Fig. 7. (A) Immunoblotting analysis of JunB proteins in stable JunB–ER clones. Equal amounts of total extracts from β-oestradiol-stimulated NIH 3T3 control cells, NIH 3T3/JunB–ER clone 2 and clone 45 were separated by SDS–PAGE and probed for JunB. Labelled lanes indicate the position of the endogenous JunB protein and the ectopically expressed JunB–ER fusion protein of ∼80 kDa. (B) The JunB–ER protein activates transcription of a transiently transfected TRE reporter in a hormone-dependent fashion. Control and JunB–ER cells (clones B2 and B45) were transiently transfected with a collagenase–CAT construct and treated for 40 h with β-oestradiol or solvent. The values and standard deviation represent the results of three independent experiments. (C) The JunB–ER fusion protein is also subjected to Cdc2–cyclin B phosphorylation during mitosis. Equal amounts of total extracts from adherent (Adh) or mitotic (M) NIH 3T3/JunB–ER45 cells were separated by SDS–PAGE and probed for JunB.