Lambert M W, Tsongalis G J, Lambert W C, Hang B, Parrish D D
Department of Laboratory Medicine and Pathology, UMDNJ-New Jersey Medical School, Newark 07103.
Mutat Res. 1992 Jan;273(1):57-71. doi: 10.1016/0921-8777(92)90050-d.
Cells from patients with the inherited disorder, Fanconi's anemia (FA), were analyzed for endonucleases which recognize DNA interstrand cross-links and monoadducts produced by psoralen plus UVA irradiation. Two chromatin-associated DNA endonuclease activities, defective in their ability to incise DNA-containing adducts produced by psoralen plus UVA light, have been identified and isolated in nuclei of FA cells. In FA complementation group A (FA-A) cells, one endonuclease activity, pI 4.6, which recognizes psoralen intercalation and interstrand cross-links, has 25% of the activity of the normal human endonuclease, pI 4.6, on 8-methoxypsoralen (8-MOP) plus UVA-damaged DNA. In FA complementation group B (FA-B) cells, a second endonuclease activity, pI 7.6, which recognizes psoralen monoadducts, has 50% and 55% of the activity, respectively, of the corresponding normal endonuclease on 8-MOP or angelicin plus UVA-damaged DNA. Kinetic analysis reveals that both the FA-A endonuclease activity, pI 4.6, and the FA-B endonuclease activity, pI 7.6, have decreased affinity for psoralen plus UVA-damaged DNA. Both the normal and FA endonucleases showed approximately a 2.5-fold increase in activity on psoralen plus UVA-damaged reconstituted nucleosomal DNA compared to damaged non-nucleosomal DNA, indicating that interaction of these FA endonucleases with nucleosomal DNA is not impaired. These deficiencies in two nuclear DNA endonuclease activities from FA-A and FA-B cells correlate with decreased levels of unscheduled DNA synthesis (UDS), in response to 8-MOP or angelicin plus UVA irradiation, in these cells in culture.
对患有遗传性疾病范可尼贫血（FA）的患者的细胞进行了分析，以检测识别DNA链间交联以及补骨脂素加紫外线A（UVA）照射产生的单加合物的核酸内切酶。已在FA细胞的细胞核中鉴定并分离出两种与染色质相关的DNA核酸内切酶活性，它们切割补骨脂素加UVA光产生的含加合物DNA的能力存在缺陷。在FA互补组A（FA-A）细胞中，一种核酸内切酶活性，即识别补骨脂素嵌入和链间交联的pI 4.6，在8-甲氧基补骨脂素（8-MOP）加UVA损伤的DNA上，其活性仅为正常人pI 4.6核酸内切酶活性的25%。在FA互补组B（FA-B）细胞中，另一种核酸内切酶活性，即识别补骨脂素单加合物的pI 7.6，在8-MOP或当归素加UVA损伤的DNA上，其活性分别为相应正常核酸内切酶活性的50%和55%。动力学分析表明，FA-A核酸内切酶活性（pI 4.6）和FA-B核酸内切酶活性（pI 7.6）对补骨脂素加UVA损伤的DNA的亲和力均降低。与损伤的非核小体DNA相比，正常和FA核酸内切酶在补骨脂素加UVA损伤的重组核小体DNA上的活性均增加了约2.5倍，这表明这些FA核酸内切酶与核小体DNA的相互作用未受损。FA-A和FA-B细胞中这两种核DNA核酸内切酶活性的缺陷与这些培养细胞中对8-MOP或当归素加UVA照射的非计划DNA合成（UDS）水平降低相关。
