<i>NTPDASE4</i>
            Gene Products Cooperate with the Adenovirus E4orf4 Protein through PP2A-Dependent and -Independent Mechanisms and Contribute to Induction of Cell Death

Avital-Shacham, Meirav; Sharf, Rakefet; Kleinberger, Tamar

doi:10.1128/jvi.00381-14

Cited by 8 publications

(11 citation statements)

References 41 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Cell death assay: the DAPI assay. DAPI assays, which determine nuclear aberrations, have been described previously (68,69). Briefly, cells were transfected with plasmids expressing E4orf4.…”

Section: Fig 11mentioning

confidence: 99%

Biphasic Functional Interaction between the Adenovirus E4orf4 Protein and DNA-PK

Nebenzahl-Sharon

Shalata

Sharf

et al. 2019

J Virol

Self Cite

View full text Add to dashboard Cite

The adenovirus (Ad) E4orf4 protein contributes to virus-induced inhibition of the DNA damage response (DDR) by reducing ATM and ATR signaling. Consequently, E4orf4 inhibits DNA repair and sensitizes transformed cells to killing by DNA-damaging drugs. Inhibition of ATM and ATR signaling contributes to the efficiency of virus replication and may provide one explanation for the cancer selectivity of cell death induced by the expression of E4orf4 alone. In this report, we investigate a direct interaction of E4orf4 with the DDR. We show that E4orf4 physically associates with the DNA-dependent protein kinase (DNA-PK), and we demonstrate a biphasic functional interaction between these proteins, wherein DNA-PK is required for ATM and ATR inhibition by E4orf4 earlier during infection but is inhibited by E4orf4 as infection progresses. This biphasic process is accompanied by initial augmentation and a later inhibition of DNA-PK autophosphorylation as well as by colocalization of DNA-PK with early Ad replication centers and distancing of DNA-PK from late replication centers. Moreover, inhibition of DNA-PK improves Ad replication more effectively when a DNA-PK inhibitor is added later rather than earlier during infection. When expressed alone, E4orf4 is recruited to DNA damage sites in a DNA-PK-dependent manner. DNA-PK inhibition reduces the ability of E4orf4 to induce cancer cell death, likely because E4orf4 is prevented from arriving at the damage sites and from inhibiting the DDR. Our results support an important role for the E4orf4 -DNA-PK interaction in Ad replication and in facilitation of E4orf4-induced cancer-selective cell death.IMPORTANCE Several DNA viruses evolved mechanisms to inhibit the cellular DNA damage response (DDR), which acts as an antiviral defense system. We present a novel mechanism by which the adenovirus (Ad) E4orf4 protein inhibits the DDR. E4orf4 interacts with the DNA damage sensor DNA-PK in a biphasic manner. Early during infection, E4orf4 requires DNA-PK activity to inhibit various branches of the DDR, whereas it later inhibits DNA-PK itself. Furthermore, although both E4orf4 and DNA-PK are recruited to virus replication centers (RCs), DNA-PK is later distanced from late-phase RCs. Delayed DNA-PK inhibition greatly contributes to Ad replication efficiency. When E4orf4 is expressed alone, it is recruited to DNA damage sites. Inhibition of DNA-PK prevents both recruitment and the previously reported ability of E4orf4 to kill cancer cells. Our results support an important role for the E4orf4 -DNA-PK interaction in Ad replication and in facilitation of E4orf4-induced cancer-selective cell death.

show abstract

Section: Fig 11mentioning

confidence: 99%

Biphasic Functional Interaction between the Adenovirus E4orf4 Protein and DNA-PK

Nebenzahl-Sharon

Shalata

Sharf

et al. 2019

J Virol

Self Cite

View full text Add to dashboard Cite

show abstract

“…The knockdown of NTPDASE4 suppressed E4orf4 induced cell death while overexpression enhanced E4orf4-induced cell killing. Study findings suggest that the E4orf4-NTPDase4 pathway, partly in association with PP2A, may provide an alternative mechanism to contribute to the cytoplasmic death function of E4orf4 [166].…”

Section: Subcellular Localization and Mechanism Of Action: Cytoplasmimentioning

confidence: 99%

“…Cabon et al [165] added that arrested cells died due to accumulation of both diploid and tetraploid cells, which are unable to initiate DNA synthesis. Recently, Avital-Shacham et al [166] reported that the NTPDASE4 gene product Gogi UDPase, a mammalian orthologue of yeast Ynd1, interacts with E4orf4. The knockdown of NTPDASE4 suppressed E4orf4 induced cell death while overexpression enhanced E4orf4-induced cell killing.…”

Section: Subcellular Localization and Mechanism Of Action: Cytoplasmimentioning

confidence: 99%

Viral genes as oncolytic agents for cancer therapy

Gupta

Gandham

Sahoo

et al. 2014

Cell. Mol. Life Sci.

