Network Rewiring of Homologous Recombination Enzymes during Mitotic Proliferation and Meiosis

Abstract

Summary Homologous recombination (HR) is essential for high-fidelity DNA repair during mitotic proliferation and meiosis. Yet, context-specific modifications must tailor the recombination machinery to avoid (mitosis) or enforce (meiosis) the formation of reciprocal exchanges—crossovers—between recombining chromosomes. To obtain molecular insight into how crossover control is achieved, we affinity purified 7 DNA-processing enzymes that channel HR intermediates into crossovers or noncrossovers from vegetative cells or cells undergoing meiosis. Using mass spectrometry, we provide a global characterization of their composition and reveal mitosis- and meiosis-specific modules in the interaction networks. Functional analyses of meiosis-specific interactors of MutLγ-Exo1 identified Rtk1, Caf120, and Chd1 as regulators of crossing-over. Chd1, which transiently associates with Exo1 at the prophase-to-metaphase I transition, enables the formation of MutLγ-dependent crossovers through its conserved ability to bind and displace nucleosomes. Thus, rewiring of the HR network, coupled to chromatin remodeling, promotes context-specific control of the recombination outcome.

Resolvases, Dissolvases, and Helicases in Homologous Recombination: Clearing the Road for Chromosome Segregation

“…Much less is known about the possible role of Mph1 during meiosis in S. cerevisiae. A recent comprehensive proteomics work aimed to discover the interaction profile of various DNA-processing enzymes involved in HR has revealed that the Mph1 protein interaction landscape is significantly reduced in meiotic versus mitotic cells [54]. Nevertheless, this study provides evidence for the existence of protein complexes including Mph1 and other genome integrity factors (Mhf1, Mhf2, and Mte1), as well as transcription factors (Fkh1, Fkh2) during meiotic prophase I.…”

“…In fact, recent work using return-to-growth (RTG) experiments has shown that the absence of Rmi1, but not that of Sgs1, prevents complete JM resolution leading to the activation of the Rad9-dependent DNA damage response [87]. Consistent with this notion, only a small fraction of the Top3-Rmi1 complex present in prophase I cells is stably associated with Sgs1 [54].…”

“…It has been proposed that the complex cooperates with Mus81-Mms4 and Yen1 in the alternative pathway that resolves ZMM-independent JMs that have also escaped Sgs1-dependent dissolution, although the contribution of Slx1-Slx4 appears to be minor [76,77] ( Figure 1). Like in mitotic cells, Rtt107 and Dbp11 have been identified in Slx1-Slx4 complex purifications from prophase I and metaphase I meiotic cells, suggesting that the physical interactions among Rtt107, Dbp11, and Slx1-Slx4 may have functional implications also during meiosis [54,155,157]. In addition, Slx4 appears to have also an Slx1-independent function in meiotic DSB formation and CO distribution especially in the proximity of centromeres [158].…”

“…In this regard, it has been shown that the meiosis-specific recombinase Dmc1 limits Srs2 function by inhibiting its ATP hydrolysis activity, thus preventing its translocation on Dmc1-bound ssDNA filaments and enhancing the formation of desired interhomolog CO recombination events [53]. Highlighting the relevance of Srs2 function in meiosis, a complex network of multiple protein interactors during meiotic prophase I, including factors involved in DNA and RNA metabolism, has been recently discovered [54]. Whether these novel Srs2-interacting proteins are related to the processing of recombinant joint molecules (JMs) remains to be established.…”

“…Interestingly, the Smc5/6-Mms21 complex is necessary for antagonizing recombination intermediates generated in meiosis by destabilizing early intermediates and resolving JMs, extending the role of this mechanism to the meiotic pathway [94][95][96]. In addition to SUMO-dependent regulation, it has been shown that Sgs1 might also be subjected to phosphorylation-dependent regulation during the prophase to metaphase I transition in meiotic cells, coincident with the induction of Cdc5 [54]. On the other hand, it has been established that Sgs1 phosphorylation by Mec1 promotes its binding to the FHA1 domain of Rad53, enhancing its phosphorylation in response to replicative stress [97].…”