Vos J M, Wauthier E L
Lineberger Comprehensive Cancer Research Center, University of North Carolina School of Medicine, Chapel Hill 27599-7295.
Mol Cell Biol. 1991 Apr;11(4):2245-52. doi: 10.1128/mcb.11.4.2245-2252.1991.
We have developed a general quantitative method for comparing the levels of drug-induced DNA crosslinking in specific mammalian genes. We observed a dramatic difference between the efficiency of the removal of both psoralen monoadducts and interstrand crosslinks from the rRNA genes and the efficiency of their removal from the dihydrofolate reductase (DHFR) gene in cultured human and hamster cells. While 90% of the interstand crosslinks were removed from the human DHFR gene in 48 h, less than 25% repair occurred in the rRNA genes. Similarly, in Chinese hamster ovary cells, 85% repair of interstrand crosslinks occurred within 8 h in the DHFR gene versus only 20% repair in the rRNA genes. The preferential repair of the DHFR gene relative to that of the rRNA genes was also observed for psoralen monoadducts in cells from both mammalian species. In human-mouse hybrid cells, the active mouse rRNA genes were five times more susceptible to psoralen modification than are the silent rRNA human genes, but adduct removal was similarly inefficient for both classes. We conclude that the repair of chemical damage such as psoralen photoadducts in an expressed mammalian gene may depend upon the class of transcription to which it belongs.
我们已经开发出一种通用的定量方法，用于比较特定哺乳动物基因中药物诱导的DNA交联水平。我们观察到，在培养的人类和仓鼠细胞中，从rRNA基因中去除补骨脂素单加合物和链间交联的效率与从二氢叶酸还原酶（DHFR）基因中去除它们的效率之间存在显著差异。虽然在48小时内，90%的链间交联从人类DHFR基因中被去除，但rRNA基因中的修复率不到25%。同样，在中国仓鼠卵巢细胞中，DHFR基因在8小时内链间交联的修复率为85%，而rRNA基因中只有20%的修复。在这两种哺乳动物细胞中，相对于rRNA基因，DHFR基因对补骨脂素单加合物的修复也具有优先性。在人-鼠杂交细胞中，活跃的小鼠rRNA基因对补骨脂素修饰的敏感性是沉默的人类rRNA基因的五倍，但两类基因的加合物去除效率同样低下。我们得出结论，在表达的哺乳动物基因中，诸如补骨脂素光加合物之类的化学损伤修复可能取决于其所属的转录类别。
