Identification of an alternate promoter in the rat androgen-binding protein/sex hormone-binding globulin gene that regulates synthesis of a messenger RNA encoding a protein with altered function.
Identification of an alternate promoter in the rat androgen-binding protein/sex hormone-binding globulin gene that regulates synthesis of a messenger RNA encoding a protein with altered function.
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DOI：
10.1210/mend.7.5.7686253
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发表时间：
1993-05
影响因子：
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通讯作者：
Patrick F. Sullivan;Yan-min Wang;D. R. Joseph
中科院分区：
文献类型：
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作者：
Patrick F. Sullivan;Yan-min Wang;D. R. Joseph
细胞外雄激素结合蛋白（ABP）被认为可以调节雄激素的调节功能。这些蛋白质由睾丸 (ABP) 和肝脏 [性激素结合球蛋白 (SHBG)] 分泌，由同一基因编码。在之前的研究中，对大鼠 ABP/SHBG 基因进行了测序，并通过引物延伸鉴定了启动子（P1）。该启动子调节编码分泌性睾丸 ABP 和胎儿肝脏 SHBG 的 mRNA 的合成。在本研究中，通过 RNase 保护测定证实了睾丸和胎儿肝脏中的 P1 转录起始位点。我们还在 ABP/SHBG 基因中鉴定了一个替代启动子 (PA)，该启动子位于先前表征的睾丸启动子 (P1) 上游 15 KB。 PA区具有富含GC的管家型启动子的特征。 RNA酶保护和RNA聚合酶链式反应的引物步行实验确定了主要转录起始位点发生的区域。启动子 PA 指导替代 ABP RNA 的合成，其中包含替代外显子 1（外显子 A）序列。另一种 ABP RNA 包含外显子 A 和 2-8 序列，在睾丸、胎儿肝脏和大脑中表达。这种替代的 ABP RNA 编码一种 ABP 样蛋白（46,000 道尔顿），其 N 端序列发生改变，不含分泌信号肽。 COS 细胞中 ABP 样蛋白的表达表明它不是分泌的，并且似乎不结合二氢睾酮。另一种类似的替代 ABP RNA 缺少外显子 6 序列，并编码不结合雄激素的非分泌性截短蛋白（28,000 道尔顿）。 ABP样蛋白的功能并不明显，但其功能与分泌型ABP和SHBG明显不同。
Extracellular androgen-binding proteins (ABP) are thought to modulate the regulatory functions of androgens. These proteins, which are secreted by the testis (ABP) and liver [sex hormone-binding globulin (SHBG)], are encoded by the same gene. In a previous study, the rat ABP/SHBG gene was sequenced, and a promoter (P1) was identified by primer extension. This promoter regulates synthesis of the mRNA that encodes secreted testicular ABP and fetal liver SHBG. In this study, the P1 transcriptional start site in testis and fetal liver was confirmed by RNase protection assays. We also identified an alternate promoter (PA) in the ABP/SHBG gene located 15 kilobases up-stream from the previously characterized testicular promoter (P1). The PA region has the characteristics of a GC-rich housekeeping-type promoter. RNAase protection and primer walking experiments with RNA polymerase chain reaction identified a region where the major sites of transcription initiation occur. Promoter PA directs the synthesis of alternate ABP RNAs, which contain an alternate exon 1 (exon A) sequence. One alternate ABP RNA, which contains exons A and 2-8 sequences, is expressed in testis, fetal liver, and brain. This alternate ABP RNA encodes an ABP-like protein (46,000 daltons) with an altered N-terminal sequence without a secretory signal peptide. Expression of the ABP-like protein in COS cells revealed that it is not secreted and does not appear to bind dihydrotestosterone. Another similar alternate ABP RNA is missing exon 6 sequence and encodes a nonsecretory truncated protein (28,000 daltons) that does not bind androgen. The functions of the ABP-like proteins are not obvious, but their functions are clearly different from secreted ABP and SHBG.