Abstract
Protein Phosphatase 2A (PP2A) is a heterotrimer composed of scaffolding (A), catalytic (C), and regulatory (B) subunits. PP2A complexes with B56 subunits are targeted by Shugoshin and BUBR1 to protect centromeric cohesion and stabilise kinetochore-microtubule attachments in yeast and mouse meiosis. In Caenorhabditis elegans, the closest BUBR1 orthologue lacks the B56-interaction domain and Shugoshin is not required for meiotic segregation. Therefore, the role of PP2A in C. elegans female meiosis is unknown. We report that PP2A is essential for meiotic spindle assembly and chromosome dynamics during C. elegans female meiosis. BUB-1 is the main chromosome-targeting factor for B56 subunits during prometaphase I. BUB-1 recruits PP2A:B56 to the chromosomes via a newly identified LxxIxE motif in a phosphorylation-dependent manner, and this recruitment is important for proper chromosome congression. Our results highlight a novel mechanism for B56 recruitment, essential for recruiting a pool of PP2A involved in chromosome congression during meiosis I.
Highlights
Formation of a diploid embryo requires that sperm and egg contribute exactly one copy of each chromosome
We found that Phosphatase 2A (PP2A) is essential for female meiosis, and its recruitment to meiotic chromosomes and spindle is mediated by the B56 regulatory subunits PPTR-1 and PPTR-2
PP2A is essential for spindle assembly and chromosome segregation during meiosis I
Summary
Formation of a diploid embryo requires that sperm and egg contribute exactly one copy of each chromosome. The cell division in charge of reducing ploidy of the genome is meiosis, which involves two chromosome segregation steps after a single round of DNA replication (Marston and Amon, 2004; Ohkura, 2015). Female meiosis is error prone (Hassold and Hunt, 2001), which can lead to chromosomally abnormal embryos. Understanding the molecular events that guarantee proper chromosome segregation during female meiosis is of paramount importance. Cell division is under tight control of post-translational modifications (PTMs), of which phosphorylation is the most studied. The balance between kinase and phosphatase activities plays a central role, but we still lack a clear picture of how this is achieved during meiosis, especially when compared to mitosis (Gelens et al, 2018; Novak et al, 2010)
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