Napolitano R L, Lambert I B, Fuchs R P
UPR Cancérogenèse et Mutagenèse Moléculaire et Structurale, CNRS, IBMC, Strasbourg, France.
Biochemistry. 1994 Feb 15;33(6):1311-5. doi: 10.1021/bi00172a004.
In order to examine the mechanisms of induced frameshift mutagenesis, we constructed double-stranded DNA plasmids which contain single N-2-acetylaminofluorene (AAF) adducts at specified positions within a run of contiguous guanine residues. The length of the homopolymeric run and the nature of the bases flanking the contiguous sequence were systematically varied. Monomodified plasmids were introduced into SOS-induced Escherichia coli, and -1 frameshift mutations were scored by means of a phenotypic assay. A strong positional effect of the DNA adduct within the contiguous sequence was observed irregardless of the nature of the flanking bases: the AAF-induced mutation frequency was 20-200-fold higher at the 3'-end of the contiguous sequence than at the 5'-end. In addition, for a given number of guanine residues flanking the GAAF adduct on its 5'-side, differences (up to 5-fold) in the induced mutation frequency were observed as a function of the base 3' to the adduct (CGGGAAFAT approximately CGGGAAFGT > CGGGAAFCT > CGGGAAFTT). These results are discussed, within the frame of an incorporation slippage model, in terms of differences in stability and occurrence of the slipped mutagenic intermediates.
为了研究诱导移码突变的机制，我们构建了双链DNA质粒，这些质粒在一串连续的鸟嘌呤残基内的特定位置含有单个N-2-乙酰氨基芴（AAF）加合物。同聚物链的长度以及相邻序列侧翼碱基的性质被系统地改变。将单修饰的质粒导入SOS诱导的大肠杆菌中，并通过表型分析对-1移码突变进行评分。无论侧翼碱基的性质如何，在连续序列中均观察到DNA加合物的强烈位置效应：在连续序列的3'端，AAF诱导的突变频率比5'端高20-200倍。此外，对于在其5'侧与GAAF加合物相邻的给定数量的鸟嘌呤残基，观察到诱导突变频率的差异（高达5倍）是加合物3'端碱基的函数（CGGGAAFAT≈CGGGAAFGT＞CGGGAAFCT＞CGGGAAFTT）。在掺入滑动模型的框架内，根据滑动诱变中间体的稳定性和出现的差异对这些结果进行了讨论。
