The processive kinetics of gene conversion in bacteria

• Published in: Molecular microbiology 2017-06, Vol.104 (5), p.752-760
• Main Authors: Paulsson, Johan, El Karoui, Meriem, Lindell, Monica, Hughes, Diarmaid
• Format: Article
• Language: English
• Subjects: Bacteria; Bacteria - genetics; Bacterial Proteins - genetics; Biological Evolution; Conversion; DNA Mismatch Repair; DNA Repair; Evolutionary genetics; Gene Conversion; Gene duplication; Gene families; Genes; Genetic recombination; Homology; Kinetics; Microbiology; Mismatch repair; Models, Genetic; Mutation; Peptide Elongation Factor Tu - genetics; Repair; Salmonella; Salmonella - genetics; Stochastic models; Tuf gene; Yeast
• ISSN: 0950-382X; 1365-2958; 1365-2958
• DOI: 10.1111/mmi.13661

Summary 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. Gene conversion is a major force in evolutionary dynamics, promoting co‐evolution in gene families. However, the properties of conversion – where it initiates, how far it proceeds, and how the resulting conversion tracts are affected by mismatch repair – have not been quantified. Our analysis suggests that gene conversion can initiate uniformly at any position within a gene, and proceed with a high uniform processivity in either direction limited by the bounds of the gene.