Paulsson Johan, El Karoui Meriem, Lindell Monica, Hughes Diarmaid
Department of Systems Biology, Harvard University, Boston, MA, 02115, USA.
School of Biological Sciences, Institute of Cell Biology, The University of Edinburgh, Edinburgh, EH9 3JR, UK.
Mol Microbiol. 2017 Jun;104(5):752-760. doi: 10.1111/mmi.13661. Epub 2017 Mar 13.
Gene conversion, non-reciprocal transfer from one homologous sequence to another, is a major force in evolutionary dynamics, promoting co-evolution in gene families and maintaining similarities between repeated genes. However, the properties of the transfer - where it initiates, how far it proceeds and how the resulting conversion tracts are affected by mismatch repair - are not well understood. Here, we use the duplicate tuf genes in Salmonella as a quantitatively tractable model system for gene conversion. We selected for conversion in multiple different positions of tuf, and examined the resulting distributions of conversion tracts in mismatch repair-deficient and mismatch repair-proficient strains. A simple stochastic model accounting for the essential steps of conversion showed excellent agreement with the data for all selection points using the same value of the conversion processivity, which is the only kinetic parameter of the model. The analysis suggests that gene conversion effectively initiates uniformly at any position within a tuf gene, and proceeds with an effectively uniform conversion processivity in either direction limited by the bounds of the gene.
基因转换，即从一个同源序列到另一个同源序列的非相互转移，是进化动力学中的一股主要力量，促进基因家族的共同进化并维持重复基因之间的相似性。然而，这种转移的特性——起始位置、进行的距离以及错配修复如何影响最终的转换片段——目前还没有被很好地理解。在这里，我们将沙门氏菌中的重复tuf基因用作基因转换的一个可定量处理的模型系统。我们在tuf的多个不同位置选择进行转换，并检测了错配修复缺陷型和错配修复 proficient 型菌株中转换片段的最终分布情况。一个考虑了转换基本步骤的简单随机模型，使用相同的转换持续性值（该模型唯一的动力学参数），对所有选择点的数据都显示出了极佳的一致性。分析表明，基因转换在tuf基因内的任何位置都能有效地均匀起始，并在基因边界限制的任一方向上以有效均匀的转换持续性进行。
