Collins A R, Johnson R T
J Cell Physiol. 1979 Apr;99(1):125-37. doi: 10.1002/jcp.1040990114.
Cultured cells of Microtus agrestis, the common field vole, perform unscheduled DNA synthesis after UV irradiation. They respond to incubation with a DNA synthesis inhibitor (1-beta-D-arabinofuranosylcytosine) following UV in ways typical of cells capable of excision repair, with reduced survival and an accumulation of breaks in pre-existing DNA. Microtus cells irradiated with UV in a quiescent pre-S-phase state are more sensitive to UV than are proliferating cells, in terms of survival. Adding DNA precursors (deoxyribonucleosides), and--in case of proliferating cells--growing in complete rather than dialysed serum, enhance UV survival. Quiescent cells show a higher rate of endonucleolytic incision of DNA after UV than do proliferating cells. The balance between incision (producing single-strand DNA breaks) and repair DNA synthesis (leading to rejoining of breaks) is shifted by the addition of deoxyribonucleosides, which suggests that DNA precursor supply is a rate-limiting factor in repair. The lower survival of quiescent cells (in the absence of added deoxyribonucleosides) may be due to insufficient precursor supply to meet the demands of the high incision rate.
普通田鼠（Microtus agrestis）的培养细胞在紫外线照射后会进行非预定DNA合成。紫外线照射后，它们与能够进行切除修复的细胞一样，对DNA合成抑制剂（1-β-D-阿拉伯呋喃糖基胞嘧啶）的孵育有反应，存活率降低，且原有DNA中的断裂处会积累。就存活率而言，处于静止前期S期状态的田鼠细胞经紫外线照射后比增殖细胞对紫外线更敏感。添加DNA前体（脱氧核糖核苷），以及对于增殖细胞而言，在完全血清而非透析血清中生长，可提高紫外线存活率。静止细胞经紫外线照射后DNA的内切核酸酶切割速率高于增殖细胞。添加脱氧核糖核苷会改变切割（产生单链DNA断裂）和修复DNA合成（导致断裂重新连接）之间的平衡，这表明DNA前体供应是修复过程中的一个限速因素。静止细胞（在未添加脱氧核糖核苷的情况下）存活率较低可能是由于前体供应不足，无法满足高切割速率的需求。
