Toxicity of human adenovirus E4orf4 protein in Saccharomyces cerevisiae results from interactions with the Cdc55 regulatory B subunit of PP2A

Roopchand, Diana E.; Lee, Joseph M.; Shahinian, Serge; Paquette, Denis; Bussey, Howard; Branton, Philip E.

doi:10.1038/sj.onc.1204693

Cited by 59 publications

(108 citation statements)

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“…When the inducers of CAT expression were cotransfected with pBELMCAT, higher levels of CAT were observed with the higher concentration of PTB and SRp30c, respectively. In contrast, E4orf4 decreased CAT expression at higher concentrations; a result that might be correlated to other studies where adenovirus E4orf4 had shown to induce apoptosis (Kleinberger, 2000;Kornitzer et al, 2001;Roopchand et al, 2001). Taken The reporters were also constructed using the luciferase gene and proved equally sensitive in transient transfections.…”

Section: Discussionmentioning

confidence: 77%

Development and validation of a novel reporter assay for human papillomavirus type 16 late gene expression

Orru¹,

Cunniffe²,

Ryan³

et al. 2012

Journal of Virological Methods

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Section: Discussionmentioning

confidence: 77%

Development and validation of a novel reporter assay for human papillomavirus type 16 late gene expression

Orru¹,

Cunniffe²,

Ryan³

et al. 2012

Journal of Virological Methods

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“…Even though these viruses are not otherwise related, they all seem to have adapted a similar strategy to affect cellular processes by direct interaction with PP2A. Similar to the Vpr effects, both adenoviral E4orf4 [63][64][65] and HTLV Tax protein induce cell cycle G2 arrest [59]. These two viral proteins both bind to PP2A and affect its enzymatic activity [63,66].…”

Section: Potential Role Of Pp2a In Cell Cycle G2/m Regulation During mentioning

confidence: 99%

Viral infections and cell cycle G2/M regulation

Zhao

Elder

2005

Cell Res

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Progression of cells from G2 phase of the cell cycle to mitosis is a tightly regulated cellular process that requires activation of the Cdc2 kinase, which determines onset of mitosis in all eukaryotic cells. In both human and fission yeast (Schizosaccharomyces pombe) cells, the activity of Cdc2 is regulated in part by the phosphorylation status of tyrosine 15 (Tyr15) on Cdc2, which is phosphorylated by Wee1 kinase during late G2 and is rapidly dephosphorylated by the Cdc25 tyrosine phosphatase to trigger entry into mitosis. These Cdc2 regulators are the downstream targets of two wellcharacterized G2/M checkpoint pathways which prevent cells from entering mitosis when cellular DNA is damaged or when DNA replication is inhibited. Increasing evidence suggests that Cdc2 is also commonly targeted by viral proteins, which modulate host cell cycle machinery to benefit viral survival or replication. In this review, we describe the effect of viral protein R (Vpr) encoded by human immunodeficiency virus type 1 (HIV-1) on cell cycle G2/M regulation. Based on our current knowledge about this viral effect, we hypothesize that Vpr induces cell cycle G2 arrest through a mechanism that is to some extent different from the classic G2/M checkpoints. One the unique features distinguishing Vpr-induced G2 arrest from the classic checkpoints is the role of phosphatase 2A (PP2A) in Vpr-induced G2 arrest. Interestingly, PP2A is targeted by a number of other viral proteins including SV40 small T antigen, polyomavirus T antigen, HTLV Tax and adenovirus E4orf4. Thus an in-depth understanding of the molecular mechanisms underlying Vpr-induced G2 arrest will provide additional insights into the basic biology of cell cycle G2/M regulation and into the biological significance of this effect during host-pathogen interactions.

