Bollag R J, Liskay R M
Department of Human Genetics, Yale University School of Medicine, New Haven, Connecticut 06510.
Genetics. 1988 May;119(1):161-9. doi: 10.1093/genetics/119.1.161.
Recombination in mammalian cells is thought to involve both reciprocal and nonreciprocal modes of exchange, although rigorous proof is lacking due to the inability to recover all products of an exchange. To investigate further the relationship between these modes of exchange, we have analyzed intrachromosomal recombination between duplicated herpes simplex virus thymidine kinase (HSV tk) mutant alleles arranged as inverted repeats in cultured mouse L cells. In crosses between inverted repeats, a single intrachromatid reciprocal exchange leads to inversion of the sequence between the crossover sites and recovery of both genes involved in the event. The majority of recombinant products do not display such inversion and are thus consistent with a nonreciprocal mode of recombination (gene conversion). The remaining products display the sequence inversion predicted for intrachromatid reciprocal exchange. In light of the fact that intrachromatid exchanges occur, the rarity of intrachromatid double reciprocal exchanges strengthens the interpretation that the majority of events in this and previous investigations involve gene conversion. Furthermore, in accord with prediction, one-third of the reciprocal recombinants (inversions) display associated gene conversion. This association suggests that reciprocal and nonreciprocal modes of exchange are mechanistically related in mammalian cells. Finally, the occurrence of inversion recombinants suggests that intrachromosomal recombination can be a conservative (nondestructive) process.
尽管由于无法获得交换的所有产物而缺乏确凿的证据，但哺乳动物细胞中的重组被认为涉及相互交换和非相互交换两种模式。为了进一步研究这些交换模式之间的关系，我们分析了在培养的小鼠L细胞中作为反向重复排列的重复单纯疱疹病毒胸苷激酶（HSV tk）突变等位基因之间的染色体内重组。在反向重复之间的杂交中，单个染色单体内相互交换导致交换位点之间的序列倒位，并恢复该事件中涉及的两个基因。大多数重组产物不显示这种倒位，因此与非相互重组模式（基因转换）一致。其余产物显示出染色单体内相互交换所预测的序列倒位。鉴于染色单体内交换的发生，染色单体内双相互交换的罕见性强化了这样的解释，即本次及之前研究中的大多数事件涉及基因转换。此外，与预测一致，三分之一的相互重组体（倒位）显示出相关的基因转换。这种关联表明，在哺乳动物细胞中，相互交换和非相互交换模式在机制上是相关的。最后，倒位重组体的出现表明染色体内重组可以是一个保守（非破坏性）的过程。
