HSP27 interacts with GATA-1. (A) COS cells were cotransfected or not with Myc–GATA-1 and HA-HSP27. GATA-1 was immunoprecipitated from cell extracts, subjected to sodium dodecyl sulfate–polyacrylamide gel electrophoresis migration and immunoblotted with HA-tag (HSP27) antibody. Control for immunoprecipitation (IPCtl) corresponds to a mix of nonrelevant immunoglobulin G and protein G in the presence of lysate. Inputs: protein expression in total extracts. (B) Yeast 2 hybrid assay that detect a direct interaction of HSP27 with GATA-1 wild type (GATA-1-wt) and GATA-1 Δ1-83 (blue staining) but not with GATA-1 Δ84-413. Each section contains diploid yeast cells resulting from one independent yeast mating experience with the corresponding bait protein and a prey protein. The empty vector pGADT7 is used as a negative control. (C) Nuclear extracts from differentiating progenitors CD36⁺ cells were subjected to immunoprecipitation with GATA-1 antibody and blotted with HSP27 antibody. (D) Immunoprecipitation of endogenous GATA-1 (left) or HSP27 (right) from K562 cell lysates at indicated times of differentiation was followed by HSP27 and GATA-1 immunoblotting. IPCtl, immunoprecipitation in lysates from differentiating cells with a nonrelevant antibody and G protein. Inputs: protein expression in total extracts (40 μg).