The M-phase regulatory phosphatase PP2A-B55d opposes protein kinase A on Arpp19 to initiate meiotic division

Tom Lemonnier, Enrico Maria Daldello, Robert Poulhe, Tran Le, Marika Miot, Catherine Jessus, Aude Dupré

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Nov 11, 2019
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Received Date: 22nd October 19

Oocytes are held in meiotic prophase for prolonged periods until hormonal signals trigger meiotic divisions. Key players of M-phase entry are the opposing Cdk1 kinase and PP2A-B55d phosphatase. In Xenopus, the protein Arpp19, phosphorylated at serine 67 by Greatwall, plays an essential role in inhibiting PP2A-B55d, promoting Cdk1 activation. Furthermore Arpp19 has an earlier role in maintaining the prophase arrest through a second serine (S109) phosphorylated by PKA. Prophase release, induced by progesterone, relies on Arpp19 dephosphorylation at S109, owing to an unknown phosphatase. Here we identified this phosphatase as PP2A-B55d. In prophase, PKA and PP2A-B55d are simultaneously active, suggesting the presence of other important targets for both enzymes. The drop in PKA activity induced by progesterone enables PP2A-B55d to dephosphorylate S109, unlocking the prophase block. Hence, PP2A-B55d acts critically on Arpp19 on two distinct sites, opposing PKA and Greatwall to orchestrate the prophase release and M-phase entry.

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This is an abstract of a preprint hosted on an independent third party site. It has not been peer reviewed but is currently under consideration at Nature Communications.

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