Krause William C, Shafi Ayesha A, Nakka Manjula, Weigel Nancy L
Department of Molecular and Cellular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.
Department of Molecular and Cellular Biology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030, USA.
Int J Biochem Cell Biol. 2014 Sep;54:49-59. doi: 10.1016/j.biocel.2014.06.013. Epub 2014 Jul 4.
Prostate cancer (PCa) is an androgen-dependent disease, and tumors that are resistant to androgen ablation therapy often remain androgen receptor (AR) dependent. Among the contributors to castration-resistant PCa are AR splice variants that lack the ligand-binding domain (LBD). Instead, they have small amounts of unique sequence derived from cryptic exons or from out of frame translation. The AR-V7 (or AR3) variant is constitutively active and is expressed under conditions consistent with CRPC. AR-V7 is reported to regulate a transcriptional program that is similar but not identical to that of AR. However, it is unknown whether these differences are due to the unique sequence in AR-V7, or simply to loss of the LBD. To examine transcriptional regulation by AR-V7, we have used lentiviruses encoding AR-V7 (amino acids 1-627 of AR with the 16 amino acids unique to the variant) to prepare a derivative of the androgen-dependent LNCaP cells with inducible expression of AR-V7. An additional cell line was generated with regulated expression of AR-NTD (amino acids 1-660 of AR); this mutant lacks the LBD but does not have the AR-V7 specific sequence. We find that AR and AR-V7 have distinct activities on target genes that are co-regulated by FOXA1. Transcripts regulated by AR-V7 were similarly regulated by AR-NTD, indicating that loss of the LBD is sufficient for the observed differences. Differential regulation of target genes correlates with preferential recruitment of AR or AR-V7 to specific cis-regulatory DNA sequences providing an explanation for some of the observed differences in target gene regulation.
前列腺癌（PCa）是一种雄激素依赖性疾病，对雄激素剥夺疗法耐药的肿瘤通常仍依赖雄激素受体（AR）。去势抵抗性PCa的促成因素包括缺乏配体结合域（LBD）的AR剪接变体。相反，它们有少量源自隐蔽外显子或框外翻译的独特序列。AR-V7（或AR3）变体具有组成型活性，在与去势抵抗性前列腺癌（CRPC）一致的条件下表达。据报道，AR-V7调节一个与AR相似但不完全相同的转录程序。然而，尚不清楚这些差异是由于AR-V7中的独特序列，还是仅仅由于LBD的缺失。为了研究AR-V7的转录调控，我们使用编码AR-V7（AR的1-627个氨基酸以及该变体特有的16个氨基酸）的慢病毒来制备雄激素依赖性LNCaP细胞的衍生物，使其可诱导表达AR-V7。另外还构建了一个细胞系，其AR-NTD（AR的1-660个氨基酸）的表达受到调控；该突变体缺乏LBD但没有AR-V7特异性序列。我们发现，AR和AR-V7对由FOXA1共同调控的靶基因具有不同的活性。由AR-V7调控的转录本同样受到AR-NTD的调控，这表明LBD的缺失足以导致观察到的差异。靶基因的差异调控与AR或AR-V7优先募集到特定的顺式调控DNA序列相关，这为观察到的靶基因调控差异提供了一些解释。
