Abstract
DNA entanglements and supercoiling arise frequently during normal DNA metabolism. DNA topoisomerases are highly conserved enzymes that resolve the topological problems that these structures create. Topoisomerase II (TOPII) releases topological stress in DNA by removing DNA supercoils through breaking the two DNA strands, passing a DNA duplex through the break and religating the broken strands. TOPII performs key DNA metabolic roles essential for DNA replication, chromosome condensation, heterochromatin metabolism, telomere disentanglement, centromere decatenation, transmission of crossover (CO) interference, interlock resolution and chromosome segregation in several model organisms. In this study, we reveal the endogenous role of Arabidopsis thaliana TOPII in normal root growth and cell cycle, and mitotic DNA repair via homologous recombination. Additionally, we show that the protein is required for meiotic DSB repair progression, but not for CO formation. We propose that TOPII might promote mitotic HR DNA repair by relieving stress needed for HR strand invasion and D-loop formation.
Highlights
DNA topoisomerases are highly conserved enzymes that resolve topological problems that arise during a wide range of DNA metabolic processes including DNA replication, DNA transcription, DNA repair, chromosome condensation, heterochromatin metabolism, telomere disentanglement, centromere decatenation, chromosome remodelling and segregation and meiotic interlock disentanglement [1,2,3,4,5,6,7,8]
In the case of meiosis, we have described a role for Topoisomerase II (TOPII) in meiotic chromosome condensation and interlock resolution [7]
We investigate the role of TOPII in somatic and meiotic Homologous recombination (HR) DNA repair in the model organism Arabidopsis thaliana
Summary
DNA topoisomerases are highly conserved enzymes that resolve topological problems that arise during a wide range of DNA metabolic processes including DNA replication, DNA transcription, DNA repair, chromosome condensation, heterochromatin metabolism, telomere disentanglement, centromere decatenation, chromosome remodelling and segregation and meiotic interlock disentanglement [1,2,3,4,5,6,7,8] Resolution of these topological challenges is achieved via a common mechanism that involves single-strand (type I class, TOPI and TOP3) or double-strand (type II class, TOPII) cleavage of the DNA helix, and a strand-passing step that releases the tension [9]. We observe a delay in DSB repair during meiosis, though generally, normal meiotic recombination levels and CO patterning In light of these results, we propose a model in which TOPII would be needed to release tension created by HR DNA repair, by solving the positive supercoiling accumulated around those regions
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