Figure 1. Model for PR binding to PREs organized in nucleosomes. (A) Functional PREs are exposed in well-positioned nucleosomes. A subset of these PREs is occupied by unliganded PR associated to a repressive complex containing HP1γ and SRA-RNA.7 On poorly positioned nucleosomes (upper left corner), PREs are not efficiently recognized by PR. (B) Upon hormone binding, the activated PR reaches these PREs in association with kinases, histone tails modifiers and NURF that stabilize PR binding via contact with histones and initiate chromatin remodeling (H1 displacement).8,9(C) In a subsequent step BAF catalyzes histone H2A/H2B displacement.10(D) After chromatin remodeling, PR interacts with other TFs, co-regulators and components of the transcriptional machinery, to promote formation of the transcription initiation complex.24