Molecular model of the A subunit of protein phosphatase 2A: interaction with other subunits and tumor antigens

Ruediger, Ralf; Hentz, M; Fait, J; Mumby, Marc C.; Walter, Gernot

doi:10.1128/jvi.68.1.123-129.1994

Cited by 138 publications

(81 citation statements)

References 21 publications

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“…In order to establish the PP2A subunit responsible for interaction with eRF1, we performed direct interaction analysis using the yeast two-hybrid system (Fields and Song, 1989). One could expect PR65 as the likely candidate for this interaction, since it is known to bind to both the catalytic and variable regulatory subunits, thus performing a scaffold-like function for assembly of PP2A holoenzymes (Ruediger et al, 1994). Surprisingly, eRFI turned out to interact directly and specifically with the catalytic subunit of PP2A and apparently did not bind either PR65 or PR55 in the yeast two-hybrid system.…”

Section: Discussionmentioning

confidence: 99%

The catalytic subunit of protein phosphatase 2A associates with the translation termination factor eRF1.

et al. 1996

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By a number of criteria, we have demonstrated that the translation termination factor eRF1 (eukaryotic release factor 1) associates with protein phosphatase 2A (PP2A). Trimeric PP2A1 was purified from rabbit skeletal muscle using an affinity purification step. In addition to the 36 kDa catalytic subunit (PP2Ac) and established regulatory subunits of 65 kDa (PR65) and 55 kDa (PR55), purified preparations contained two proteins with apparent Mrs of 54 and 55 kDa. Protein microsequencing revealed that the 55 kDa component is a novel protein, whereas the 54 kDa protein was identified as eRF1, a protein that functions in translational termination as a polypeptide chain release factor. Using the yeast two‐hybrid system, human eRF1 was shown to interact specifically with PP2Ac, but not with the PR65 or PR55 subunits. By deletion analysis, the binding domains were found to be located within the 50 N‐terminal amino acids of PP2Ac, and between amino acid residues 338 and 381 in the C‐terminal part of human eRF1. This association also occurs in vivo, since PP2A can be co‐immunoprecipitated with eRF1 from mammalian cells. We observed a significant increase in the amount of PP2A associated with the polysomes when eRF1 was transiently expressed in COS1 cells, and eRF1 immunoprecipitated from those fractions contained associated PP2A. Since we did not observe any dramatic effects of PP2A on the polypeptide chain release activity of eRF1 (or vice versa), we postulate that eRF1 also functions to recruit PP2A into polysomes, thus bringing the phosphatase into contact with putative targets among the components of the translational apparatus.

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Section: Discussionmentioning

confidence: 99%

The catalytic subunit of protein phosphatase 2A associates with the translation termination factor eRF1.

et al. 1996

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“…The region in PR65 surrounding Lys416 is important for binding to PP2Ac. The primary structure of PR65 has 15 imperfect repeats of 39 amino acids (Hemmings et al, 1990), and the current structural model (Ruediger et al, 1994) predicts that each of the 15 repeats forms a similar helix-loop-helix-loop unit and that these are arranged in a linear fashion (Fig. 6A).…”

Section: Modulation Of Pp2ac Activity By Recombinant Pr65 Is Dependenmentioning

confidence: 97%

“…PR6.5 consists of 1.5 imperfect repeats (Hemmings et al, 1990) and has a rod-like shape with an axial ratio of 10..5:1 (Chen et al, 1989). Based on these data, a structural model was proposed in which each repeat forms a module of two anti-parallel a helices, and 1.5 of these modules are aligned next to each other (Ruediger et al, 1992(Ruediger et al, , 1994. It was predicted that the loops connecting the anti-parallel a helices within a module serve as binding sites for PP2Ac and the variable regulatory subunits.…”

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confidence: 99%

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Modulation of the Enzymatic Properties of Protein Phosphatase 2A Catalytic Subunit by the Recombinant 65‐kDa Regulatory Subunit PR65α

