Coregulator Recruitment and Histone Modifications in Transcriptional Regulation by the Androgen Receptor

Abstract

We have used chromatin immunoprecipitation (ChIP) assay to follow transcription factor loading and monitor changes in covalent histone modifications associated with the prostate-specific antigen and kallikrein (KLK2) genes in response to androgen and antiandrogen in LNCaP cells. The dynamics of testosterone (T)-induced loading of androgen receptor (AR) onto the proximal promoters of the genes differed significantly from that onto the distal enhancers. Significantly more holo-AR was loaded onto the enhancers than the promoters, but the receptor's residence time was more transient on the enhancers. Even though holo-AR recruited some RNA polymerase II (Pol II) onto the enhancers, the principal Pol II transcription complex was assembled on the promoters. The pure antiandrogen bicalutamide (CDX) complexed to AR elicited occupancy of the prostate-specific antigen promoter, but not that of the enhancer, whereas the partial antagonists cyproterone acetate (CPA) and mifepristone (RU486) were capable of promoting AR loading also onto the enhancer. In contrast to the CDX-occupied receptor, both CPA- and RU486-bound AR recruited Pol II and coactivators p300 and glucocorticoid receptor-interacting protein 1 (GRIP1) onto the promoter and enhancer. However, CPA and RU486 also brought about a simultaneous recruitment of the nuclear receptor corepressor (NCOR) onto the promoter as efficiently as CDX. There were dynamic changes in covalent modifications of histone H3: acetylation of lysine 9 and 14, methylation of arginine 17, phosphorylation of serine 10 as well as di- and tri-methylation at lysine 4 of the H3 N-terminal tail were enhanced in response to T, but not after CDX treatment. Collectively, these results indicate that transcriptional activation by AR is accompanied by a cascade of distinct covalent histone modifications and that the pure antiandrogen CDX and the partial antagonists CPA and RU486 exhibit clear differences in their ability to promote recruitment of histone-acetylating and histone-deacetylating complexes in human prostate cancer cells.

Androgen receptor activity is inhibited in response to genotoxic agents in a p53-independent manner

“…DHTinduced recruitment of AR to the AREIII was more pronounced than that to the AREI. This observation is in accordance with previous reports showing that more AR is recruited to the AREIII than to the AREI in response to androgen stimulation (Louie et al, 2003;Kang et al, 2004). For this reason, we decided to focus on AR recruitment to AREIII.…”

Androgen receptor signalling in prostate: Effects of stromal factors on normal and cancer stem cells

“…However, Kang et al, (2004) found that 200X more AR was loaded on to the enhancer compared to the promoter ARE of the PSA gene, but both promoter and enhancer ARE were needed for maximal activity. Conversely, more RNA polymerase II transcription factor was recruited to the promoter ARE.…”

“…Conversely, more RNA polymerase II transcription factor was recruited to the promoter ARE. Differential histone acetylation modifications were noted between the promoter and enhancer ARE of PSA with the promoter ARE dependent on RNA polymerase II phosphorylation (Kang et al, 2004, Wang et al, 2005.…”

Androgen receptor phosphorylation and stabilization in prostate cancer by cyclin-dependent kinase 1

“…Chromatin immunoprecipitation studies in LNCaP cells have shown that DHT stimulates the very rapid (within 15 min) recruitment of AR and coactivator proteins to endogenous androgen-regulated genes, including the PSA gene (36,37). Therefore, time course studies were done to assess whether Ser-81 phosphorylation was linked to chromatin recruitment of the endogenous AR in PCa cells.…”