Crossover recombination is essential for accurate chromosome segregation during meiosis. The MutSγ-complex, Msh4-Msh5, facilitates crossing over by binding and stabilizing nascent recombination intermediates. We show that these activities are governed by regulated proteolysis. MutSγ is initially inactive for crossing over due to an N-terminal degron on Msh4 that renders it unstable by directly targeting proteasomal degradation. Activation of MutSγ requires the Dbf4dependent kinase, Cdc7 (DDK), which directly phosphorylates and thereby neutralizes the Msh4 degron. Genetic requirements for Msh4 phosphorylation indicate that DDK targets MutSγ only after it has bound to nascent JMs in the context of synapsing chromosomes. Overexpression studies confirm that the steady-state level of Msh4, not phosphorylation perse, is the critical determinant for crossing over. At the DNA level, Msh4 phosphorylation enables the formation and crossover-biased resolution of double-Holliday Junction intermediates. Our study establishes regulated protein degradation as a fundamental mechanism underlying meiotic crossing over.

Soldiers who play video games to varying degrees were solicited to fill out a survey on dreams and gaming. A prescreening filtered out those who were not soldiers, who did not game and who were suffering from various psychological problems in the last six months. The remaining soldiers filled out these inventories; general and military demographics, history of video game play, Emotional Reactivity and Numbing Scale (ERNS), and a Trauma Inventory. They were then asked to provide two dreams, one recent and one that was impactful from their military service. Following the military dream they filled out Impactful Dreams Questionnaire (IDQ) about that dream only. Dream content analysis was conducted using threat simulation, war content and lucid/control/gaming content. High and low end frequency gamer groups were identified and compared on these dream content scales. Because the nightmare literature shows that affect load and distress are predictors of nightmare suffering. ERNS and Trauma history were covariates in the ANCOVA's on gamer group x dream type. It was found that the high end gaming group exhibited less threat and war content in their military dreams than the low end group.

The MutSγ complex, Msh4-Msh5, binds DNA joint-molecule (JM) intermediates during homologous recombination to promote crossing over and accurate chromosome segregation at the first division of meiosis. MutSγ facilitates the formation and biased resolution of crossoverspecific JM intermediates called double Holliday junctions. Here we show that these activities are governed by regulated proteasomal degradation. MutSγ is initially inactive for crossing over due to an N-terminal degron on Msh4 that renders it unstable. Activation of MutSγ requires the Dbf4-dependent kinase, Cdc7 (DDK), which directly phosphorylates and thereby neutralizes the Msh4 degron. Phosphorylated Msh4 is chromatin bound and requires DNA strand exchange and chromosome synapsis, implying that DDK specifically targets MutSγ that has already bound nascent JMs. Our study establishes regulated protein degradation as a fundamental mechanism underlying meiotic crossover control. the differentiation of crossover sites manifests as the selective retention and accumulation of specific recombination factors. One such factor is MutSγ, a heterodimer of Msh4 and Msh5, two homologs of the DNA mismatch-recognition factor MutS (Manhart and Alani, 2016;Snowden et al., 2004). Msh4 and Msh5 are members the ZMM proteins (Zip1, Zip2, Zip3, Zip4, Msh4, Msh5, Mer3, and Spo16), a diverse set of activities that facilitate crossover-specific events of recombination, and couple these events to chromosome synapsis (Fung et al., 2004;Hunter, 2015;Lynn et al., 2007;Shinohara et al., 2008). As seen in a variety of species, initial numbers of MutSγ immunostaining foci greatly outnumber final crossover numbers (De Muyt et al., 2014; de Vries et al., 1999;Edelmann et al., 1999;Higgins et al., 2008;Kneitz et al., 2000;Yokoo et al., 2012;Zhang et al., 2014). As prophase I progresses, MutSγ is lost from most recombination sites but retained at sites that will go on to mature into crossovers. This patterning process is dependent on the Zip3/RNF212/ZHP-3/HEI10 family of RING E3 ligases (Agarwal and Roeder, Wang et al., 2012;Yokoo et al., 2012;Zhang et al., 2018). Additional evidence implicates the SUMO-modification and ubiquitin-proteasome systems in meiotic crossover control (Ahuja et al., 2017; Rao et al., 2017) and suggests a model in which factors such as MutSγ are selectively stabilized at crossover sites by protecting them from proteolysis. Implicit in this model is the notion that MutSγ may be intrinsically unstable.Here, we show that regulated proteolysis plays a direct and essential role in meiotic crossing over. Msh4 is identified as an intrinsically unstable protein that is targeted for proteasomal degradation by an N-terminal degron thereby rendering MutSγ inactive for crossing over. Activation of MutSγ occurs by neutralizing the Msh4 degron via Cdc7-catalyzed phosphorylation. Thus, a key meiotic pro-crossover factor is activated by attenuating its proteolysis.

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