FIG. 9.
Expression of endogenous AR target genes is regulated by CBP and Sir2. (A) ChIP assays with the indicated antibodies and PCR at the promoter of KLK2 gene were performed using MCF-7 and LNCaP cells treated with DHT for 4 h or left untreated. IgG, immunoglobulin G. (B) Western blotting measurement of the expression levels of CBP and SIRT1 in MCF-7 and LNCaP cells after transfection with the indicated siRNA. (C and D) MCF-7 (C) and LNCaP (D) cells were transfected with the indicated siRNA and treated with DHT (10−8 M) or left untreated. Induction of KLK2 expression is expressed as the ratio of KLK2 mRNA levels normalized to GAPDH levels between cells treated with vehicle or DHT. (E) Schematic illustration of CBP coregulator functions depending on the chromatin contexts. Based on the chromatin states, various transcription factors or coregulator complexes may be recruited to perform different functions in the euchromatic and pericentric regions. In the heterochromatic context, CBP and Sir2 recruited to AR target genes suppress the AR-mediated transactivation. A possible explanation for the repressive effect of CBP at the condensed environment is that CBP contributes to epigenetic silencing by acetylating chromatin proteins, such as Sir2, rather than histone. The CBP-mediated acetylation enhanced Sir2 HDAC activity and led to consecutive histone deacetylation.