Fig. 1. A subset of protein–protein interactions leading to ligand-regulated transcription by ERα. (A) A schematic representation of some of the interactions involved in ERα-mediated transcription, including interactions between (1) ERα and SRC proteins, (2) SRC proteins and p300/CBP and (3) p300/CBP and the RNA pol II machinery. (B) Schematic representations of p300, SRC2 and the protein fragments used in these studies. Top panel: schematic diagram of human p300. Specific regions of p300 are indicated: CREB-binding region, bromodomain (Bromo), histone acetyltransferase (HAT) domain, C/H3 domain/E1A-binding region, glutamine-rich region (Q-rich) and SRC interaction domain (SID). The residues included in the p300(SID) polypeptide are indicated. Bottom panel: schematic diagram of mouse SRC2. Specific regions of SRC2 are indicated: basic helix–loop–helix region (bHLH), Per-Arnt-Sim domain (PAS), nuclear receptor interaction domain (RID), p300/CBP interaction domain (PID) and glutamine-rich region (Q-rich). The residues included in the SRC2(RID/PID), SRC2(RID) and SRC2(PID) polypeptides are indicated.