Novel Attributes of Hed1 Affect Dynamics and Activity of the Rad51 Presynaptic Filament during Meiotic Recombination

Abstract

Background: Hed1 attenuates the activity of Rad51 during meiotic recombination to allow Dmc1-dependent formation of interhomolog crossovers. Results: Hed1 possesses DNA binding and self-association activities and stabilizes Rad51 presynaptic filament. Conclusion: DNA binding, Rad51 interaction, and self-association are essential for Hed1 function as a key regulator of meiotic recombination. Significance: Our results shed light on the mechanism of interhomolog bias in meiotic recombination.

Spontaneous self-segregation of Rad51 and Dmc1 DNA recombinases within mixed recombinase filaments

“…Therefore, as an alternative strategy, we used GFP-tagged Hed1 to detect to distribution of Rad51 with the mixed filaments. Genetic and biochemical data have demonstrated that Hed1 interacts specifically with Rad51 (15,39), and Hed1-GFP complements a hed1D strain, indicating that the fluorescent protein retains function (14). Consistent with these findings, we can readily detect Hed1-GFP binding to Rad51, but we are unable to detect any GFP-Hed1 association with Dmc1 ( Figure 2A) (40).…”

“…Despite these many commonalities, Dmc1 is the recombinase responsible for performing strand invasion during meiosis (13). In contrast, Rad51 is actively downregulated by Hed1-and Mek1-mediated inhibition of its interactions with Rad54, which is a cofactor that is required for Rad51 strand invasion activity (11,(14)(15)(16)(17). However, Rad51 is required for normal progression through meiosis and promotes Dmc1 foci formation, consistent with a role for Rad51 as a Dmc1 accessory factor (6,7,13,18).…”

The Logic and Mechanism of Homologous Recombination Partner Choice

“…Hed1 would exert its role as part of the quiescence complex that keeps the sister-associated end from undergoing synthesis-mediated extension and ensuing IS-dHJ formation, in collaboration with Rad51 (Kim et al, 2010; Figure 1A). A role for Hed1 at a later stage in recombination has also been suggested by Tsubouchi and colleagues (Busygina et al, 2012). Hed1 may also act earlier, in concert with Dmc1 (above).…”

“…For mitotic recombination, Rad51 activity is promoted by so-called “mediator proteins” (Krejci et al, 2012) which include essential Rad51 loading factors (Rad55/57) and the PCSS complex (Psy1, Csm2, Shu1, and Shu2), which is important but not essential for Rad51 activity (Ball et al, 2009; Krejci et al, 2012; Shor et al, 2005; Tao et al, 2012; Qing et al, 2011; Sasanuma et al, 2013). In meiosis, Rad51 strand exchange is directly and specifically inhibited by meiosis-specific factor Hed1 (Busygina et al, 2012; Tsubouchi and Roeder, 2006). Rad51 modulator roles for partner choice are addressed below.…”

OsDMC1 Is Not Required for Homologous Pairing in Rice Meiosis

“…ER is often eliminated by recombinationdependent pairing process. In budding yeast, the strand exchange capacity of Rad51 is shut down to facilitate Dmc1-mediated interhomolog recombination (Tsubouchi and Roeder, 2006;Busygina et al, 2012). Moreover, a dmc1 mutation increased unequal sister chromatid recombination (Grushcow et al, 1999;Thompson and Stahl, 1999).…”