MOLECULAR BIOLOGY OF CELLULAR INJURY

几个可诱导的DNA修复基因已经被很好地描述了 在原核系统中；在包括哺乳动物细胞在内的真核生物中， 越来越多的证据表明，类似的事件可能正在发生。 最近，我们已经证明了杂交减法可以 用于丰富仅由多个 特殊的细胞处理，如热休克。中国仓鼠 用紫外线照射细胞，从细胞中合成c DNA。 这些细胞的多腺苷化(PolyA)RNA。这个“UV”的cDNA是 与来自未照射细胞的Polya RNA杂交，并 分离到非杂交的基因片段。通过这种方法，UV- 诱导序列被浓缩了30倍以上。有了这个 扩增后，构建了cDNA文库。50种不同的 分离到的cdna克隆被发现编码 紫外线照射后，转录本诱导2~30倍。27种不同的基因 对克隆进行了测序，仅鉴定出金属硫蛋白 GenBank数据库表明，其中大多数 以前还没有分离出序列。在预赛中 实验中，发现其中几个克隆与 紫外线诱导的人成纤维细胞转录本。在中国仓鼠 体细胞突变体被选中以提高对DNA的敏感性 I·希克森的破坏因子，两种情况下的几个例子都增加了 并发现突变细胞中转录水平降低。这个 这些克隆序列的功能尚不清楚，但很可能 这些转录本中至少有一部分的蛋白质产物 在细胞对紫外线损伤的反应中发挥作用。

Several inducible DNA repair genes have been well characterized in prokaryotic systems; in eukaryotes including mammalian cells, there is increasing evidence that similar events may be occurring. Recently, we have shown that hybridization subtraction can be used to enrich for sequences induced only several fold by a particular cell treatment such as heat shock. Chinese hamster cells were UV-irradiated and cDNA was synthesized from the polyadenylated (polyA) RNA of these cells. This "UV" cDNA was hybridized with polyA RNA from unirradiated cells and the nonhybridizing cDNA was isolated. With this approach, UV- induced sequences were enriched for over 30 fold. With this enriched cDNA, a cDNA library was constructed. 50 different cDNA clones were isolated which were found to code for transcripts induced 2 to 30 fold after UV. 27 different cDNA clones were sequenced and only metallothionein was identified in the GenBank database which indicates that most of these sequences have not been isolated before. In preliminary experiments, several of these clones were found to hybridize to UV-inducible transcripts in human fibroblasts. In Chinese hamster somatic cell mutants selected for increased sensitivity to DNA damaging agents by I. Hickson, several examples of both increased and decreased transcription in the mutant cells were found. The function of these cloned sequences is unknown, but it is probable that the protein products of at least some of these transcripts play a role in the cellular response to UV damage.