Piazza L, Masch J, Feingold J, Mendez F, Maio J, Bases R
Radiat Res. 1987 Aug;111(2):254-66.
Expression of the prokaryotic gene for chloramphenicol acetyltransferase (EC 2.3.1.28) (CAT) in primate cells transfected with X-irradiated plasmid pSV2CAT was determined in transient expression assays. CAT expression did not depend upon the presence of supercoiled plasmids, but relaxed circular forms were essential. X-ray conversion of relaxed circles to linear forms paralleled the loss of CAT expression, with identical D0's in the first part of dose-response curves. X-ray-induced loss of supercoiled forms was complete at much lower doses. The D0 for inactivation of CAT expression by X irradiation of the plasmids in 1 mM Tris buffer was 270 Gy; it was 13 Gy for plasmids irradiated in water. The D0's for conversion of pSV2CAT to relaxed circle forms were only one-seventh as large as the D0's for CAT inactivation after X-ray in water or in 1 mM Tris buffer. Expression of the CAT gene in some representative repair-deficient human fibroblasts transfected with X-irradiated pSV2CAT was less than in monkey CV-1 cells or cell lines from normal human subjects. These results demonstrate a novel means to study low levels of X-ray damage in DNA correlating specific X-ray damage in the DNA with expression of the gene in unirradiated primate cells.
在瞬时表达试验中，测定了用X射线照射的质粒pSV2CAT转染的灵长类细胞中氯霉素乙酰转移酶（EC 2.3.1.28）（CAT）原核基因的表达。CAT表达不依赖于超螺旋质粒的存在，但松弛的环状形式是必不可少的。松弛环向线性形式的X射线转化与CAT表达的丧失平行，在剂量反应曲线的第一部分具有相同的D0值。X射线诱导的超螺旋形式的丧失在低得多的剂量下就已完成。在1 mM Tris缓冲液中，用X射线照射质粒使CAT表达失活的D0为270 Gy；在水中照射质粒时，D0为1十三条。pSV2CAT转化为松弛环状形式的D0仅为在水中或1 mM Tris缓冲液中X射线照射后CAT失活D0的七分之一。用X射线照射的pSV2CAT转染的一些代表性的DNA修复缺陷型人成纤维细胞中CAT基因的表达低于猴CV-1细胞或正常人的细胞系。这些结果证明了一种研究DNA中低水平X射线损伤的新方法，即将DNA中的特定X射线损伤与未照射的灵长类细胞中的基因表达相关联。
