An enzyme-catalyzed multistep DNA refolding mechanism in hairpin telomere formation.
Publication Type:Journal Article
Source:PLoS Biol, Volume 11, Issue 1, p.e1001472 (2013)
Keywords:Agrobacterium tumefaciens, Bacterial Proteins, Chromosomes, Bacterial, Crystallography, X-Ray, DNA Replication, DNA Replication Timing, DNA, Bacterial, DNA-Binding Proteins, Gene Rearrangement, Nucleic Acid Conformation, Telomere
<p>Hairpin telomeres of bacterial linear chromosomes are generated by a DNA cutting-rejoining enzyme protelomerase. Protelomerase resolves a concatenated dimer of chromosomes as the last step of chromosome replication, converting a palindromic DNA sequence at the junctions between chromosomes into covalently closed hairpins. The mechanism by which protelomerase transforms a duplex DNA substrate into the hairpin telomeres remains largely unknown. We report here a series of crystal structures of the protelomerase TelA bound to DNA that represent distinct stages along the reaction pathway. The structures suggest that TelA converts a linear duplex substrate into hairpin turns via a transient strand-refolding intermediate that involves DNA-base flipping and wobble base-pairs. The extremely compact di-nucleotide hairpin structure of the product is fully stabilized by TelA prior to strand ligation, which drives the reaction to completion. The enzyme-catalyzed, multistep strand refolding is a novel mechanism in DNA rearrangement reactions.</p>