Hop1 is a component of the meiosis-specific chromosome axis and belongs to the evolutionarily conserved family of HORMA domain proteins. Hop1 and its orthologs in higher eukaryotes are a major factor in promoting double-strand DNA break formation and inter-homolog recombination. In budding yeast and mammals they are also involved in a meiotic checkpoint kinase cascade monitoring the completion of double-strand DNA break repair. We used the fission yeast, Schizosaccharomyces pombe, which lacks a canonical synaptonemal complex to test whether Hop1 has a role beyond supporting the generation of double-strand DNA breaks and facilitating inter-homolog recombination events. We determined how mutants of homologous recombination factors genetically interact with hop1, studied the role(s) of the HORMA domain of Hop1, and characterized a bio-informatically predicted interactor of Hop1, Aho1 (SPAC688.03c). Our observations indicate that in fission yeast, Hop1 does require its HORMA domain to support wild-type levels of meiotic recombination and localization to meiotic chromatin. Furthermore, we show that hop1Δ only weakly interacts genetically with mutants of homologous recombination factors, and in fission yeast likely has no major role beyond break formation and promoting inter-homolog events. We speculate that after the evolutionary loss of the synaptonemal complex, Hop1 likely has become less important for modulating recombination outcome during meiosis in fission yeast, and that this led to a concurrent rewiring of genetic pathways controlling meiotic recombination.
Bibliographical noteWe are grateful to Shin-ichiro Hiraga, Franz Klein, Jürg Kohli, Walter W. Steiner, Matthew C. Whitby, and the National BioResource Project (NBRP) Japan for providing strains and/or plasmids, and to K.C. Chan, M. Roca, and D. Whyte for technical assistance. Kevin Corbett, Nancy Hollingsworth, Takashi Kubota, and Josef Loidl are thanked for critical reading of this manuscript. Microscopy was performed at the University of Aberdeen Microscopy & Histology facility (Kevin Mackenzie). This work was supported by the Biotechnology and Biological Sciences Research Council UK (BBSRC, Doctoral Training Grant BB/F016964/1), and the University of Aberdeen (College of Life Sciences and Medicine Start-up grant to AL).
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- Schizosaccharomyces pombe
- homologous recombination
- chromosome axis