FIG 4.

Phosphorylation in the regulatory domain suppresses HSF1 transactivating capacity. (A) hsf1^−/− MEFs were transfected with Mock plasmid [pcDNA3.1/myc-His(−)A], Myc-His-HSF1 WT, or Myc-His-HSF1Δ∼PRD and left either untreated (C) or exposed to heat stress at 43°C up to 60 min. The mRNA levels of HSPA1A/B (Hsp70) and HSPB1 (Hsp25) were quantified with qRT-PCR and normalized against RNA18S5. The values are shown relative to the respective mRNA levels in the Mock-transfected cells in control conditions (C), which was arbitrarily set to value 1. (B) hsf1^−/− MEFs were transfected as in panel A and either left untreated (C), treated with 60 μM CdSO₄ for 3 h (3 h), or treated for 3 h and left to recover in fresh culture medium for 3 h (3 h + R3h). mRNA quantification and data analysis were performed as in panel A. The data are presented as mean values from at least three independent experiments plus the SEM. *, P ≤ 0.05; ***, P ≤ 0.001; ****, P ≤ 0.0001.