Sequential steps in DNA replication are inhibited to ensure reduction of ploidy in meiosis

• DOI: 10.1091/mbc.e12-11-0825
• Publication Date: 2013-01-10T05:49:13Z
• Authors: Hui Hua; Mandana Namdar; Olivier Ganier; Juraj Gregan; Marcel Méchali; Stephen E. Kearsey
• Keywords: XENOPUS-OOCYTES; DNA Replication; 0301 basic medicine; BUDDING YEAST; Saccharomyces cerevisiae Proteins; HSK1 KINASE; Chromosomal Proteins, Non-Histone; FISSION YEAST; [SDV.GEN] Life Sciences [q-bio]/Genetics; Saccharomyces cerevisiae; S Phase; 03 medical and health sciences; CELL-CYCLE REGULATION; Chromosome Segregation; Phosphorylation; 106022 Mikrobiologie; 0303 health sciences; Ploidies; Articles; Chromatin; PHOSPHORYLATION SITES; DNA-Binding Proteins; Meiosis; S-PHASE; G(2)/M CHECKPOINT; 106022 Microbiology; RE-REPLICATION; CHROMOSOME SEGREGATION

Meiosis involves two successive rounds of chromosome segregation without an intervening S phase. Exit from meiosis I is distinct from mitotic exit, in that replication origins are not licensed by Mcm2-7 chromatin binding, but spindle disassembly occurs during a transient interphase-like state before meiosis II. The absence of licensing is assumed to explain the block to DNA replication, but this has not been formally tested. Here we attempt to subvert this block by expressing the licensing control factors Cdc18 and Cdt1 during the interval between meiotic nuclear divisions. Surprisingly, this leads only to a partial round of DNA replication, even when these factors are overexpressed and effect clear Mcm2-7 chromatin binding. Combining Cdc18 and Cdt1 expression with modulation of cyclin-dependent kinase activity, activation of Dbf4-dependent kinase, or deletion of the Spd1 inhibitor of ribonucleotide reductase has little additional effect on the extent of DNA replication. Single-molecule analysis indicates this partial round of replication results from inefficient progression of replication forks, and thus both initiation and elongation replication steps may be inhibited in late meiosis. In addition, DNA replication or damage during the meiosis I–II interval fails to arrest meiotic progress, suggesting absence of checkpoint regulation of meiosis II entry.