title: The PP2A inhibitor I2PP2A is essential for sister chromatid segregation in oocyte meiosis II.
abstract: Haploid gametes are generated through two consecutive meiotic divisions, with the segregation of chromosome pairs in meiosis I and sister chromatids in meiosis II. Separase-mediated stepwise removal of cohesion, first from chromosome arms and later from the centromere region, is a prerequisite for maintaining sister chromatids together until their separation in meiosis II [1]. In all model organisms, centromeric cohesin is protected from separase-dependent removal in meiosis I through the activity of PP2A-B56 phosphatase, which is recruited to centromeres by shugoshin/MEI-S332 (Sgo) [2-5]. How this protection of centromeric cohesin is removed in meiosis II is not entirely clear; we find that all the PP2A subunits remain colocalized with the cohesin subunit Rec8 at the centromere of metaphase II chromosomes. Here, we show that sister chromatid separation in oocytes depends on a PP2A inhibitor, namely I2PP2A. I2PP2A colocalizes with the PP2A enzyme at centromeres at metaphase II, independently of bipolar attachment. When I2PP2A is depleted, sister chromatids fail to segregate during meiosis II. Our findings demonstrate that in oocytes I2PP2A is essential for faithful sister chromatid segregation by mediating deprotection of centromeric cohesin in meiosis II.
authors: UPMC University of Paris 6, 75005 Paris, France. jean-philippe.chambon@snv.jussieu.fr
authors: Jean-Philippe
authors: JP
authors: Chambon
authors: Sandra A
authors: SA
authors: Touati
authors: Stéphane
authors: S
authors: Berneau
authors: Damien
authors: D
authors: Cladière
authors: Céline
authors: C
authors: Hebras
authors: Rachel
authors: R
authors: Groeme
authors: Alex
authors: A
authors: McDougall
authors: Katja
authors: K
authors: Wassmann
mesh_terms: D000818:Animals; D002938:Ciona intestinalis / Q000235:genetics / Q000502:physiology*; D008297:Male; D008540:Meiosis; D051379:Mice; D009865:Oocytes / Q000502:physiology; D016133:Polymerase Chain Reaction; D054648:Protein Phosphatase 2 / Q000378:metabolism*; D012854:Sister Chromatid Exchange; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: D014157:Transcription Factors; D054648:Protein Phosphatase 2