Nonaka M, Kimura H, Yeul Y D, Yokoyama S, Nakayama K, Takahashi M
Proc Natl Acad Sci U S A. 1986 Oct;83(20):7883-7. doi: 10.1073/pnas.83.20.7883.
To elucidate the molecular basis underlying the difference in the mode of gene expression between mouse complement C4 (constitutive) and sex-limited protein (Slp) (testosterone-regulated), we compared nucleotide sequences and transcriptional regulatory activities of the 5'-flanking regions of these two genes. Although the two sequences showed a high degree of overall homology (95%) up to 1.9 kilobases (kb) upstream from the transcription initiation site, the Slp sequence lacked a 31-nucleotide segment containing ACACCC repeats and a 60-nucleotide segment containing ACAC repeats, which are present, respectively, 1.6 kb and 200 base pairs (bp) upstream from the transcription initiation site of the C4 gene. When assayed in human hepatoma-derived HepG2 cells, the 1.8-kb 5'-flanking DNA fragment of the C4 gene demonstrated strong transcriptional activity, whereas the corresponding DNA fragment of the Slp gene showed only negligible activity. By progressive deletion experiments, it was shown that the difference in the constitutive transcriptional activity of the C4 and Slp genes was accounted for by the presence or absence of the positive regulatory domain located between 1700 bp and 400 bp upstream of the transcription initiation site.
为阐明小鼠补体C4（组成型）和性限制蛋白（Slp）（受睾酮调节）基因表达模式差异的分子基础，我们比较了这两个基因5'侧翼区的核苷酸序列和转录调控活性。尽管在转录起始位点上游1.9千碱基（kb）范围内，这两个序列显示出高度的总体同源性（95%），但Slp序列缺少一个包含ACACCC重复序列的31核苷酸片段和一个包含ACAC重复序列的60核苷酸片段，它们分别位于C4基因转录起始位点上游1.6 kb和200碱基对（bp）处。当在人肝癌来源的HepG2细胞中进行检测时，C4基因的1.8 kb 5'侧翼DNA片段表现出很强的转录活性，而Slp基因的相应DNA片段仅显示出可忽略不计的活性。通过逐步缺失实验表明，C4和Slp基因组成型转录活性的差异是由转录起始位点上游1700 bp至400 bp之间是否存在正调控域所致。
