Jiang H, Lucy M C
Department of Animal Sciences, 164 Animal Science Research Center, University of Missouri, 65211-5300, Columbia MO, USA.
Gene. 2001 Mar 7;265(1-2):45-53. doi: 10.1016/s0378-1119(01)00356-0.
The growth hormone receptor (GHR) gene in cattle is expressed as multiple GHR mRNA variants that differ in the 5'-untranslated region (5'-UTR). Three GHR mRNA 5'-UTR variants (named 1A, 1B, and 1C) were isolated in previous studies. Six additional GHR mRNA 5'-UTR variants (named 1D, 1E, 1F, 1G, 1H, and 1I) were discovered in the present study by using rapid amplification of cDNA ends (RACE). Ribonuclease protection assays (RPA) indicated that variant 1A was exclusively expressed in liver, variant 1F was expressed in liver and muscle, and most of the remaining GHR 5'-UTR variants were expressed in a variety of tissues including liver and muscle. The RPA also indicated that in liver and skeletal muscle, two important GH target tissues, the most abundant GHR mRNA 5'-UTR variants were 1A and 1B (liver) and 1B and 1C (muscle), respectively. In vitro translation assays indicated that the GHR 5'-UTR variants also differed in their effects on the translation of a luciferase reporter mRNA. Notably, the GHR 5'-UTR 1B, which is a highly expressed GHR 5'-UTR variant in vivo, strongly inhibited translation of the luciferase reporter mRNA. The observations in the present study suggest that GHR expression in the bovine may be controlled by translational mechanisms in addition to complex transcriptional mechanisms.
牛的生长激素受体（GHR）基因表达为多种GHR mRNA变体，这些变体在5'-非翻译区（5'-UTR）存在差异。先前的研究中分离出了三种GHR mRNA 5'-UTR变体（命名为1A、1B和1C）。在本研究中，通过使用cDNA末端快速扩增（RACE）又发现了另外六种GHR mRNA 5'-UTR变体（命名为1D、1E、1F、1G、1H和1I）。核糖核酸酶保护试验（RPA）表明，变体1A仅在肝脏中表达，变体1F在肝脏和肌肉中表达，其余大多数GHR 5'-UTR变体在包括肝脏和肌肉在内的多种组织中表达。RPA还表明，在肝脏和骨骼肌这两个重要的生长激素靶组织中，最丰富的GHR mRNA 5'-UTR变体分别是1A和1B（肝脏）以及1B和1C（肌肉）。体外翻译试验表明，GHR 5'-UTR变体对荧光素酶报告基因mRNA翻译的影响也存在差异。值得注意的是，GHR 5'-UTR 1B在体内是高表达的GHR 5'-UTR变体，它强烈抑制荧光素酶报告基因mRNA的翻译。本研究中的观察结果表明，除了复杂的转录机制外，牛体内的GHR表达可能还受翻译机制的控制。
