Evolution of nuclear localization and functional interactions of the latency-associated nuclear antigens of KSHV and related macaque rhadinoviruses

• Main Author: Cherezova, Lidia
• Format: Dissertation
• Language: English
• Published: ProQuest Dissertations & Theses 01-01-2011
• Subjects: Cellular biology; Virology
• ISBN: 9781124599953; 1124599959

Kaposi's sarcoma associated herpesvirus (KSHV) is the causative agent of Kaposi's sarcoma, primary effusion lymphoma and multicentric Castleman's disease and is classified as a rhadinovirus. Two lineages of related rhadinoviruses are found in macaques. The RV1 lineage includes retroperitoneal fibromatosis associated herpesvirus (RFHV), the macaque homolog of KSHV, which is associated with a Kaposi's sarcoma-like tumor. The distantly-related RV2 lineage includes rhesus rhadinovirus (RRV), which is associated with lymphoma and lymphoproliferative disorders in macaques. The mechanism of tumorigenesis mediated by these viruses is poorly understood. The latency-associated nuclear antigen (LANA) plays an important role in this process. In KSHV, LANA is essential for the establishment and maintenance of latency, the program of infection associated with tumorigenesis, as it inhibits the cellular tumor suppressors, p53 and pRB. Our studies show that the ability to downregulate p53 is conserved between KSHV and RFHV LANA, indicating similarities in the tumorigenic properties of the RV1 rhadinoviruses. RRV LANA lacks the ability to interact with and inhibit p53, indicating a strong evolutionary difference in functionality of the RV1 and RV2 lineages. Since nuclear localization of LANA is critical for its role in latency and ability to subvert normal cellular functions, we examined the ability of the RV1 and RV2 LANAs to interact and utilize the cellular nuclear import pathways. We demonstrate that KSHV and RFHV LANA, like p53, contain a lysine/arginine-rich bipartite nuclear localization signal (NLS) that interacts with importin a within the classical nuclear import pathway. We also demonstrate that unlike p53, the bipartite classical NLS of KSHV and RFHV LANA is embedded within an arginine/glycine-rich NLS that interacts with importin β1 within the non-classical nuclear import pathway. This arginine/glycine-rich NLS is conserved in RRV LANA, which only utilizes the non-classical import pathway. Our studies suggest that the common use of the classical import pathway plays a role in the nuclear co-localization and interaction of p53 and the RV1 LANAs. Furthermore, the use of the non-classical nuclear import pathway by both RV1 and RV2 viruses suggests additional conserved functional interactions with nuclear components that may also play a role in tumorigenesis.