Hu Dong Gui, McKinnon Ross A, Hulin Julie-Ann, Mackenzie Peter I, Meech Robyn
Department of Clinical Pharmacology and Flinders Centre for Innovation in Cancer, Flinders University School of Medicine, Flinders Medical Centre, Adelaide 5042, Australia.
Int J Mol Sci. 2016 Dec 27;18(1):40. doi: 10.3390/ijms18010040.
Nearly 20 different transcripts of the human androgen receptor (AR) are reported with two currently listed as Refseq isoforms in the NCBI database. Isoform 1 encodes wild-type AR (type 1 AR) and isoform 2 encodes the variant AR45 (type 2 AR). Both variants contain eight exons: they share common exons 2-8 but differ in exon 1 with the canonical exon 1 in isoform 1 and the variant exon 1b in isoform 2. Splicing of exon 1 or exon 1b is reported to be mutually exclusive. In this study, we identified a novel exon 1b (1b/TAG) that contains an additional TAG trinucleotide upstream of exon 1b. Moreover, we identified AR transcripts in both normal and cancerous breast and prostate cells that contained either exon 1b or 1b/TAG spliced between the canonical exon 1 and exon 2, generating nine-exon AR transcripts that we have named isoforms 3a and 3b. The proteins encoded by these new AR variants could regulate androgen-responsive reporters in breast and prostate cancer cells under androgen-depleted conditions. Analysis of type 3 AR-GFP fusion proteins showed partial nuclear localization in PC3 cells under androgen-depleted conditions, supporting androgen-independent activation of the AR. Type 3 AR proteins inhibited androgen-induced growth of LNCaP cells. Microarray analysis identified a small set of type 3a AR target genes in LNCaP cells, including genes known to modulate growth and proliferation of prostate cancer (, , , and ) or other types of human cancers (, , and ), and genes that are diagnostic/prognostic biomarkers of prostate cancer (, and ).
据报道，人类雄激素受体（AR）有近20种不同的转录本，其中两种目前在NCBI数据库中列为Refseq亚型。亚型1编码野生型AR（1型AR），亚型2编码变体AR45（2型AR）。这两种变体都包含八个外显子：它们共享外显子2 - 8，但外显子1不同，亚型1中的外显子1是典型外显子，亚型2中的外显子1是变体外显子1b。据报道，外显子1或外显子1b的剪接是相互排斥的。在本研究中，我们鉴定出一种新的外显子1b（1b/TAG），它在其上游还包含一个额外的TAG三核苷酸。此外，我们在正常和癌性乳腺及前列腺细胞中均鉴定出AR转录本，这些转录本包含剪接在典型外显子1和外显子2之间的外显子1b或1b/TAG，产生了我们命名为亚型3a和3b的九外显子AR转录本。这些新的AR变体所编码的蛋白质在雄激素缺乏条件下可调节乳腺癌和前列腺癌细胞中的雄激素反应性报告基因。对3型AR - GFP融合蛋白的分析表明，在雄激素缺乏条件下，其在PC3细胞中部分定位于细胞核，支持AR的雄激素非依赖性激活。3型AR蛋白抑制雄激素诱导的LNCaP细胞生长。微阵列分析在LNCaP细胞中鉴定出一小部分3a型AR靶基因，包括已知可调节前列腺癌（、、、和）或其他类型人类癌症（、、和）生长和增殖的基因，以及作为前列腺癌诊断/预后生物标志物的基因（、和）。
