Structure and expression of a 72-kDa regulatory subunit of protein phosphatase 2A. Evidence for different size forms produced by alternative splicing

Hendrix, Peter; Mayer-Jackel, R E; Cron, Peter; Goris, Jozef; Hofsteenge, Jan; Merlevede, Wilfried; Hemmings, Brian A.

doi:10.1016/s0021-9258(18)82465-6

Cited by 145 publications

(18 citation statements)

References 47 publications

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“…However, PP2Ac and PR65 appear to be tightly associated (reviewed in reference 10) and therefore it is more likely that a third or ~eariable" regulatory subunit confers nuclear translocation. In this respect it is noteworthy that the primary structure of the PR72 regulatory subunit contains a putative nuclear localization signal (23). Another possibility is that PP2A is specifically retained as nuclei reform in telophase: PP2A was found to translocate out of the nucleus as cells enter mitosis and did not colocalize specifically to the condensed chromatin.…”

Section: Pp2a Is Present In the Cytoplasm And The Nuclei Of Lnterphase Fibroblastsmentioning

confidence: 99%

Differential methylation and altered conformation of cytoplasmic and nuclear forms of protein phosphatase 2A during cell cycle progression.

Turowski

Fernandez

Favre

et al. 1995

The Journal of Cell Biology

144

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Abstract. Protein phosphatase 2A (PP2A) appears to be involved in the regulation of many cellular processes. Control mechanisms that lead to the activation (and deactivation) of the various holoenzymes to initiate appropriate dephosphorylation events remain obscure. The core components of all PP2A holoenzymes are the catalytic (PP2Ac) and 63-65-kD regulatory (PR65) subunits. Monospecific and affinitypurified antibodies against both PP2Ac and PR65 show that these proteins are ubiquitously localized in the cytoplasm and the nucleus in nontransformed fibroblasts. As determined by quantitative immunofluorescence the core subunits of PP2A are twofold more concentrated in the nucleus than in the cytoplasm.Detailed analysis of synchronized cells reveals striking changes in the nuclear to cytoplasmic ratio of PP2Ac-specific immunoreactivity albeit the total amounts of neither PP2Ac nor PR65 in each compartment alters significantly during the cell cycle. Our results imply that differential methylation of PP2Ac occurs at the G0/G1 and GdS boundaries. Specifically a demethylated form of PP2Ac is found in the cytoplasm of G~ cells, and in the nucleus of S and G2 cells. In addition nuclear PP2A holoenzymes appear to undergo conformational changes at the G0/Gt and GJS boundaries. During mitosis PP2A is lost from the nuclear compartment, and unlike protein phosphatase 1 shows no specific association with the condensed chromatin. p ROW~IN phosphatase 2A (PP2A) ~, one of the four major phosphoserine/-threonine phosphatases, has been implicated in the modulation of many events including metabolic regulation (reviewed in reference 10), cell cycle progression (8,16,21,31,35,41,57), DNA replication (58), transcription (3, 59), and protein translation (4, 46). Along with this increasing evidence implicating PP2A in the regulation of all stages of membrane-to-nuclear signal transduction, PP2A has been shown to modulate both protein kinase and phosphatase activity (8,20,53). In addition, a possible role for PP2A in cellular transformation became evident when the dimeric holoenzyme of PP2A was identiffed to be one of the targets for the transforming activities of certain papovaviruses (reviewed in reference 45).It is widely thought that protein phosphatase catalytic subunits exercise regulatory flexibility and differential substrate

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Section: Pp2a Is Present In the Cytoplasm And The Nuclei Of Lnterphase Fibroblastsmentioning

confidence: 99%

Differential methylation and altered conformation of cytoplasmic and nuclear forms of protein phosphatase 2A during cell cycle progression.

Turowski

Fernandez

Favre

et al. 1995

The Journal of Cell Biology

144

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“…In addition, PP2A 1 and PP2A 0 contain several distinct B (B, B′, and B′′) subunits with apparent M r values of approximately 54 000, 55 000, 56 000, 72 000, and 130 000 [e.g. Hemmings et al (1990), Hendrix et al (1993), Zolnierowicz et al (1994), McCright and Virshup (1995), and Csortos et al (1996)]. By contrast, only two forms of each of the A and C subunits exhibiting 86% (Hemmings et al, 1990;Mayer et al, 1991) and 97% identity (Da Cruz e Silva Stone et al, 1987;Arino et al, 1988;Sneddon et al, 1990) in their predicted amino acid sequences, respectively, have been identified by molecular cloning methods.…”

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confidence: 99%

Molecular Identification of I₁^PP2A, a Novel Potent Heat-Stable Inhibitor Protein of Protein Phosphatase 2A

