Isolation of x-ray-inducible transcripts from radioresistant human melanoma cells.

Twelve x-ray-induced transcripts (xips), differentially expressed 8- to 230-fold in x-irradiated versus unirradiated radioresistant human melanoma (U1-Mel) cells, were isolated as cDNA clones (xip1 through xip12) after four rounds of differential hybridization. Northern analyses revealed rare, medium, and abundant xips, ranging in size from 1.2 to 10 kb. All transcripts were transiently expressed and induced by low, but not by high (> 600 cGy), doses of radiation. Three transcripts (xip4, -7, and -12) were induced only by ionizing radiation, and many (i.e., xip1, -2, -3, -5, -6, -8, -9, -10, and -11) were also induced by UV irradiation or phorbol 12-myristate 13-acetate. Heat shock did not induce any of the xips, but it decreased basal levels of xip4, -7, -11, and -12. Three xip cDNA clones were identified as encoding thymidine kinase, DT diaphorase, and tissue-type plasminogen activator. The remaining nine cDNA clones showed little homology to known genes. Three clones contained regions homologous to c-fes/fps protooncogene, recombination activating gene 1, or the human angiogenesis factor gene. X-ray-inducible genes may function in damaged cells to regulate DNA repair, apoptosis, mutagenesis, and carcinogenesis. IMAGES:

本数据集包含12个X射线诱导转录本（xips），在经X射线照射与未照射的抗辐射人黑色素瘤（U1-Mel）细胞中，其表达差异倍数为8至230倍。研究通过四轮差异杂交筛选，分离得到了对应的互补DNA（cDNA）克隆（xip1至xip12）。Northern印迹分析显示，xips的丰度可分为稀有、中等和丰富三类，转录本大小介于1.2至10千碱基对（kb）之间。所有转录本均为瞬时表达，且可被低剂量辐射诱导，但高剂量（>600厘戈瑞[cGy]）辐射无法诱导其表达。其中3个转录本（xip4、xip7和xip12）仅可被电离辐射诱导，另有多个转录本（即xip1、xip2、xip3、xip5、xip6、xip8、xip9、xip10及xip11）同时可被紫外线照射或佛波醇12-肉豆蔻酸酯13-乙酸酯诱导。热激处理无法诱导任何xips的表达，反而会降低xip4、xip7、xip11及xip12的基础表达水平。3个xip cDNA克隆被鉴定为分别编码胸腺嘧啶核苷激酶、DT黄递酶及组织型纤溶酶原激活剂。剩余9个cDNA克隆与已知基因的同源性极低。另有3个克隆包含与c-fes/fps原癌基因、重组激活基因1（RAG1）或人血管生成因子基因同源的区域。X射线诱导基因可能在受损细胞中发挥调控DNA修复、细胞凋亡、诱变作用及致癌作用的功能。图像：