Goncalves O, Drobetsky E, Meuth M
Mol Cell Biol. 1984 Sep;4(9):1792-9. doi: 10.1128/mcb.4.9.1792-1799.1984.
Mutants induced at the adenine phosphoribosyl transferase (aprt) locus by dTTP or dCTP pool imbalances were examined for alterations in genomic DNA sequences. No observable changes were detected by Southern blot analysis of most mutant DNAs, suggesting induction of base pair alterations or other events below our level of detection (approximately 30 base pairs). However, in a few strains (11 from a total collection of 125 mutant cell strains), we were able to localize these events to restriction endonuclease recognition sequences when the mutations resulted in the loss or gain of a particular site. The distribution of lost or gained sites in aprt-deficient mutants induced by the two types of pool imbalances clearly varied, with those occurring in a mutator strain with increased dCTP clustering at one end of the aprt gene. Mutants induced by dTTP also revealed novel events: multiple restriction site modifications in a small region of the aprt gene in one mutant and a small (approximately 50 base pairs) insertion or duplication of DNA sequences. As in previous studies, very few deletion or insertion mutants were detected at the aprt locus. The significance of these findings in terms of the known biochemical and genetic consequences of these pool imbalances is discussed.
研究了由dTTP或dCTP库失衡在腺嘌呤磷酸核糖转移酶（aprt）基因座诱导产生的突变体的基因组DNA序列变化。通过对大多数突变体DNA进行Southern印迹分析，未检测到可观察到的变化，这表明诱导产生的是碱基对改变或其他低于我们检测水平（约30个碱基对）的事件。然而，在少数菌株中（总共125个突变细胞株中有11个），当突变导致特定位点的丢失或获得时，我们能够将这些事件定位到限制性内切酶识别序列。由两种类型的库失衡诱导产生的aprt缺陷型突变体中，丢失或获得位点的分布明显不同，在dCTP增加的突变菌株中发生的那些位点聚集在aprt基因的一端。由dTTP诱导产生的突变体还揭示了新的事件：一个突变体中aprt基因的一个小区域内有多个限制性位点修饰，以及一小段（约50个碱基对）DNA序列的插入或重复。与之前的研究一样，在aprt基因座检测到的缺失或插入突变体非常少。本文讨论了这些发现对于这些库失衡已知的生化和遗传后果的意义。
