Figure 3.

Nucleosome depletion does not inhibit GR function but hinders the synergistic activation of MMTV promoter by GR and NFI. (A) A yeast strain with the histone H4 gene under Gal control was transformed with the episomal GRE–lacZ reporter described in the scheme, together with an expression vector for rat GR (27). Cultures were incubated with ligand or vehicle after switching cells from galactose (Gal) to glucose (Glu) or keeping them in galactose. β-Galactosidase activities are shown. (B Left) β-Galactosidase activities obtained in experiments similar to those described in A but using the MMTV–lacZ reporter depicted in Fig. 2A. (Right) Results obtained from a yeast strain with the histone H4 gene driven by its own promoter. (C) Functional synergism between GR and NFI. Synergism is defined as the ratio of the activity found in the presence of GR/DAC and NFI over the sum of the activity found with GR/DAC in the absence of NFI and the activity measured with NFI in the absence of GR/DAC (Fig. 2A Right). (D) Similar experiments to those described in B but in strains additionally transformed with an NFI-expressing vector.