Hariharan P V, Remsen J F, Cerutti P A
Basic Life Sci. 1975;5A:51-9. doi: 10.1007/978-1-4684-2895-7_8.
The selective excision of products of the 5,6-dihydroxy-dihydrothymine type (t') from gamma-irradiated or OSO4-oxidized DNA or synthetic poly[d(A-T)] was observed with crude extracts of Escherichia coli and isolated nuclei from human carcinoma HeLa S-3 and Chinese hamster ovary cells. The results with E. coli extracts allow the following conclusion: (1) The uvrA-gene product is not required for t' excision. (2) Radiation-induced strand breakage is not required for product excision. (3) Experiments with extracts of E. coli polAexl showed that the 5' in equilibrium 3' exonuclease associated with polymerase I is responsible for the removal of t'. (4) Experiments with extracts of E. coli endo I lig 4 and the ligase inhibitor nicotinamide mononucleotide showed that polynucleotide ligase accomplishes the last strand resealing step in the excision-repair of t'. Isolated nuclei from HeLa and Chinese hamster ovary cells possess the necessary enzymes for the selective excision of t' from gamma-irradiated or osmium tetroxide oxidized DNA. Approximately 25 to 35% of the products were removed from DNA within 60 min. Unspecific DNA degradation was very low. Radiation-induced strand breakage is not required for product removal.
在大肠杆菌的粗提物以及源自人宫颈癌HeLa S-3细胞和中国仓鼠卵巢细胞的分离细胞核中，观察到了从经γ射线照射或经四氧化锇氧化的DNA或合成的聚[d(A-T)]中选择性切除5,6-二羟基-二氢胸腺嘧啶类型（t'）产物的现象。大肠杆菌提取物的实验得出以下结论：（1）切除t'不需要uvrA基因产物。（2）切除产物不需要辐射诱导的链断裂。（3）用大肠杆菌polAexl提取物进行的实验表明，与聚合酶I相关的5'平衡3'核酸外切酶负责去除t'。（4）用大肠杆菌内切酶I lig 4提取物和连接酶抑制剂烟酰胺单核苷酸进行的实验表明，多核苷酸连接酶完成了t'切除修复中的最后链重封步骤。HeLa细胞和中国仓鼠卵巢细胞的分离细胞核拥有从经γ射线照射或经四氧化锇氧化的DNA中选择性切除t'所需的酶。在60分钟内，约25%至35%的产物从DNA中被去除。非特异性DNA降解非常低。切除产物不需要辐射诱导的链断裂。
