The archaeal Xpf/Mus81/FANCM homolog Hef and the Holliday junction resolvase Hjc define alternative pathways that are essential for cell viability in Haloferax volcanii |
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| Authors: | Roxane Lestini Zhenhong Duan Thorsten Allers |
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| Institution: | 1. Department of Chemical Engineering, National Chung Hsing University, 250 Kuo Kuang Road, Taichung, 40227, Taiwan, ROC;2. Biotechnology Center, National Chung Hsing University, 250 Kuo Kuang Road, Taichung, 40227, Taiwan, ROC;1. Department of Physiology, Anatomy & Microbiology, La Trobe University, Melbourne, Victoria, Australia;2. Murdoch Childrens Research Institute, Royal Children’s Hospital, Melbourne, Victoria, Australia;1. Kavli Institute of Nanoscience, Department of Bionanoscience, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, the Netherlands;2. Genetics and Experimental Bioinformatics, Faculty of Biology, University of Freiburg, Schänzlestraße 1, 79104 Freiburg, Germany;3. Freiburg Institute for Advanced Studies, University of Freiburg, Albertstr. 19, 79104 Freiburg, Germany;4. Laboratory of Microbiology, Wageningen University, Stippeneng 4, 6708 WE Wageningen, the Netherlands;1. Marine Science & Technology Institute, College of Environmental Science and Engineering, Yangzhou University, China;2. Guangling College, Yangzhou University, China;3. Beijing Synchrotron Radiation Facility, Institute of High Energy Physics, Chinese Academy of Sciences, China;4. Univ Lyon, INSA De Lyon, CNRS UMR 5240, Lyon, France |
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| Abstract: | The XPF/MUS81 family of endonucleases is found in eukaryotes and archaea, in the former they play a critical role in DNA repair and replication fork restart. Hef is a XPF/MUS81 family member found in Euryarchaea and is related to the Fanconi anemia protein FANCM. We have studied the role of Hef in the euryarchaeon Haloferax volcanii. Unlike Xpf in eukaryotes, Hef is not involved in nucleotide excision repair; instead, this function is encoded by the uvrABC genes. Similarly, deletion of hef confers only moderate sensitivity to DNA crosslinking agents, whereas mutation of FANCM in leads to hypersensitivity in eukaryotes. However, Hef is essential for cell viability when the Holliday junction resolvase Hjc is absent, and both the helicase and nuclease activities of Hef are indispensable. By contrast, single mutants of hjc and hef display no significant defects in growth or homologous recombination. This suggests that Hef and Hjc are redundant for the resolution of recombination intermediates, and that Hef is the functional homolog of eukaryotic Mus81. Furthermore, deletion of hef in a recombination-deficient ΔradA background is highly deleterious but deletion of hjc has no effect. Therefore, Hjc acts exclusively in homologous recombination whereas Hef, in addition to its role in resolving recombination intermediates, can act in a pathway that avoids the use of homologous recombination. We propose that Hef and Hjc provide alternative means to restart stalled DNA replication forks. |
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