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“…Toxicity in Yeast-The protocol used to select for CDC55 mutants that have lost the ability to transduce the E4orf4 toxic effect was based on the findings that E4orf4 inhibits growth of WT yeast but not of cdc55⌬ cells, and that ectopic expression of a WT CDC55 gene in the cdc55⌬ background restores E4orf4 toxicity (27,36). It also relies on the finding that E4orf4-induced cell death requires an interaction between E4orf4 and an active PP2A, containing both catalytic and regulatory subunits (22,23).…”

Section: Selection For Cdc55 Mutants That Cannot Mediate E4orf4mentioning

confidence: 99%

The Scaffolding A/Tpd3 Subunit and High Phosphatase Activity Are Dispensable for Cdc55 Function in the Saccharomyces cerevisiae Spindle Checkpoint and in Cytokinesis

Koren¹,

Rainis²,

Kleinberger

2004

Journal of Biological Chemistry

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Protein serine/threonine phosphatase 2A (PP2A) is a multifunctional enzyme whose trimeric form consists of a scaffolding A subunit, a catalytic C subunit, and one of several regulatory B subunits (B, B , and B؆). The adenovirus E4orf4 protein associates with PP2A by directly binding the B or B subunits. An interaction with an active PP2A containing the B subunit, or its homologue in yeast, Cdc55, is required for E4orf4-induced apoptosis in mammalian cells and for induction of growth arrest in Saccharomyces cerevisiae. In this work, Cdc55 was randomly mutagenized by low-fidelity PCR amplification, and Cdc55 mutants that lost the ability to transduce the E4orf4 toxic signal in yeast were selected. The mutations obtained by this protocol inhibited the association of Cdc55 with E4orf4, or with the PP2A-AC subunits, or both. Functional analysis revealed that a mutant that does not bind Tpd3, the yeast A subunit, as well as wild type Cdc55 in a tpd3⌬ background, can form a heterodimer with the catalytic subunit. This association requires C subunit carboxyl methylation. The residual phosphatase activity associated with Cdc55 in the absence of Tpd3 is sufficient to maintain a partially active spindle checkpoint and to prevent cytokinesis defects.PP2A 1 is one of the major protein serine/threonine phosphatases in the cell, which plays a role in several cellular processes, including metabolism, transcription, RNA splicing, translation, cell cycle progression, morphogenesis, signal transduction, development, and transformation (1, 2).Several reports indicate that the predominant form of PP2A in cells is a heterotrimer consisting of three subunits. Two of them, the 36-kDa catalytic C subunit and the 63-kDa scaffolding A subunit (PR65), form the core enzyme, and the regulatory B subunit binds the core enzyme to form the holoenzyme. The A and C subunits both exist as two isoforms (␣ and ␤), which are closely related, whereas the B subunit is variable, and its multiple isoforms belong to at least three unrelated gene families, B/B55/PR55 (␣-␦ isoforms), BЈ/B56/PR61 (␣-⑀ isoforms), and BЉ/PR72/PR130/PR59/PR48 (3). The core PP2A enzyme has also been shown to bind other cellular proteins, including striatin and SG2NA (4). Viral proteins, such as the SV40 small t antigen and the polyomavirus small and middle T antigens, can replace the cellular B subunits (5). The various cellular PP2A B subunits target the PP2A holoenzyme to different substrates and dictate its subcellular localization (reviewed in Ref.3).In Saccharomyces cerevisiae, two closely related genes, PPH21 and PPH22, redundantly encode the major PP2A catalytic subunit (6). TPD3 encodes the only A subunit, and two distinct B subunits, encoded by CDC55 and RTS1, are highly homologous to mammalian B and BЈ, respectively (7-9). Mutations of CDC55 are viable, but yield defects in cytokinesis and in the spindle checkpoint and result in abnormal cell morphology. Methylation of the C-terminal leucine residue of the PP2A catalytic subunit by a specific methyltransferase increase...

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Toxicity of human adenovirus E4orf4 protein in Saccharomyces cerevisiae results from interactions with the Cdc55 regulatory B subunit of PP2A

Cited by 59 publications

References 58 publications

Development and validation of a novel reporter assay for human papillomavirus type 16 late gene expression

Development and validation of a novel reporter assay for human papillomavirus type 16 late gene expression

Viral infections and cell cycle G2/M regulation

The Scaffolding A/Tpd3 Subunit and High Phosphatase Activity Are Dispensable for Cdc55 Function in the Saccharomyces cerevisiae Spindle Checkpoint and in Cytokinesis

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