Sheflin L G, Brooks E M, Keegan B P, Spaulding S W
Medical Research Service (151), Veterans Affairs Western New York Healthcare System, Buffalo 14215, USA.
Endocrinology. 1996 Dec;137(12):5616-23. doi: 10.1210/endo.137.12.8940392.
The submaxillary gland (SMG) of the male mouse is known to contain more epidermal growth factor (EGF) messenger RNA (mRNA) than that of the female. In contrast, the SMG of female mice contains more of a cytosolic 47-kDa RNA binding protein that binds to a unique 23-b sequence at the end of the 3' untranslated region (3' UTR) of EGF, which includes the canonical polyadenylation signal in an AU-rich region containing a potential mRNA destabilizing sequence. Testosterone treatment can change the activity of this 47-kDa protein within 1 day, which precedes the change produced in the level and in the polyadenylation of EGF mRNA in female mice. In the kidney, however, neither the 47-kDa protein nor the polyadenylation pattern changed after testosterone. We now report that 2 weeks following orchiectomy of Balb/c mice, mature EGF peptide immunoreactivity levels fall by 96% (P < 0.0002), and mRNA levels fall by 76% (P < 0.0001). Orchiectomy also enhances the RNA binding activities of the 47-kDa protein in SMG cytosol but not in the kidney: UV cross-linking to 3' UTR RNA is increased by 67% (P < 0.01) and shifting of the gel mobility of the RNA is increased by 47% (P < 0.05). The polyadenylation pattern of EGF transcripts also changes in SMG but not in kidney cytosol. After orchiectomy, the population of EGF transcripts in the SMG with short, heterogenous poly-A tails (<50 A's) decreases by 31% (P < 0.03), whereas transcripts with long poly-A tails of approximately 50, 70, 100, and 200 A's all increase and become more distinct, resembling the pattern found in the normal female. Thus, 2 weeks after orchiectomy, the responses in EGF expression, EGF mRNA polyadenylation, and the activities of the 47-kDa 3' UTR binding protein are the reciprocal of the responses produced by injecting female mice with testosterone for 5 days, providing further evidence that circulating androgens regulate EGF expression posttranscriptionally in a sexually dimorphic, tissue-specific fashion.
已知雄性小鼠的颌下腺（SMG）所含的表皮生长因子（EGF）信使核糖核酸（mRNA）比雌性小鼠的多。相比之下，雌性小鼠的颌下腺含有更多一种胞质47 kDa RNA结合蛋白，该蛋白可与EGF 3'非翻译区（3'UTR）末端一个独特的23碱基序列结合，该序列在富含AU的区域包含典型的多聚腺苷酸化信号，其中含有一个潜在的mRNA不稳定序列。睾酮处理可在1天内改变这种47 kDa蛋白的活性，这早于雌性小鼠中EGF mRNA水平和多聚腺苷酸化的变化。然而，在肾脏中，睾酮处理后47 kDa蛋白和多聚腺苷酸化模式均未改变。我们现在报告，Balb/c小鼠睾丸切除术后2周，成熟EGF肽免疫反应性水平下降96%（P < 0.0002），mRNA水平下降76%（P < 0.0001）。睾丸切除术还增强了颌下腺胞质中47 kDa蛋白的RNA结合活性，但在肾脏中未增强：与3'UTR RNA的紫外线交联增加了67%（P < 0.01），RNA凝胶迁移率的改变增加了47%（P < 0.05）。EGF转录本的多聚腺苷酸化模式在颌下腺中也发生了变化，但在肾脏胞质中未变。睾丸切除术后，颌下腺中具有短的、异质性多聚A尾（<50个A）的EGF转录本群体减少了31%（P < 0.03），而具有约50、70、100和200个A的长多聚A尾的转录本均增加且变得更加明显，类似于正常雌性中的模式。因此，睾丸切除术后2周，EGF表达、EGF mRNA多聚腺苷酸化以及47 kDa 3'UTR结合蛋白活性的反应与给雌性小鼠注射睾酮5天所产生的反应相反，这进一步证明循环雄激素以性别二态性、组织特异性方式在转录后调节EGF表达。
