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- Mattsson, K, et al.
(författare)
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Latent nuclear antigen of Kaposi's sarcoma herpesvirus/human herpesvirus-8 induces and relocates RING3 to nuclear heterochromatin regions
- 2002
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Ingår i: The Journal of general virology. - : Microbiology Society. - 0022-1317 .- 1465-2099. ; 83:Pt 1, s. 179-188
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Tidskriftsartikel (refereegranskat)abstract
- LANA, the major latency-associated nuclear antigen of Kaposi’s sarcoma herpesvirus/human herpesvirus-8 (KSHV/HHV-8), binds RING3 protein, one of five human homologues of thefsh(female sterile homeotic) gene product ofDrosophila. In KSHV/HHV-8-infected cells LANA and the viral episomes accumulate in heterochromatin-associated nuclear bodies. Here we show that in several KSHV/HHV-8-negative cell lines derived from carcinomas, sarcomas and lymphomas, RING3 was expressed at low levels, primarily localized to the euchromatin, and dissociated from the chromosomes during mitosis. In contrast, in KSHV/HHV-8-infected body cavity lymphoma cells the bulk of RING3 localizes to the LANA nuclear bodies and remains associated with the chromosomes during cell division. KSHV/HHV-8-infected body cavity lymphoma cells expressed RING3 at much higher levels than cells without the virus. Transfection of full-length LANA, but not the C terminus alone, greatly induced RING3 gene expression, and LANA and RING3 co-localized even in the transfected cells, in the absence of KSHV/HHV-8 viral DNA. High levels of LANA expression led to the disappearance of heterochromatin in both human and mouse cells. We suggest that LANA and RING3 may create a local euchromatic microenvironment around the viral episomes that are anchored to the heterochromatin.
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- Pokrovskaja, K, et al.
(författare)
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Proteasome inhibitor induces nucleolar translocation of Epstein-Barr virus-encoded EBNA-5
- 2001
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Ingår i: The Journal of general virology. - : Microbiology Society. - 0022-1317 .- 1465-2099. ; 82:Pt 2, s. 345-358
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Tidskriftsartikel (refereegranskat)abstract
- We have previously shown that Epstein–Barr virus (EBV)-encoded EBNA-5 is localized to PML bodies (PODs) in EBV-immortalized lymphoblastoid cell lines (LCLs). Here we have extended our study of the subnuclear localization of EBNA-5 and found a strict co-localization with PML in LCLs and in BL lines with an immunoblastic, LCL-like phenotype. Moreover, GFP–EBNA-5 accumulated in PML bodies upon transfection into LCLs. In contrast, transfection of cell lines of non-immunoblastic origin with an EBNA-5 expression construct showed preferential localization of the protein to the nucleoplasm. Since PML is involved in proteasome-dependent protein degradation, we investigated the total levels and sub-cellular localization of EBNA-5 upon inhibition of proteasome activity. We found that a proteasome inhibitor, MG132, induced the translocation of both endogenous and transfected EBNA-5 to the nucleoli in every cell line tested. The total EBNA-5 protein levels were not affected by the proteasomal block. EBNA-5 forms complexes with heat shock protein Hsp70. The proteasome inhibitor induced a rise in total levels of Hsp70 and dramatically changed its homogeneous nuclear and cytoplasmic distribution into nucleolar and cytoplasmic. This effect was EBNA-5-independent. The nucleolar localization of Hsp70 was enhanced by the presence of EBNA-5, however. EBNA-5 also enhanced the nucleolar translocation of a mutant p53 in a colon cancer line, SW480, treated with MG132. The coordinated changes in EBNA-5 and Hsp70 localization and the effect of EBNA-5 on mutant p53 distribution upon MG132 treatment might reflect the involvement of EBNA-5 in the regulation of intracellular protein trafficking associated with the proteasome-mediated degradation.
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