Polo-like kinase Cdc5 drives exit from pachytene during budding yeast meiosis

Abstract

In budding yeast, exit from the pachytene stage of meiosis requires the mid-meiosis transcription factor Ndt80, which promotes expression of ∼200 genes. Ndt80 is required for meiotic function of polo-like kinase (PLK, Cdc5) and cyclin-dependent kinase (CDK), two cell cycle kinases previously implicated in pachytene exit. We show that ongoing CDK activity is dispensable for two events that accompany exit from pachytene: crossover formation and synaptonemal complex breakdown. In contrast, CDC5 expression in ndt80⌬ mutants efficiently promotes both events. Thus, Cdc5 is the only member of the Ndt80 transcriptome required for this critical step in meiotic progression. During meiosis, a single round of DNA replication is followed by two successive divisions (meiosis I and meiosis II), producing four haploid gametes. This is achieved by segregation of homologs, homologous chromosomes of different parental origin, during meiosis I, followed by segregation of sister chromatids in meiosis II. During the prophase of meiosis I, progressive chromosome condensation is accompanied by homolog pairing and recombination, which culminate at the pachytene stage, where homologs are paired along their entire lengths and connected by the synaptonemal complex (SC). Upon exit from pachytene, the SC disappears and chromosomes become diffuse, only to recondense at diplotene/diakinesis as visible homologs connected by crossovers.Meiotic recombination initiates in early meiosis I prophase by the formation of DNA double-strand breaks (DSBs), catalyzed by the Spo11 endonuclease (Keeney and Neale 2006). As cells progress toward pachytene, DSBs are repaired to form either noncrossover (NCO) recombinants or joint molecule (JM) intermediates, many of which contain parental homologs connected by double Holliday junctions (Bishop and Zickler 2004). JMs are resolved, primarily as crossover recombinants (COs), at the end of pachytene. Crossovers provide the interhomolog connections that later ensure proper homolog alignment on the metaphase I spindle and thus their accurate segregation at anaphase I.The exit from pachytene is a crucial transition, since it is associated with the resolution of JMs as COs, SC disassembly, and kinetochore modification so that sister kinetochores orient toward the same spindle pole (monoorientation), and the separation of duplicated spindle pole bodies (SPBs), the fungal centrosome equivalents (Shuster and Byers 1989;Xu et al. 1995Xu et al. , 1997Clyne et al. 2003;Lee and Amon 2003b). Failure in any of these processes can result in chromosome nondisjunction and the production of aneuploid progeny. Consequently, checkpoint systems monitor synapsis and recombination and prevent exit from pachytene unless these processes are complete (Roeder and Bailis 2000).Ndt80, a transcription factor first expressed in late pachytene, is a central target of these checkpoint systems (Xu et al. 1995;Tung et al. 2000). Ndt80 activates expression of more than 200 genes at mid-meiosis, including those required for meiotic divisions and spor...

Local chromosome context is a major determinant of crossover pathway biochemistry during budding yeast meiosis

“…These slower-migrating species contain branched DNA molecules, as would be expected for unresolved joint molecules (D. M., unpublished observations). Steady state VDE-DSB and final NCO levels were similar in all strains ( Figure 3D, Figure 3figure supplement 1), indicating that resolvases do not act during the initial steps of DSB repair, and consistent with most meiotic NCOs forming by mechanisms that do not involve Holliday junction resolution (Allers and Lichten, 2001a;De Muyt et al, 2012;Sourirajan and Lichten, 2008;Zakharyevich et al, 2012).…”

“…Most of the remaining events are repaired by a meiosis-specific CO pathway, in which an ensemble of meiotic proteins, called the ZMM proteins, stabilize early recombination intermediates and promote their maturation into double Holliday junction joint molecules (Allers and Lichten, 2001a;Bö rner et al, 2004;Lynn et al, 2007;Schwacha and Kleckner, 1994). These ZMM-stabilized joint molecules (JMs) are subsequently resolved as COs (Sourirajan and Lichten, 2008) through the action of the MutLg complex, which contains the Mlh1, Mlh3, and Exo1 proteins (Argueso et al, 2004;Khazanehdari and Borts, 2000;Wang et al, 1999;Zakharyevich et al, 2010Zakharyevich et al, , 2012. MutLg does not appear to make significant contributions to mitotic COs (Ira et al, 2003).…”

Sporulation in the Budding Yeast Saccharomyces cerevisiae

“…Many of the chromosomal events of meiosis I, including introduction of double strand breaks, formation of recombination intermediates, and pairing of homologous chromosomes by the synaptonemal complex occur prior to NDT80 expression. However, resolution of recombination intermediates and dissolution of the synaptonemal complex require Ndt80-mediated transcription of the CDC5 kinase (Clyne et al 2003;Sourirajan and Lichten 2008). The checkpoint monitors the progress of meiotic recombination and inhibits the activity of Ndt80 if incomplete recombination products are present (Roeder and Bailis 2000).…”

Polo kinase Cdc5 is a central regulator of meiosis I

“…Cdc5 has been implicated in the execution of all three meiosis I-specific events. CDC5 is required for the resolution of double Holliday junctions during homologous recombination (7,8). Cdc5 also controls the co-orientation of sister chromatids by promoting the association of the monopolin complex with kinetochores (7, 9).…”