Regulation of steroid-5-alpha-reductase 2 (SRD5A2) in human prostate by epigenetic modifications.

Abstract

204 Background: 5-alpha reductase type 2 (SRD5A2), an enzyme that is critical for prostatic development and growth. We have found that many aging prostate tissues do not express the enzyme. We previously showed that expression of SRD5A2 is not static and epigenetic modulations by DNA methyltransferase and pro-inflammatory cytokines play important roles in silencing of SRD5A2. Here we wished to define the methylation pattern and identify specific CpG dinucleotides that are methylated in the SRD5A2promoter region. Methods: Ninety six prostate samples from patients were obtained by transurethral resection of prostate (TURP). Methylation of SRD5A2 promoter was assessed using Methylated CpG Island Recovery Assay (MIRA). Bisulfide conversion of Genomic DNA was performed using Epimark bisulfide conversion kit. Primers for bisulfide sequencing were designed using MethPrimer software and bisulfide sequencing was performed using 3730XL DNA Sequencers. Binding of histone demethylase to promoter DNA was analyzed by ChiP assay. Results: We randomly selected 3 TURP samples with methylated SRD5A2 promoters and 3 TURP samples with un-methylated SRD5A2 promoters, and then bisulfide conversion and sequencing were performed to verify the methylation pattern of CpG dinucleotides on SRD5A2 promoter. We found that bisulfide sequencing analysis of SRD5A2 promoter was consistent with MIRA analysis. To further analyze the mediators of SRD5A2 promoter region, we show that TNF-alpha up-regulates expression of Snail protein, which is a central regulator of both DNA methylation and histone methylation, and increases the binding of H3K9me to SRD5A2promoter region, but not H3K27me or H4K20me. Conclusions: Methylation of SRD5A2 promoter, which is regulated by DNMT1, proinflammatory cytokines and the histone methylase, H3K9me, accounts for suppression of SRD5A2 in many adult human prostate tissues. Bisulfide conversion and sequencing confirm and focus the specified CpG dinucleotides that are methylated enabling us to evaluate mechanisms and patterns of SRD5A2 promoter methylation in order to study the functional significance of SRD5A2 methylation. Grant support: NIH/R01 DK091353.