%0 Journal Article %T The study of the determinants controlling Arpp19 phosphatase-inhibitory activity reveals an Arpp19/PP2A-B55 feedback loop. %A Labbé JC %A Vigneron S %A Méchali F %A Robert P %A Roque S %A Genoud C %A Goguet-Rubio P %A Barthe P %A Labesse G %A Cohen-Gonsaud M %A Castro A %A Lorca T %J Nat Commun %V 12 %N 1 %D 06 2021 11 %M 34117214 %F 17.694 %R 10.1038/s41467-021-23657-0 %X Arpp19 is a potent PP2A-B55 inhibitor that regulates this phosphatase to ensure the stable phosphorylation of mitotic/meiotic substrates. At G2-M, Arpp19 is phosphorylated by the Greatwall kinase on S67. This phosphorylated Arpp19 form displays a high affinity to PP2A-B55 and a slow dephosphorylation rate, acting as a competitor of PP2A-B55 substrates. The molecular determinants conferring slow dephosphorylation kinetics to S67 are unknown. PKA also phosphorylates Arpp19. This phosphorylation performed on S109 is essential to maintain prophase I-arrest in Xenopus oocytes although the underlying signalling mechanism is elusive. Here, we characterize the molecular determinants conferring high affinity and slow dephosphorylation to S67 and controlling PP2A-B55 inhibitory activity of Arpp19. Moreover, we show that phospho-S109 restricts S67 phosphorylation by increasing its catalysis by PP2A-B55. Finally, we discover a double feed-back loop between these two phospho-sites essential to coordinate the temporal pattern of Arpp19-dependent PP2A-B55 inhibition and Cyclin B/Cdk1 activation during cell division.