The Third Exon of the Budding Yeast Meiotic Recombination Gene HOP2 Is Required for Calcium-dependent and Recombinase Dmc1-specific Stimulation of Homologous Strand Assimilation

• Published in: The Journal of biological chemistry Vol. 289; no. 26; pp. 18076 - 18086
• Main Authors: Chan, Yuen-Ling, Brown, M. Scott, Qin, Daoming, Handa, Naofumi, Bishop, Douglas K.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 27-06-2014; American Society for Biochemistry and Molecular Biology
• Subjects: Amino Acid Sequence; Base Sequence; Calcium; Calcium - metabolism; Cell Cycle Proteins - genetics; Cell Cycle Proteins - metabolism; Chromosomal Proteins, Non-Histone - genetics; Chromosomal Proteins, Non-Histone - metabolism; Dmc1; DNA and Chromosomes; DNA Recombination; DNA, Fungal - genetics; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; Exons; Homologous Recombination; Hop2-Mnd1 Complex; Introns; Meiosis; Molecular Sequence Data; Rad51; Rad51 Recombinase - genetics; Rad51 Recombinase - metabolism; Saccharomyces cerevisiae - cytology; Saccharomyces cerevisiae - enzymology; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins - genetics; Saccharomyces cerevisiae Proteins - metabolism; Yeast; Rad51; Hop2-Mnd1 Complex; Yeast; Calcium; Introns; Dmc1; Homologous Recombination; Meiosis; DNA Recombination
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.M114.558601

During meiosis in Saccharomyces cerevisiae, the HOP2 and MND1 genes are essential for recombination. A previous biochemical study has shown that budding yeast Hop2-Mnd1 stimulates the activity of the meiosis-specific strand exchange protein ScDmc1 only 3-fold, whereas analogous studies using mammalian homologs show >30-fold stimulation. The HOP2 gene was recently discovered to contain a second intron that lies near the 3′-end. We show that both HOP2 introns are efficiently spliced during meiosis, forming a predominant transcript that codes for a protein with a C-terminal sequence different from that of the previously studied version of the protein. Using the newly identified HOP2 open reading frame to direct synthesis of wild type Hop2 protein, we show that the Hop2-Mnd1 heterodimer stimulated Dmc1 D-loop activity up to 30-fold, similar to the activity of mammalian Hop2-Mnd1. ScHop2-Mnd1 stimulated ScDmc1 activity in the presence of physiological (micromolar) concentrations of Ca2+ ions, as long as Mg2+ was also present at physiological concentrations, leading us to hypothesize that ScDmc1 protomers bind both cations in the active Dmc1 filament. Co-factor requirements and order-of-addition experiments suggested that Hop2-Mnd1-mediated stimulation of Dmc1 involves a process that follows the formation of functional Dmc1-ssDNA filaments. In dramatic contrast to mammalian orthologs, the stimulatory activity of budding yeast Hop2-Mnd1 appeared to be specific to Dmc1; we observed no Hop2-Mnd1-mediated stimulation of the other budding yeast strand exchange protein Rad51. Together, these results support previous genetic experiments indicating that Hop2-Mnd1 specifically stimulates Dmc1 during meiotic recombination in budding yeast.
Background: The previously characterized version of the Saccharomyces cerevisiae recombination protein Hop2 was a mutant.
Results: Wild type Hop2-Mnd1 robustly stimulates the activity of the meiotic strand exchange protein Dmc1 but not that of the mitotic strand exchange protein Rad51.
Conclusion: Hop2-Mnd1 specifically activates Dmc1 at physiological concentrations of ATP/Mg2+/Ca2+.
Significance: Robust Dmc1 activity allows further reconstitution of meiotic recombination.