PROXIMAL AND DISTAL EFFECTS OF SEQUENCE CONTEXT ON ULTRAVIOLET MUTATIONAL HOTSPOTS IN A SHUTTLE VECTOR REPLICATED IN XERODERMA CELLS
PROXIMAL AND DISTAL EFFECTS OF SEQUENCE CONTEXT ON ULTRAVIOLET MUTATIONAL HOTSPOTS IN A SHUTTLE VECTOR REPLICATED IN XERODERMA CELLS
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DOI：
10.1006/jmbi.1994.1160
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发表时间：
1994-02-18
影响因子：
5.6
通讯作者：
SEIDMAN, MM
中科院分区：
文献类型：
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作者：
PARRIS, CN;LEVY, DD;SEIDMAN, MM
热点是各种标记基因中由诱变剂诱导的突变谱的标准特征。虽然人们普遍认为序列背景对热点位置有重要影响，但直接的实验证据非常有限。我们研究了紫外线诱变的抑制tRNA市场基因（supF）进行哺乳动物穿梭载体和复制着色性干皮病细胞培养。我们现在已经构建了一个小家族的功能性变体抑制tRNA标记基因，它们彼此之间有一个或两个核苷酸的变化。对每个变异基因产生UV突变光谱。我们发现，从5′ TC到5′ CC的二嘧啶的变化消除了一个强的突变热点。此外，在upF基因中的单个碱基变化伴随着8个碱基之外的新热点的出现。最后，另一个单一的碱基变化抑制了48个碱基以外的主要热点。对UV修饰的标记基因进行聚合酶终止测定，用于测量光产物的频率和分布。热点模式的差异不能用修饰模式的差异来解释。这些结果表明，序列背景的变化可以直接影响特定位点的诱变概率。
Hotspots are a standard feature of mutational spectra induced by mutagens in a variety of marker genes. While it is generally believed that sequence context exerts an important influence on hotspot location, direct experimental evidence is quite limited. We have studied ultraviolet mutagenesis in a suppressor tRNA market gene (supF) carried in a mammalian shuttle vector and replicated in Xeroderma pigmentosum cells in culture. We have now constructed a small family of functional variant suppressor tRNA marker genes which differ from one another by one or two nucleotide changes. UV mutational spectra were generated for each variant gene. We found that the change of a dipyrimidine from 5′ TC to 5′ CC eliminated a strong mutational hotspot. In addition a single base change in thesupFgene was accompanied by the appearance of a new hotspot eight bases away. Finally, another single base change suppressed a major hotspot 48 bases away. Polymerase stop assays on the UV modified marker genes used to measure the frequency and distribution of photoproducts. The differences in hotspot patterns could not be explained by differences in modification patterns. These results indicate that a change in sequence context can directly influence the probability of mutagenesis at specific sites.