PXD052731

PXD052731 is an original dataset announced via ProteomeXchange.

Title	FAM122A ensures cell cycle interphase progression and checkpoint control as a SLiM-dependent substrate-competitive inhibitor to the B55a/PP2A phosphatase
Description	The Ser/Thr protein phosphatase 2A (PP2A) is a highly conserved collection of heterotrimeric holoenzymes responsible for the dephosphorylation of many regulated phosphoproteins. Substrate recognition and the integration of regulatory cues are mediated by B regulatory subunits that are complexed to the catalytic subunit (C) by a scaffold protein (A). PP2A/B55 substrate recruitment was thought to be mediated by charge-charge interactions between the surface of B55a and its substrates. Challenging this view, we recently discovered a conserved SLiM [RK]-V-x-x-[VI]-R in a range of proteins, including substrates such as the retinoblastoma-related protein p107 and TAU (Fowle et al. eLife 2021;10:e63181). Here we report the identification of this SLiM in FAM122A, an inhibitor of B55a/PP2A. This conserved SLiM is necessary for FAM122A binding to B55a in vitro and in cells. Computational structure prediction with AlphaFold-Multimer predicts an interaction consistent with the mutational and biochemical data and supports a mechanism whereby FAM122A uses the 'SLiM' in the form of a short a-helix (helix 1) to dock to the B55a top groove, thereby blocking substrate binding to the same site. In this model, FAM122A also spatially constrains substrate access by occluding the catalytic subunit with a second a-helix immediately adjacent to helix 1. Consistently, FAM122A functions as a competitive inhibitor as it prevents the binding of substrates in in vitro competition assays and the dephosphorylation of CDK substrates by B55a/PP2A in cell lysates. The ablation of FAM122A in human cell lines reduces the rate of proliferation, progression through cell cycle transitions, and abrogates G1/S and intra-S phase cell cycle checkpoints. FAM122A-KO in HEK293 cells results in attenuation of CHK1 and CHK2 activation in response to replication stress. Overall, these data strongly suggest that FAM122A is a short helical motif (SHeM)-dependent, substrate-competitive inhibitor of B55a/PP2A that suppresses multiple functions of B55a in the DNA damage response and in timely progression through the cell cycle interphase.
HostingRepository	MassIVE
AnnounceDate	2024-05-30
AnnouncementXML	Submission_2024-05-30_17:59:11.194.xml
DigitalObjectIdentifier
ReviewLevel	Non peer-reviewed dataset
DatasetOrigin	Original dataset
RepositorySupport	Supported dataset by repository
PrimarySubmitter	Mark Adamo
SpeciesList	scientific name: Homo sapiens; common name: human; NCBI TaxID: 9606;
ModificationList	Carbamidomethyl; Oxidation
Instrument	Q Exactive Plus

Revision	Datetime	Status	ChangeLog Entry
0	2024-05-30 17:11:27	ID requested
⏵ 1	2024-05-30 17:59:11	announced

no publication

submitter keyword: PP2A, FAM122A, B55, retinoblastoma, p107, TAU, SLiM, CDK, interphase

Arminja Kettenbach
contact affiliation	The Geisel School of Medicine at Dartmouth
contact email	arminja.n.kettenbach@dartmouth.edu
lab head
Mark Adamo
contact affiliation	Dartmouth College
contact email	mark.e.adamo@dartmouth.edu
dataset submitter

MassIVE dataset URI

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