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A highly conserved pocket on PP2A-B56 is required for hSgo1 binding and cohesion protection during mitosis

ABSTRACT: The shugoshin proteins are universal protectors of centromeric cohesin during mitosis and meiosis. The binding of human hSgo1 to the PP2A-B56 phosphatase through a coiled coil (CC) region mediates cohesion protection during mitosis. Here we undertook a structure function analysis of the PP2A-B56-hSgo1 complex, revealing unanticipated aspects of complex formation and function. We establish that a highly conserved pocket on the B56 regulatory subunit is required for hSgo1 binding and cohesion protection during mitosis in human somatic cells. Consistent with this, we show that hSgo1 blocks the binding of PP2A-B56 substrates containing a canonical B56 binding motif. We find that PP2A-B56 bound to hSgo1 dephosphorylates Cdk1 sites on hSgo1 itself to modulate cohesin interactions. Collectively our work provides important insight into cohesion protection during mitosis.

INSTRUMENT(S): Orbitrap Fusion Lumos, Orbitrap Fusion, Q Exactive Plus

ORGANISM(S): Homo Sapiens (ncbitaxon:9606)

SUBMITTER: Arminja Kettenbach

PROVIDER: MSV000087003 | MassIVE | Thu Mar 04 16:38:00 GMT 2021

SECONDARY ACCESSION(S): PXD024532

REPOSITORIES: MassIVE

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Structural mechanism for inhibition of PP2A-B56 and oncogenicity by CIP2A

Project description:Abstract The protein phosphatase 2A (PP2A) heterotrimer PP2A-B56 is a human tumor suppressor. However, the molecular mechanisms inhibiting PP2A-B56in cancer are poorly understood. Here, we report molecular level details and structural mechanism of PP2A-B56inhibition by an oncoprotein CIP2A. Upon direct binding to PP2A-B56 trimer, CIP2A replaces PP2A-A subunit and thereby hijacks both the B56 and the catalytic PP2Ac subunit to form a CIP2A-B56-PP2Ac pseudotrimer. Further, CIP2A competes with B56 substrate binding by blocking the LxxIxE-motif substrate binding pocket on B56. Relevant to oncogenic activity of CIP2A across human cancers, the N-terminal head domain-mediated interaction with B56 stabilizes CIP2A protein. Functionally, CRISPR/Cas9-mediated single amino acid mutagenesis of the head domain blunted MYC expression and MEK phosphorylation, and abrogated triple-negative breast cancer in vivo tumor growth. Collectively, we discover a unique multi-step “hijack and mute” mechanism of protein complex regulation inhibiting tumor suppressor PP2A-B56. Further, the results unfold single structural determinant for CIP2A´s oncogenic activity, potentially facilitating therapeutic modulation of CIP2A in cancer and other diseases.

2023-03-11 | PXD030297 | Pride

SCF-Fbxo42 promotes synaptonemal complex assembly by downregulating PP2A-B56

Project description:Meiosis creates genetic diversity by recombination and segregation of chromosomes. The synaptonemal complex assembles during meiotic prophase I and assists faithful exchanges between homologous chromosomes, but how its assembly/disassembly is regulated remains to be understood. Here we report how two major post-translational modifications, phosphorylation and ubiquitination, co-operate to promote synaptonemal complex assembly. We found that the ubiquitin ligase complex SCF is important for assembly and maintenance of the synaptonemal complex in Drosophila female meiosis. This function of SCF is mediated by two substrate-recognising F-box proteins, Slmb/βTrcp and Fbxo42. SCF-Fbxo42 downregulates the phosphatase subunit PP2A-B56, which is important for synaptonemal complex assembly and maintenance.

2020-12-07 | PXD022755 | Pride

A dynamic charge:charge interaction modulates PP2A:B56 interactions

Project description:The recruitment of specific substrates by ser/thr protein phosphatase 2A (PP2A) regulatory B-subunits is poorly understood, limiting our understanding of PP2A-regulated signaling. Recently, the first PP2A:B56 consensus binding motif, LxxIxE, which confers substrate specificity to PP2A:B56 holoenzymes, was identified. However, most validated LxxIxE motifs interact with PP2A:B56 with low micromolar affinities, suggesting that additional recognition motifs exist that function cooperatively to enhance PP2A:B56 binding. Here, we report the requirement of a positively charged motif in a subset of PP2A:B56 interactors that facilitates B56 binding via dynamic charge:charge interactions. Using molecular and cellular approaches, we show that a highly conserved, negatively charged groove on B56 mediates this dynamic interaction. We also show that this motif is required for efficient binding and dephosphorylation of KIF4A in cells, confirming the functional relevance of this motif for PP2A:B56 dephosphorylation. Collectively our results provide an important framework for understanding PP2A regulation of cellular signaling.

2019-05-16 | MSV000083785 | MassIVE

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2019-08-28 | MSV000084245 | MassIVE

Protein phosphatase 2A protects centromeric sister chromatid cohesion during meiosis I

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2006-05-10 | GSE4791 | GEO

A complex of BRCA2 and PP2A-B56 is required for homologous recombination-mediated DNA repair

Project description:Mutations in the tumour suppressor BRCA2 are associated with predisposition to breast and ovarian cancers. BRCA2 has a central role in genome integrity by facilitating the repair of toxic DNA double-strand breaks (DSBs) by homologous recombination. BRCA2 acts by promoting RAD51 nucleofilament formation on resected single-stranded DNA, but how BRCA2 activity is regulated during HR is not fully understood. Here, we delineate a pathway where ATM and ATR kinases phosphorylate a highly conserved region in BRCA2 in response to DNA DSBs. These phosphorylations stimulate the binding of the protein phosphatase PP2A-B56 to BRCA2 through a conserved binding motif. We show that the phosphorylation-dependent formation of the BRCA2-PP2A-B56 complex is required for efficient RAD51 loading to sites of DNA damage and HR-mediated DNA repair. Moreover, we find that several cancer-associated mutations in BRCA2 deregulate the BRCA2-PP2A-B56 interaction and sensitize cells to PARP inhibition. Collectively, our work uncovers PP2A-B56 as a positive regulator of BRCA2 function in HR with clinical implications for BRCA2 and PP2A-B56 mutated cancers.

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Mapping of cohesion factor association sites in S. cerevisiae - Meiosis I chromosome segregation is established through regulation of microtubule-kinetochore interactions.

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2012-10-05 | E-GEOD-41339 | biostudies-arrayexpress

Reductional meiosis I chromosome segregation is established by coordination of key meiotic kinases

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2019-11-13 | PXD012627 | Pride

Mapping of cohesion factor association sites in S. cerevisiae - Meiosis I chromosome segregation is established through regulation of microtubule-kinetochore interactions.

2012-10-05 | GSE41339 | GEO

TBP ChIP-chip on Jurkat cells

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2010-04-03 | E-GEOD-12256 | biostudies-arrayexpress

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