Homeostatic control of meiotic G2/prophase checkpoint function by Pch2 and Hop1

Abstract

17 Checkpoints cascades coordinate cell cycle progression with essential chromosomal 18 processes. During meiotic G2/prophase, recombination and chromosome synapsis are 19 monitored by what are considered distinct checkpoints [1-3]. In budding yeast, the AAA+ 20 ATPase Pch2 is thought to specifically promote cell cycle delay in response to synapsis defects 21 [4-6]. However, unperturbed pch2D cells are delayed in meiotic G2/prophase [6], suggesting 22 paradoxical roles for Pch2 in cell cycle progression. Here, we provide insight into the checkpoint 23 roles of Pch2 and its connection to Hop1, a HORMA domain-containing client protein. 24 Contrary to current understanding, we find that the Pch2-Hop1 module is crucial for 25 checkpoint function in response to both recombination and synapsis defects, thus revealing a 26 shared meiotic checkpoint cascade. Meiotic checkpoint responses are transduced by DNA 27 break-dependent phosphorylation of Hop1 [7, 8]. Based on our data and on the effect of Pch2 28 on HORMA topology [9-11], we propose that Pch2 promotes checkpoint proficiency by 29 catalyzing the availability of signaling-competent Hop1. Conversely, we demonstrate that Pch2 30 can act as a checkpoint silencer, also in the face of persistent DNA repair defects. We establish 31 a framework in which Pch2 and Hop1 form a homeostatic module that governs general meiotic 32 checkpoint function. We show that this module can -depending on the cellular context -fuel 33 or extinguish meiotic checkpoint function, which explains the contradictory roles of Pch2 in cell 34 cycle control. Within the meiotic checkpoint, the Pch2-Hop1 module thus operates analogous 35 to the Pch2/TRIP13-Mad2 module in the spindle assembly checkpoint that monitors 36 chromosome segregation [12-16]. 37 38 repair 40 41 Results and discussion 42 43 Feedback regulation between Hop1, Zip1 and Pch2 influences SC assembly 44 In G2/prophase of the meiotic program, double strand break (DSB) formation 45 recombinational repair, synapsis of homologous chromosomes is integrated with cell cycle 46 progression [17]. In budding yeast, Zip1-mediated Synaptonemal Complex (SC) assembly promotes 47 cell cycle progression by regulating chromosome-based checkpoint activity [18-20]. The 48 chromosome axis, of which Hop1 is a key component, forms the structural foundation for recruitment 49 of the SC [21]. The functionality of meiotic checkpoints that monitor recombination and synapsis is 50 linked to successful recombination and SC establishment, and the function of Pch2 is associated with 51 both Hop1 and Zip1: Hop1 is a client of Pch2 [22][23][24][25], and chromosomal association of Pch2 is tightly 52 linked to Zip1/SC establishment [5, 20, 23,[26][27][28][29]. To understand the wiring between these numerous 53 crucial events during meiotic G2/prophase and the role of Pch2 herein, we initially investigated SC 54 formation and its relation to Pch2, Hop1 and Zip1. 55 SC components, like Zip1, can form extrachromosomal aggregates known as polycomplexes 56 (PCs) [4]. Cells ...

Novel mechanistic insights into the role of Mer2 as the keystone of meiotic DNA break formation

“…We propose that Hop1 needs to be "opened" by the AAA+ ATPase Pch2 24,25 , which facilitates the binding of the HORMA domain to the closure motif of Red1 26 (Figure 4D, middle). This is in line with recent models that show there is a balance between Pch2 and Hop1 levels, and that Pch2 is both required for checkpoint establishment (loading open Hop1 onto the axis) and silencing (removing Hop1 from the axis in a Zip1 dependent fashion) [27][28][29] .…”

Chromosome-autonomous feedback downregulates meiotic DSB competence upon synaptonemal complex formation

“…Synapsis also displaces specialized assemblies of SPO11-accessory proteins REC114 and MEI4 that form on the pseudoautosomal region, the only part of the X and Y chromosomes that recombines in male meiosis (Acquaviva et al 2020). In yeast, the TRIP13 ortholog Pch2 also directs relocalization of Hop1 (ortholog of HORMAD1) after SC formation (Borner et al 2008;Joshi et al 2009;Subramanian et al 2016;Raina and Vader 2020). Moreover, many proteins that promote Spo11 activity (Mei4, Rec102, Rec104, Rec114, and Red1) all dissociate from synapsed chromosomes (Smith and Roeder 1997;Kee et al 2004;Li et al 2006;Maleki et al 2007;Panizza et al 2011;Carballo et al 2013).…”