Thomas MA, Preece DM, Bentel JM
Androgen regulation of the prostatic tumour suppressor NKX3.1 is mediated by its 3'untranslated region. [JOURNAL ARTICLE]
Biochem J 2009 Nov 3.
The homeodomain transcription factor NKX3.1 is a prostate-specific tumour suppressor, expression of which is reduced or undetectable in the majority of metastatic prostate tumours. In the normal prostate and in prostate cancer cells, NKX3.1 expression is under tight androgenic control that we have shown to be mediated by its ~2.5kb 3' untranslated region (3'UTR). Reporter deletion analysis of the NKX3.1 3'UTR identified three regions that were transactivated by 5alpha-dihydrotestosterone (DHT) in the androgen receptor (AR)-expressing prostate cancer cell line, LNCaP. Reversal of DHT effects by the antiandrogen, bicalutamide supported an AR-mediated mechanism and bioinformatic analysis of the NKX3.1 3'UTR identified canonical androgen response elements (AREs) in each of the androgen-responsive regions. Electromobility shift assays (EMSAs) indicated binding of the AR DNA binding domain to two of the AREs, a proximal ARE at +2378-2392 from the transcription start site, and a more distal ARE at +3098-3112. ChIP analysis provided further evidence of ligand-dependent recruitment of endogenous AR to sequence encompassing each of the two elements and site-directed mutagenesis and deletion analysis confirmed the contribution of each of the AREs in reporter assays. These studies have therefore demonstrated that the NKX3.1 3'UTR functions as an androgen responsive enhancer with the proximal ARE contributing the majority and the distal ARE providing a smaller but significant proportion of the androgen responsiveness of the NKX3.1 3'UTR. Characterisation of androgen-responsive regions of the NKX3.1 gene will assist in the identification of transcriptional regulatory mechanisms that lead to the deregulation of NKX3.1 expression in advanced prostate cancers.
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