Matroule J Y, Collet M, Boiteux S, Piette J
Laboratory of Virology, Institute of Pathology B23, University of Liège, Belgium.
J Photochem Photobiol B. 1997 Nov;41(1-2):36-44. doi: 10.1016/s1011-1344(97)00078-x.
A psoralen in which intracyclic oxygen atoms were replaced by sulfur (7H-thieno [3,2-g]-[1]-[benzothiopyran-7-one) [PSO(S-S)]) was recently synthesized and its photobiological properties were investigated. M13mp19 DNA photosensitization mediated by PSO (S-S) followed by transfection into competent E. coli gave rise to a very low phage progeny showing the high aptitude of this compound to modify DNA. In order to characterize the role of oxidative damages in the photosensitized reaction mediated by PSO(S-S), plasmid bearing the gene encoding the formamidopyrimidine DNA glycosylase (Fpg) under the control of the inducible lac Z promoter was transfected in E. coli. Overexpression of Fpg was induced by addition of isopropyl-beta-D-thio-galactopyranoside (IPTG) to the cells and monitored by western blot analysis. Fpg overexpression did not influence the rate of M13mp19 DNA photoinactivation by PSO(S-S) neither the mutation frequency measured by the expression of beta-galactosidase encoded by the lac Z gene beared by M13mp19. Analysis of the mutation patterns recorded with or without Fpg overexpression showed that several G to T transversions due to oxidative damages were repaired by Fpg. These data show that oxidative DNA damages generated during PSO(S-S) photosensitization have only limited biological implications measured in terms of DNA photoinactivation.
一种内环氧原子被硫取代的补骨脂素（7H-噻吩并[3,2-g]-[1]-[苯并噻喃-7-酮）[PSO(S-S)]）最近被合成，并对其光生物学性质进行了研究。PSO(S-S)介导的M13mp19 DNA光致敏作用，随后转染到感受态大肠杆菌中，产生了非常低的噬菌体后代，表明该化合物具有很高的修饰DNA的能力。为了表征氧化损伤在PSO(S-S)介导的光致敏反应中的作用，将携带在可诱导的lac Z启动子控制下编码甲酰胺嘧啶DNA糖基化酶（Fpg）的基因的质粒转染到大肠杆菌中。通过向细胞中添加异丙基-β-D-硫代半乳糖苷（IPTG）诱导Fpg的过表达，并通过蛋白质免疫印迹分析进行监测。Fpg的过表达既不影响PSO(S-S)对M13mp19 DNA的光灭活速率，也不影响由M13mp19携带的lac Z基因编码的β-半乳糖苷酶表达所测量的突变频率。对有或没有Fpg过表达时记录的突变模式的分析表明，Fpg修复了一些由氧化损伤导致的G到T颠换。这些数据表明，在PSO(S-S)光致敏过程中产生的氧化性DNA损伤，就DNA光灭活而言，其生物学意义有限。