Turowski¹,

Favre²,

Campbell³

et al. 1997

European Journal of Biochemistry

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All protein phosphatase 2A (PP2A) holoenzymes contain a 36-kDa catalytic subunit (PP2Ac) and a regulatory subunit of 6.5 kDa (PR6.5). We have studied the interaction between PP2Ac and PR65 in an in vitro system, using PP2Ac isolated from rabbit skeletal muscle and recombinant PR6Sa expressed in bacteria or insect cells. Bacterially expressed PR6Sa exhibited identical biochemical properties to the protein expressed and isolated from the baculoviral expression system. The association of recombinant PR6.5 with PP2Ac was very tight (&fP = 85 pM) and led to a suppression of PP2A activity, which was maximal (70-80 %) when phosphoproteins were used as substrates. When less-structured or smaller substrates (such as phosphopeptides) were used, this inhibition was only 30 %. PR6.5 stimulated PP2Ac activity when the assays were performed in the presence of polycations. This indicates that the PR6.5 not only serves the previously predicted structural role as a molecular scaffold, but also allosterically modulates the enzymatic properties of PP2Ac. Furthermore, we identified a site of interaction between PP2Ac and PR6Sa by disruption of a stretch of basic amino acids by introduction of a glutamate at position 416. This produced an almost 100-fold reduced affinity for PP2Ac and indicated that this basic motif is an important determinant for the interaction of PR6.5 and PP2Ac.

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“…PP2A inhibitors such as okadaic acid are known tumor inducers and the small t antigen of SV40 transforms cells in culture by replacing B subunits suggesting that certain PP2A B subunits might have tumor suppressor activity (Ruediger et al, 1994;Janssens et al, 2005). In addition, several prior in vitro studies have specifically identified B56g as a potential tumor suppressor (Chen et al, 2004;Li et al, 2007;Shouse et al, 2011).…”

Section: Developmental Dynamicsmentioning

confidence: 99%

The protein phosphatase 2A B56γ regulatory subunit is required for heart development

Varadkar

Despres

Kraman

et al. 2014

Developmental Dynamics

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Background: Protein Phosphatase 2A (PP2A) function is controlled by regulatory subunits that modulate the activity of the catalytic subunit and direct the PP2A complex to specific intracellular locations. To study PP2A's role in signal transduction pathways that control growth and differentiation in vivo, a transgenic mouse lacking the B56g regulatory subunit of PP2A was made. Results: Lack of PP2A activity specific to the PP2A-B56g holoenzyme, resulted in the formation of an incomplete ventricular septum and a decrease in the number of ventricular cardiomyocytes. During cardiac development, B56g is expressed in the nucleus of a-actinin-positive cardiomyocytes that contain Z-bands. The pattern of B56g expression correlated with the cardiomyocyte apoptosis we observed in B56g-deficient mice during mid to late gestation. In addition to the cardiac phenotypes, mice lacking B56g have a decrease in locomotive coordination and gripping strength, indicating that B56g has a role in controlling PP2A activity required for efficient neuromuscular function. Conclusions: PP2A-B56g activity is required for efficient cardiomyocyte maturation and survival. The PP2A B56g regulatory subunit controls PP2A substrate specificity in vivo in a manner that cannot be fully compensated for by other B56 subunits. Developmental Dynamics 243:778-790,

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Molecular model of the A subunit of protein phosphatase 2A: interaction with other subunits and tumor antigens

Cited by 138 publications

References 21 publications

The catalytic subunit of protein phosphatase 2A associates with the translation termination factor eRF1.

The catalytic subunit of protein phosphatase 2A associates with the translation termination factor eRF1.

Modulation of the Enzymatic Properties of Protein Phosphatase 2A Catalytic Subunit by the Recombinant 65‐kDa Regulatory Subunit PR65α

The protein phosphatase 2A B56γ regulatory subunit is required for heart development

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