Down-regulation of proteolytic complexes following EBV activation in BL cells

Department of Public Health Sciences, University "La Sapienza", P. le A. Moro 5, 00185 Rome, Italy.
Biochemical and Biophysical Research Communications (Impact Factor: 2.3). 02/2007; 352(4):947-52. DOI: 10.1016/j.bbrc.2006.11.127
Source: PubMed


In Burkitt's lymphoma cells, Epstein Barr virus (EBV) latency products interact with the ubiquitin-proteasome system to promote episomal maintenance and immunological evasion while the tripeptidylpeptidase II (TPPII) functions as an alternative protease. In the present study, we have examined the activities and levels of the proteasome and TPPII complex in Raji and in Akata cells after induction of EBV lytic cycle. The results show that the chymotrypsin-like and caspase-like activities of the proteasome were substantially reduced in Raji and Akata cells. Similarly, TPPII activity was diminished in both cell lines but was recovered in Akata cells at longer time after induction. Protein levels of the alpha/beta subunits of the 20S proteasome and TPPII concentration decreased to different extents after EBV activation, whereas the ubiquitin binding S6' subunit of the 19S regulatory complex increased three to fourfold along with the levels of ubiquitin-conjugates. Collectively, these observations demonstrate impairment of two major cellular proteolytic systems at the onset of EBV lytic infection.

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Available from: Giulia Matusali, Nov 19, 2014
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    • "At different times, samples of cells, untreated or treated with EBV lytic cycle activators, were collected and the lysates tested to measure the enzymatic activities or the subunit composition of the proteasome. The results concerning the evaluation of chymotrypsin-, trypsin-and caspase-like activities confirmed those previously reported (Matusali et al., 2007). To evaluate changes in the components of the proteolytic complex, we studied by immunoblot analysis the levels of constitutive (b1, b2 and b5) and IFNg-inducible (b1i, b2i and b5i) catalytic subunits of the 20S complex, as well as the expression of the PA28a, PA28b and PA28g proteins, following exposure of the cells to EBV inducing compounds. "
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    ABSTRACT: We have shown that Epstein-Barr virus (EBV) lytic cycle activation in Burkitt's lymphoma (BL) cells down-regulates chymotrypsin- and caspase-like activities of the proteasome. The aim of the present study was to evaluate whether EBV activation might also affect proteasome subunit composition. Our results indicate that, independently of the latency program established in the host cells, induction of the EBV lytic cycle reduces the expression of the proteasomal components β5, β1 and β2i, whereas it increases that of β2, β1i, PA28α and PA28β. The modulation of the composition and enzymatic activities of the proteolytic complex are indicative of a less efficient generation of viral immunoepitopes.
    Full-text · Article · Sep 2010 · Biological Chemistry
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    • "At the indicated times, samples (about 106 cells) were collected, washed and lysed as described [38]. 30 μg of proteins, as determined by a modified Lowry assay (RC DC protein assay, BioRad), were resolved by SDS-PAGE on a 10% gel and transferred onto nitrocellulose membrane. "
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    ABSTRACT: Poly(ADP-ribosylation) is a post-translational modification of nuclear proteins involved in several cellular events as well as in processes that characterize the infective cycle of some viruses. In the present study, we investigated the role of poly(ADP-ribosylation) on Epstein-Barr Virus (EBV) lytic cycle activation. Inhibition of PARP-1 by 3-aminobenzamide (3-ABA) during EBV induction, diminished cell damage and apoptosis in the non-productive Raji cell line while markedly reducing the release of viral particles in the productive Jijoye cells. Furthermore, incubation with 3-ABA up-regulated the levels of LMP1 and EBNA2 latent viral proteins. At the same time, it slightly affected the expression of the immediate early BZLF1 gene, but largely down-regulated the levels of the early BFRF1 protein. The modulation of the expression of both latent and lytic EBV genes appeared to be post-transcriptionally regulated. Taken together the data indicate that PARP-1 plays a role in the progression of EBV lytic cycle and therefore, PARP inhibitors might represent suitable pharmacological adjuncts to control viral spread in EBV productive infection.
    Full-text · Article · Feb 2007 · Infectious Agents and Cancer