It is generally accepted that site-specific transcription factors, such as steroid receptors, stimulate gene expression by promoting the assembly of basal transcription factors (TF) into a stable preinitiation complex that facilitates an increased rate of transcription initiation by RNA polymerase II. Although the ER can interact directly with TFIIB, positively acting factors, termed coactivators, are envisioned to serve as bridging factors between specific activators and general transcription factors. buy flovent inhaler
Although many hormone-dependent, ER-interacting proteins have been identified, only a subset consisting of SRC-1, TIF2 (and its murine homolog, GRIP1), p/CIP (also known as ACTR, RAC3, or AIB1) and СВР significantly stimulate (> 3-fold) ER-mediated transcription. Notably, SRC-1, TIF2, and p/CIP share extensive homology, and it is likely that they comprise a family of steroid receptor coactivators. In addition to the ability of СВР to synergize with SRC-1 in the activation of steroid receptor-dependent transcription, СВР also serves as a coactivator for a diverse array of transcription factors including c-Myb, c-Fos, and c-Jun, and in this role it appears to serve as an integrator protein.