Identification of PP2A-B55 targets in Drosophila uncovers regulation of Emerin during nuclear envelope reassembly

ABSTRACT: Entry into mitosis is triggered by mitotic kinases that phosphorylate multiple proteins to induce profound cellular changes including nuclear envelope breakdown, chromosome condensation and spindle assembly. Conversely, mitotic exit requires protein dephosphorylation as cells return to their interphase organization. Protein Phosphatase 2A in complex with its B55/Tws regulatory subunit (PP2A-B55) is known to play a crucial role in this transition. However, the precise events and substrates that it regulates are incompletely understood. We used proteomic approaches in Drosophila to identify proteins that interact with PP2A-B55 and are dephosphorylated in a PP2A-B55 dependent manner. Among several candidates, we identified Otefin (also known as Emerin) as a target of PP2A-B55 in the process of nuclear envelope reformation after mitosis. Emerin is a protein of the inner nuclear membrane that interacts with the DNA-binding protein Barrier-to-Autointegration Factor (BAF) via a LEM domain. Our results indicate that phosphorylation of Emerin at Ser50 and Ser54 near its LEM domain negatively regulates its association with BAF, Lamin and additional Emerin. Using live imaging, we show that dephosphorylation of Emerin at the identified sites determines the timing of nuclear envelope reformation. Genetic rescue experiments indicate that this regulation is required in vivo during embryonic development. Phosphoregulation of the Emerin-BAF complex formation by PP2A-B55 appears as a key event of mitotic exit that is likely to be conserved across species.

INSTRUMENT(S): LTQ Orbitrap

ORGANISM(S): Drosophila Melanogaster (fruit Fly)

TISSUE(S): Cell Culture

SUBMITTER: Eric Bonneil  

LAB HEAD: Vincent Archambault

PROVIDER: PXD041030 | Pride | 2023-08-10

REPOSITORIES: Pride