Androgen receptor-mediated repression of novel target genes.
BACKGROUND
The androgen receptor (AR) plays a pivotal role in prostate cancer (PCa) initiation and progression. To date, studies have focused disproportionately on androgen-stimulated genes such as prostate-specific antigen (PSA), while repressed genes have gained little attention, even though they too may be involved in regulating cell growth, differentiation, and apoptosis.


METHODS
ChIP Display was used to identify putative AR target genes in the ablation-resistant human PCa cell line, C4-2B. Quantitative real-time reverse transcription-PCR analysis was used to measure gene expression in cells subjected to dihydrotestosterone (DHT) timecourse and dose-response, as well as AR knock-down and bicalutamide-treatments.


RESULTS
We report on three genes, KIAA1217, CHRM1, and WBSCR28, which were newly identified in a screen for AR-occupied regions in C4-2B PCa cells, and which were repressed by treatment with DHT. AR knock-down resulted in increased KIAA1217, CHRM1, and WBSCR28 mRNA, indicating that, like PSA stimulation, AR represses these three genes even in the absence of added ligand. DHT decreased KIAA1217 and CHRM1 pre-mRNA levels, suggesting AR-mediated transcriptional inhibition. Cycloheximide attenuated DHT-mediated repression of CHRM1, suggesting the requirement of new protein synthesis. Furthermore, bicalutamide treatment did not mimic, but rather antagonized DHT-mediated KIAA1217 repression. Unlike the handful of androgen-repressed genes studied thus far, AR occupancy at KIAA1217, CHRM1, and WBSCR28 was mapped outside their respective 5'-promoter regions.


CONCLUSIONS
Many more genes likely share AR-mediated gene repression through distal regulatory elements. Further study of such targets and their transcriptional regulation may help explain the receptor's tumorigenicity in PCa.
Prescott
Jennifer
J
Department of Preventive Medicine, Norris Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, California, USA.
Jariwala
Unnati
U
Jia
Li
L
Cogan
Jon P
JP
Barski
Artem
A
Pregizer
Steve
S
Shen
Howard C
HC
Arasheben
Armin
A
Neilson
Jessica J
JJ
Frenkel
Baruch
B
Coetzee
Gerhard A
GA
D000726:Androgen Antagonists / Q000494:pharmacology; D000813:Anilides / Q000494:pharmacology; D045744:Cell Line, Tumor; D003513:Cycloheximide / Q000494:pharmacology; D013196:Dihydrotestosterone / Q000494:pharmacology; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008297:Male; D009570:Nitriles / Q000494:pharmacology; D011471:Prostatic Neoplasms / Q000235:genetics* / Q000378:metabolism; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D043643:Receptor, Muscarinic M1; D011944:Receptors, Androgen / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D011976:Receptors, Muscarinic / Q000096:biosynthesis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014105:Tosyl Compounds / Q000494:pharmacology; D014162:Transfection
D000726:Androgen Antagonists; D000813:Anilides; C086088:CHRM1 protein, human; D009570:Nitriles; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D043643:Receptor, Muscarinic M1; D011944:Receptors, Androgen; D011976:Receptors, Muscarinic; D014105:Tosyl Compounds; D013196:Dihydrotestosterone; D003513:Cycloheximide; C053541:bicalutamide