Mellon I, Spivak G, Hanawalt P C
Department of Biological Sciences, Stanford University, California 94305-5020.
Cell. 1987 Oct 23;51(2):241-9. doi: 10.1016/0092-8674(87)90151-6.
We find a dramatic difference in the efficiency of removal of UV-induced pyrimidine dimers from the transcribed and nontranscribed strands of the dihydrofolate reductase (DHFR) gene in cultured hamster and human cells. In hamster cells, 80% of the dimers are removed from the transcribed strand in 4 hr, but little repair occurs in the nontranscribed strand even after 24 hr. In human cells, repair is significantly faster in the transcribed strand than in the other strand. Furthermore, in the 5' flanking region of the human DHFR gene, selective rapid repair occurs in the opposite DNA strand relative to the transcribed strand of the DHFR gene. This strand is thought to serve as a template for transcription of a divergent transcript. These results have important implications for excision repair pathways and mutagenesis in mammalian cells.
我们发现，在培养的仓鼠和人类细胞中，二氢叶酸还原酶（DHFR）基因转录链和非转录链上紫外线诱导的嘧啶二聚体的去除效率存在显著差异。在仓鼠细胞中，80%的二聚体在4小时内从转录链上被去除，但即使在24小时后，非转录链上也几乎没有修复发生。在人类细胞中，转录链的修复明显比另一条链快。此外，在人类DHFR基因的5'侧翼区域，相对于DHFR基因转录链的相反DNA链上发生了选择性快速修复。这条链被认为是一个不同转录本转录的模板。这些结果对哺乳动物细胞中的切除修复途径和诱变具有重要意义。
