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Functional mapping of androgen receptor enhancer activity

2021    Huang, Chia-Chi Flora; Lingadahalli, Shreyas; Morova, Tunc; Ozturan, Dogancan; Hu, Eugene; Yu, Ivan Pak Lok; Linder, Simon; Hoogstraat, Marlous; Stelloo, Suzan; Sar, Funda; van der Poel, Henk; Altintas, Umut Berkay; Saffarzadeh, Mohammadali; Le Bihan, Stephane; McConeghy, Brian; Gokbayrak, Bengul; Feng, Felix Y.; Gleave, Martin E.; Bergman, Andries M.; Collins, Colin; Collins, Colin

Background Androgen receptor (AR) is critical to the initiation, growth, and progression of prostate cancer. Once activated, the AR binds to cis-regulatory enhancer elements on DNA that drive gene expression. Yet, there are 10-100x more binding sites than differentially expressed genes. It is unclear how or if these excess binding sites impact gene transcription. Results To characterize the regulatory logic of AR-mediated transcription, we generated a locus-specific map of enhancer activity by functionally testing all common clinical AR binding sites with Self-Transcribing Active Regulatory Regions sequencing (STARRseq). Only 7% of AR binding sites displayed androgen-dependent enhancer activity. Instead, the vast majority of AR binding sites were either inactive or constitutively active enhancers. These annotations strongly correlated with enhancer-associated features of both in vitro cell lines and clinical prostate cancer samples. Evaluating the effect of each enhancer class on transcription, we found that AR-regulated enhancers frequently interact with promoters and form central chromosomal loops that are required for transcription. Somatic mutations of these critical AR-regulated enhancers often impact enhancer activity. Conclusions Using a functional map of AR enhancer activity, we demonstrated that AR-regulated enhancers act as a regulatory hub that increases interactions with other AR binding sites and gene promoters.