1996

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The amino acid sequences of two tryptic peptides derived from purified preparations of I 1 PP2A indicated that this potent heat-stable protein inhibitor of protein phosphatase 2A (PP2A) may be equivalent to putative histocompatibility leukocyte antigens class II-associated protein I (PHAP-I). Experiments using purified preparations of recombinant human PHAP-I confirmed that this protein inhibited PP2A. Half-maximal inhibition of the phosphatase occurred at about 4 nM PHAP-I, similar to the half-maximal inhibition obtained with purified preparations of bovine kidney I 1 PP2A . In addition, PHAP-I did not affect the activities of protein phosphatase 1, 2B, and 2C in a manner analogous to that of I 1 PP2A . Together, the results establish the identity of I 1 PP2A on a firm basis.

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“…Multimeric forms of PP2A (see Fig. 1C) were purified from rabbit skeletal muscle, and free catalytic subunit was purified from bovine heart (2,6,16). Concentrations of the different forms of PP2A were determined by densitometric quantitation of the 36-kDa catalytic subunit on both immunoblots and silver-stained sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) gels.…”

Section: Materuils and Methodsmentioning

confidence: 99%

“…At least three distinct B subunits of 72, 55, and 54 kDa have been purified to date from skeletal and cardiac muscle and erythrocytes. cDNAs for the 55-and 72-kDa forms (and a 130-kDa splice variant) have been cloned (16,22). Interestingly, small t antigen of SV40 and small and middle T antigens of polyomavirus can also bind to the A-C complex in place of endogenous B subunits, leading to alterations in phosphatase activity (references 4 and 38 and references therein).…”

mentioning

confidence: 99%

Different Oligomeric Forms of Protein Phosphatase 2A Activate and Inhibit Simian Virus 40 DNA Replication

Cegielska

Shaffer

Derua

et al. 1994

Molecular and Cellular Biology

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The ability of simian virus 40 (SV40) large T antigen to catalyze the initiation of viral DNA replication is regulated by its phosphorylation state. Previous studies have identified the free catalytic subunit of protein phosphatase 2A (PP2Ac) as the cellular phosphatase which can remove inhibitory phosphoryl groups from serines 120 and 123. The catalytic C subunit exists in the cell complexed with a 65-kDa A subunit and one of several B subunits. To determine if any of the holoenzymes could activate T antigen, we tested the ability of the heterodimeric AC and two heterotrimeric ABC forms to stimulate T-antigen function in unwinding the origin of SV40 DNA replication. Only free catalytic subunit C and the heterotrimeric form with a 72-kDa B subunit (PP2A-T72) could stimulate T-antigen-dependent origin unwinding. Both the dimeric form (PP2A-D) and the heterotrimer with a 55-kDa B subunit (PP2A-T55) actively inhibited T-antigen function. We found that PP2A-T72 activated T antigen by dephosphorylating serines 120 and 123, while PP2A-D and PP2A-T55 inactivated T antigen by dephosphorylating the p34cdc2 target site, threonine 124. Thus, alterations in the subunit composition of PP2A holoenzymes have significant functional consequences for the initiation of in vitro SV40 DNA replication. The regulatory B subunits of PP2A may play a role in regulating SV40 DNA replication in infected cells as well.

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Structure and expression of a 72-kDa regulatory subunit of protein phosphatase 2A. Evidence for different size forms produced by alternative splicing

Cited by 145 publications

References 47 publications

Differential methylation and altered conformation of cytoplasmic and nuclear forms of protein phosphatase 2A during cell cycle progression.

Differential methylation and altered conformation of cytoplasmic and nuclear forms of protein phosphatase 2A during cell cycle progression.

Molecular Identification of I₁^PP2A, a Novel Potent Heat-Stable Inhibitor Protein of Protein Phosphatase 2A

Different Oligomeric Forms of Protein Phosphatase 2A Activate and Inhibit Simian Virus 40 DNA Replication

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Structure and expression of a 72-kDa regulatory subunit of protein phosphatase 2A. Evidence for different size forms produced by alternative splicing

Cited by 145 publications

References 47 publications

Differential methylation and altered conformation of cytoplasmic and nuclear forms of protein phosphatase 2A during cell cycle progression.

Differential methylation and altered conformation of cytoplasmic and nuclear forms of protein phosphatase 2A during cell cycle progression.

Molecular Identification of I1PP2A, a Novel Potent Heat-Stable Inhibitor Protein of Protein Phosphatase 2A

Different Oligomeric Forms of Protein Phosphatase 2A Activate and Inhibit Simian Virus 40 DNA Replication

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Molecular Identification of I₁^PP2A, a Novel Potent Heat-Stable Inhibitor Protein of Protein Phosphatase 2A