Regulation and Autoregulation of the Promoter for the Latency-associated Nuclear Antigen of Kaposi's Sarcoma-associated Herpesvirus

Abstract

Kaposi's sarcoma-associated herpesvirus (KSHV) or human herpesvirus 8 has been established as the etiological agent of Kaposi's sarcoma and certain AIDS-associated lymphomas. KSHV establishes latent infection in these tumors, invariably expressing high levels of the viral latency-associated nuclear antigen (LANA) protein. LANA is necessary and sufficient to maintain the KSHV episome. It also modulates viral and cellular transcription and has been implicated directly in oncogenesis because of its ability to bind to the p53 and pRb tumor suppressor proteins. Previously, we identified the LANA promoter (LANAp) and showed that it was positively regulated by LANA itself. Here, we present a detailed mutational analysis and define cis-acting elements and trans-acting factors for the core LANAp. We found that a downstream promoter element, TATA box, and GC box/Sp1 site at ؊29 are all individually required for activity. This architecture places LANAp into the small and unusual group of eukaryotic promoters that contain both the downstream promoter element and TATA element but lack a defined initiation site. Furthermore, we demonstrate that LANA regulates its own promoter via its C-terminal domain and does bind to a defined site within the core promoter.

Kaposi's sarcoma-associated herpesvirus LANA recruits the DNA polymerase clamp loader to mediate efficient replication and virus persistence

“…Both N-terminal LANA (N-LANA) and C-terminal LANA (C-LANA) are essential for function. N-LANA associates with mitotic chromosomes via binding histones H2A/H2B, and C-LANA simultaneously binds KSHV terminal repeat (TR) DNA (7,(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20). Thus, LANA tethers the viral genome to host chromosomes and distributes viral DNA to daughter nuclei during mitosis.…”

CTCF Regulates Kaposi's Sarcoma-Associated Herpesvirus Latency Transcription by Nucleosome Displacement and RNA Polymerase Programming

“…Transcription initiation has been mapped to a single major start site that functions largely through a strong core initiator element, with no apparent enhancer or upstream promoter regulatory factors (11,12). The initiation site of the latency transcript lies within the 5= untranslated region (UTR) of the complementary strand transcript for K14/ORF74 (viral G protein-coupled receptor [vGPCR]), which is expressed primarily in lytically induced B cells but is also detected in most KSHV-infected tissues and has been implicated in the pathogenesis of KS (17)(18)(19)(20)(21).…”

“…The latency transcripts have complex structures, with multicistronic messages and several alternative promoters, as well as lytic gene promoters for both sense and antisense orientations. Proper regulation of these various transcripts is essential for viral persistence and host cell survival.Transcriptional regulation and mRNA processing of the KSHV major latency transcripts have been investigated in some detail (8,9,(11)(12)(13)(14)(15)(16). Transcription initiation has been mapped to a single major start site that functions largely through a strong core initiator element, with no apparent enhancer or upstream promoter regulatory factors (11,12).…”

Kaposi's sarcoma herpesvirus-encoded latency-associated nuclear antigen stabilizes intracellular activated Notch by targeting the Sel10 protein

“…In KSHV-infected tumors, LANA is a predominant latent protein and exhibits multiple functions related to viral genome replication, transcription regulation, and cell proliferation (10,14,32). It has been shown that LANA autoactivates its own promoter; thus, the expression of LANA is maintained consistently at a high level by the regulation of this positive-feedback loop (33). High expression of LANA in KSHV-infected cells is one strategy for the virus to establish and maintain latent infection because down regulation of LANA expression results in disruption of viral latency (34)(35)(36).…”