Sugano T, Uchida T, Yamaizumi M
Institute for Medical Genetics, Kumamoto University Medical School.
J Biochem. 1991 Oct;110(4):667-74. doi: 10.1093/oxfordjournals.jbchem.a123637.
A protein factor which corrects the defect in xeroderma pigmentosum cells belonging to complementation group A (XP-A cells) was detected in a cell extract prepared from calf thymus. The activity of this factor was measured as the amount of unscheduled DNA synthesis (UDS) reappearing in UV-irradiated XP-A cells after microinjection of the extract. The native molecular mass of this factor was estimated to be 80 kDa by gel-filtration and 25 kDa by glycerol gradient centrifugation. The activity was, however, recovered at a position corresponding to 43 kDa after renaturation on an SDS-PAGE gel. The isoelectric point was determined to be approximately 7.5 by measuring the activity after renaturation on an IEF gel. These values were obtained with a partially purified sample. A spot corresponding to these values was detected on two-dimensional gel electrophoresis with a highly purified sample recovered from an SDS-PAGE gel. The purified protein stimulated UDS specifically in the XP-A cells and endowed the cells with a normal level of UV-resistance. The XP-A cells injected with the factor also showed a normal level of UDS after treatment with either 4HAQO or psoralen plus UV-A. This factor (XP-A complementing factor; XP-ACF) may be involved in the repair of DNA damage induced by various agents.
在从小牛胸腺制备的细胞提取物中检测到一种能纠正A组互补型着色性干皮病细胞（XP - A细胞）缺陷的蛋白质因子。该因子的活性通过微量注射提取物后，紫外线照射的XP - A细胞中重新出现的非预定DNA合成（UDS）量来衡量。通过凝胶过滤法估计该因子的天然分子量为80 kDa，通过甘油梯度离心法估计为25 kDa。然而，在SDS - PAGE凝胶上复性后，其活性在对应于43 kDa的位置恢复。通过在IEF凝胶上复性后测量活性，确定其等电点约为7.5。这些值是用部分纯化的样品获得的。在用从SDS - PAGE凝胶回收的高度纯化样品进行二维凝胶电泳时，检测到了对应于这些值的一个斑点。纯化的蛋白质在XP - A细胞中特异性地刺激UDS，并赋予细胞正常水平的抗紫外线能力。注射了该因子的XP - A细胞在用4HAQO或补骨脂素加UV - A处理后也显示出正常水平的UDS。这种因子（XP - A互补因子；XP - ACF）可能参与了由各种试剂诱导的DNA损伤的修复。
