Strobl J S, Dannies P S, Thompson E B
Biochemistry. 1986 Jun 17;25(12):3640-8. doi: 10.1021/bi00360a025.
The methylation status of the rat growth hormone (GH) gene was compared in DNA obtained from GH-producing and GH-nonproducing sources by digestion with three methylation-sensitive restriction enzymes. GH gene expression was correlated with an unmethylated ThaI site (CGCG) 144-bp upstream of the GH RNA transcription initiation site. This ThaI site was unmethylated in nine GH-producing subclones of the rat pituitary tissue culture cell line GH3 and in greater than 50% of the DNA isolated from rat anterior pituitary, a gland containing GH-producing somatotroph cells as well as GH-nonproducing cells. In DNA prepared from GH-nonproducing tissues, e.g., rat spleen, kidney, liver, and brain, this ThaI site was entirely methylated. Furthermore, this site was entirely methylated in hybrid cells formed by the fusion of GH3 cells with mouse fibroblasts in which GH production has been extinguished. DNA methylation at 10 other restriction sites located throughout the rat GH gene region failed to correlate with GH expression in GH-producing subclones of GH3 cells as well as in GH-nonproducing GH3 X LB82 hybrid cells. We suggest that the conserved absence of methylation 144 bp 5' of the RNA transcription initiation site of transcribed GH genes identifies a potential GH gene control region.
通过用三种对甲基化敏感的限制性内切酶消化，比较了从产生生长激素（GH）和不产生GH的来源获得的DNA中大鼠GH基因的甲基化状态。GH基因表达与GH RNA转录起始位点上游144 bp处未甲基化的ThaI位点（CGCG）相关。在大鼠垂体组织培养细胞系GH3的9个产生GH的亚克隆中，以及从大鼠垂体前叶分离的超过50%的DNA中，该ThaI位点未甲基化，垂体前叶包含产生GH的促生长激素细胞以及不产生GH的细胞。在从不产生GH的组织（如大鼠脾脏、肾脏、肝脏和大脑）制备的DNA中，该ThaI位点完全甲基化。此外，在GH3细胞与已消除GH产生的小鼠成纤维细胞融合形成的杂交细胞中，该位点也完全甲基化。在大鼠GH基因区域的其他10个限制性位点的DNA甲基化与GH3细胞产生GH的亚克隆以及不产生GH的GH3×LB82杂交细胞中的GH表达无关。我们认为，转录的GH基因RNA转录起始位点5'端144 bp处甲基化的保守缺失确定了一个潜在的GH基因控制区域。