View full text Add to dashboard Cite

Many viruses have the ability to modulate the apoptosis, and to accomplish it; viruses encode proteins which specifically interact with the cellular signaling pathways. While some viruses encode proteins, which inhibit the apoptosis or death of the infected cells, there are viruses whose encoded proteins can kill the infected cells by multiple mechanisms, including apoptosis. A particular class of these viruses has specific gene(s) in their genomes which, upon ectopic expression, can kill the tumor cells selectively without affecting the normal cells. These genes and their encoded products have demonstrated great potential to be developed as novel anticancer therapeutic agents which can specifically target and kill the cancer cells leaving the normal cells unharmed. In this review, we will discuss about the viral genes having specific cancer cell killing properties, what is known about their functioning, signaling pathways and their therapeutic applications as anticancer agents.

show abstract

“…However, when expressed alone at high levels, E4orf4 induces the selective p53-independent death of a variety of human tumor cells (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21) and is toxic in the yeast Saccharomyces cerevisiae (22)(23)(24)(25)(26)(27)(28)(29). Killing of cancer cells by E4orf4 is dose dependent and resembles apoptosis in some cell lines, but it seems to occur by mitotic catastrophe in others (8-13, 15, 30, 31).…”

mentioning

confidence: 99%

“…To date, several E4orf4 interacting partners besides PP2A have been reported and, in some cases, suggested to contribute to E4orf4-induced cell death, including c-Src (12,18,31,(70)(71)(72)(73)(74), the ATP-dependent chromatin-remodeling factor ACF (3), the NTPDASE4 gene product Golgi UDPase (20,29), and Nup 205 (2). In an attempt to discover more E4orf4 binding partners, we performed affinity purification/mass spectrometry (AP-MS) using both wild-type E4orf4 and class I and class II E4orf4 mutants.…”

mentioning

confidence: 99%

The Human Adenovirus Type 5 E4orf4 Protein Targets Two Phosphatase Regulators of the Hippo Signaling Pathway

Mui

Zhou

Blanchette

et al. 2015

J Virol

View full text Add to dashboard Cite

When expressed alone at high levels, the human adenovirus E4orf4 protein exhibits tumor cell-specific p53-independent toxicity. A major E4orf4 target is the B55 class of PP2A regulatory subunits, and we have shown recently that binding of E4orf4 inhibits PP2A B55 phosphatase activity in a dose-dependent fashion by preventing access of substrates (M. Z. Mui et al., PLoS Pathog 9:e1003742, 2013, http://dx.doi.org/10.1371/journal.ppat.1003742). While interaction with B55 subunits is essential for toxicity, E4orf4 mutants exist that, despite binding B55 at high levels, are defective in cell killing, suggesting that other essential targets exist. In an attempt to identify additional targets, we undertook a proteomics approach to characterize E4orf4-interacting proteins. Our findings indicated that, in addition to PP2A B55 subunits, ASPP-PP1 complex subunits were found among the major E4orf4-binding species. Both the PP2A and ASPP-PP1 phosphatases are known to positively regulate effectors of the Hippo signaling pathway, which controls the expression of cell growth/survival genes by dephosphorylating the YAP transcriptional coactivator. We find here that expression of E4orf4 results in hyperphosphorylation of YAP, suggesting that Hippo signaling is affected by E4orf4 interactions with PP2A B55 and/or ASPP-PP1 phosphatases. Furthermore, knockdown of YAP1 expression was seen to enhance E4orf4 killing, again consistent with a link between E4orf4 toxicity and inhibition of the Hippo pathway. This effect may in fact contribute to the cancer cell specificity of E4orf4 toxicity, as many human cancer cells rely heavily on the Hippo pathway for their enhanced proliferation. IMPORTANCEThe human adenovirus E4orf4 protein has been known for some time to induce tumor cell-specific death when expressed at high levels; thus, knowledge of its mode of action could be of importance for development of new cancer therapies. Although the B55 form of the phosphatase PP2A has long been known as an essential E4orf4 target, genetic analyses indicated that others must exist. To identify additional E4orf4 targets, we performed, for the first time, a large-scale affinity purification/mass spectrometry analysis of E4orf4 binding partners. Several additional candidates were detected, including key regulators of the Hippo signaling pathway, which enhances cell viability in many cancers, and results of preliminary studies suggested a link between inhibition of Hippo signaling and E4orf4 toxicity.

show abstract

NTPDASE4 Gene Products Cooperate with the Adenovirus E4orf4 Protein through PP2A-Dependent and -Independent Mechanisms and Contribute to Induction of Cell Death

Cited by 8 publications

References 41 publications

Biphasic Functional Interaction between the Adenovirus E4orf4 Protein and DNA-PK

Biphasic Functional Interaction between the Adenovirus E4orf4 Protein and DNA-PK

Viral genes as oncolytic agents for cancer therapy

The Human Adenovirus Type 5 E4orf4 Protein Targets Two Phosphatase Regulators of the Hippo Signaling Pathway

Contact Info

Product

Resources

About