Different functions for the domains of the Arabidopsis thaliana RMI1 protein in DNA cross-link repair, somatic and meiotic recombination

Simone Bonnet,Alexander Knoll,Holger Puchta,Frank Hartung

doi:10.1093/nar/gkt730

Simone Bonnet, Alexander Knoll + Show 2 more

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Journal: Nucleic Acids Research	Publication Date: Aug 16, 2013
Citations: 29	License type: CC BY 3.0

Affiliation: Karlsruhe Institute of Technology

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Recombination intermediates, such as double Holliday junctions, can be resolved by nucleases or dissolved by the combined action of a DNA helicase and a topoisomerase. In eukaryotes, dissolution is mediated by the RTR complex consisting of a RecQ helicase, a type IA topoisomerase and the structural protein RecQ-mediated genome instability 1 (RMI1). Throughout eukaryotes, the RTR complex is involved in DNA repair and in the suppression of homologous recombination (HR) in somatic cells. Surprisingly, Arabidopsis thaliana mutants of topoisomerase 3α and RMI1 are also sterile due to extensive chromosome breakage in meiosis I, indicating that both proteins are essential for meiotic recombination in plants. AtRMI1 harbours an N-terminal DUF1767 domain and two oligosaccharide binding (OB)-fold domains. To define specific roles for these individual domains, we performed complementation experiments on Atrmi1 mutants with an AtRMI1 full-length open reading frame (ORF) or deletion constructs lacking specific domains. We show that the DUF1767 domain and the OB-fold domain 1 are both essential for the function of AtRMI1 in DNA cross-link repair as well as meiotic recombination, but partially dispensable for somatic HR suppression. The OB-fold domain 2 is not necessary for either somatic or meiotic HR, but it seems to have a minor function in DNA cross-link repair.

Highlights

The resolution of recombination intermediates, such as double Holliday junctions, by endonucleases is an indispensable step for the proper segregation of homologous chromosomes in meiosis and to ensure genomic stability in somatic cells
We show that the domain of unknown function 1767 (DUF1767) domain and the oligosaccharide binding (OB)-fold domain 1 are both essential for the function of AtRMI1 in DNA cross-link repair as well as meiotic recombination, but partially dispensable for somatic homologous recombination (HR) suppression
Our results demonstrate that both the DUF1767 domain and the oligosaccharide binding-fold (OB-fold) domain 1 of the N-terminal part of AtRMI1 are necessary for the function of AtRMI1 in DNA repair

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Introduction

The resolution of recombination intermediates, such as double Holliday junctions (dHJ), by endonucleases is an indispensable step for the proper segregation of homologous chromosomes in meiosis and to ensure genomic stability in somatic cells. The dissolution mechanism by the RTR complex is an alternative way to process recombination intermediates, such as dHJs [1,2]. This mechanism was postulated first by Thaler and Stahl in 1988 [3] and requires a RecQ family DNA helicase and a type I topoisomerase. In contrast to TOP1 and 2, which are well-characterized and involved in DNA replication (TOP1, type IB) or decatenation of linked chromosomes (TOP2, type IIA) [9], the main function of yeast TOP3 is in the dissolution reaction of DNA double-strand break repair by homologous recombination (HR) [10,11,12]

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