 h or (C) with increasing concentrations of fulvestrant for 2 h (FVT) were performed and analysed as in (A). (D) MCF7 cells were treated with either CTRL or PARN siRNA and subsequently treated with vehicle or E₂. NEs were used for in vitro deadenylation as performed and analysed in (A). E) Cell-free deadenylation assays were performed in the presence of radiolabeled capped L3(A₃₀) RNA substrates, limiting amount of his-PARN deadenylase and his-ERα and increasing amounts of GST-p53. Conditions for deadenylation assays were performed as in (A). F) NEs from untreated cells were used in endogenous reciprocal co-immunoprecipitation (e-ip) assays with polyclonal ERα, PARN, or p53 antibodies. NEs were treated with RNase A. Equivalent amounts of pellets (IP) and supernatants (SN) were resolved by SDS-PAGE, and proteins were detected by Western blot. Topo II was used as loading and IP specificity control. Ten percent of the NEs used in the e-ip assays are shown as input. All figures show representative deadenylation reactions and Western blot analyses from at least three independent biological assays analysed by triplicate (n = 3). Experiments with two groups were analysed using two-tailed unpaired Student’s t-test. The p-values are indicated as *(<0.01), **(<0.001) and ***(<0.0001).