Open AccessIdentification and Characterization of the Product Encoded by ORF69 of Kaposi's Sarcoma-Associated Herpesvirus
Author(s) -
Roberta Santarelli,
Antonella Farina,
Marisa Granato,
Roberta Gonnella,
Salvatore Raffa,
Luisa Leone,
Roberto Bei,
Andrea Modesti,
Luigi Frati,
Maria Rosaria Torrisi,
Alberto Faggioni
Publication year - 2008
Publication title -
journal of virology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.617
H-Index - 292
eISSN - 1070-6321
pISSN - 0022-538X
DOI - 10.1128/jvi.02400-07
Subject(s) - biology , nuclear membrane , kaposi's sarcoma associated herpesvirus , nuclear protein , immunoelectron microscopy , nuclear localization sequence , cell nucleus , lytic cycle , virus , virology , microbiology and biotechnology , gene product , open reading frame , viral matrix protein , gammaherpesvirinae , gene , peptide sequence , gene expression , herpesviridae , nucleus , genetics , antibody , transcription factor , viral disease
We report the identification and characterization of p33, the product of Kaposi's sarcoma-associated herpesvirus (KSHV) open reading frame 69 (ORF69), a positional homolog of the conserved herpesvirus protein UL31. p33 is expressed upon induction of viral lytic cycle with early kinetics. Immunofluorescence analysis revealed that in infected cell lines, the protein is localized in the nucleus, both in dotted spots and along the nuclear membrane. Nuclear fractionation experiments showed that p33 partitions with the nuclear matrix, and both immunoblotting of purified virions and immunoelectron microscopy indicated that the novel protein is not a component of the mature virus. Following ectopic expression in KSHV-negative cells, the protein was never associated with the nuclear membrane, suggesting that p33 needs to interact with additional viral proteins to reach the nuclear rim. In fact, after cotransfection with the ORF67 gene, the KSHV positional homolog of UL34, the p33 intranuclear signal changed and the two proteins colocalized on the nuclear membrane. A similar result was obtained when ORF69 was cotransfected with BFRF1, the Epstein-Barr virus (EBV) positional homolog of UL34 and ORF67. Finally, upon cotransfection, ORF69 significantly increased nuclear membrane reduplications induced by BFRF1. The above results indicate that KSHV p33 shares many similarities with its EBV homolog BFLF2 and suggest that functional cross-complementation is possible between members of the gammaherpesvirus subfamily.