Multiple kinases inhibit origin licensing and helicase activation to ensure reductive cell division during meiosis

Meiotic cells undergo a single round of DNA replication followed by two rounds of chromosome segregation (the meiotic divisions) to produce haploid gametes. Both DNA replication and chromosome segregation are similarly regulated by CDK oscillations in mitotic cells. Yet how these two events are uncoupled between the meiotic divisions is unclear. Using Saccharomyces cerevisiae, we show that meiotic cells inhibit both helicase loading and helicase activation to prevent DNA replication between the meiotic divisions. CDK and the meiosis–specific kinase Ime2 cooperatively inhibit helicase loading, and their simultaneous inhibition allows inappropriate helicase reloading. Further analysis uncovered two previously unknown mechanisms by which Ime2 inhibits helicase loading. Finally, we show that CDK and the polo–like kinase Cdc5 trigger degradation of Sld2, an essential helicase–activation protein. Together, our data demonstrate that multiple kinases inhibit both helicase loading and activation between the meiotic divisions, thereby ensuring reductive cell division.


Sample-size estimation
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Replicates
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For each experiment in the paper, at least one biological replicate was performed. The plotted qPCR data was determined as the mean of three PCR (technical) replicates as stated in the methods.

Statistical reporting
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Group allocation
• Indicate how samples were allocated into experimental groups (in the case of clinical studies, please specify allocation to treatment method); if randomization was used, please also state if restricted randomization was applied • Indicate if masking was used during group allocation, data collection and/or data analysis Please outline where this information can be found within the submission (e.g., sections or figure legends), or explain why this information doesn't apply to your submission: Additional data files ("source data") • We encourage you to upload relevant additional data files, such as numerical data that are represented as a graph in a figure, or as a summary table • Where provided, these should be in the most useful format, and they can be uploaded as "Source data" files linked to a main figure or table • Include model definition files including the full list of parameters used For all qPCR data, the mean is represented by the height of the bar and error bars represent the standard deviation from three independent experiments, as stated in the methods. For Figure 4C, the inhibition ratio was calculated from three independent experiments. Again, the mean is represented by the height of the bar and error bars represent the standard deviation, as stated in the figure legend. For Figure 6E, the mean is represented by the height of the bar and error bars represent the standard deviation from three independent experiments. All raw data for the qPCRs and the bar graphs in Figure 4C and Figure 6E is provided in the source data files, as well as the mean and standard deviations. P-values were not calculated for the qPCR data because they would be misleading due to the precision of qPCR measurements. The small differences observed between samples were often statistically significant despite not being biologically significant. Instead, we focused on the size of the observed differences in our experiments, which we discuss in the text.
For all experiments in the paper, treated and untreated samples both in vitro and in vivo were handled and analyzed simultaneously (for example, Figure 3, Figure 4, Figure  5, Figure 6).
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