Structure and function of latency-associated nuclear antigen.
Latency-associated nuclear antigen (LANA) encoded by open reading frame 73 (ORF73) is the major latent protein expressed in all forms of KSHV-associated malignancies. LANA is a large (222-234 kDa) nuclear protein that interacts with various cellular as well as viral proteins. LANA has been classified as an oncogenic protein as it dysregulates various cellular pathways including tumor suppressor pathways associated with pRb and p53 and can transform primary rat embryo fibroblasts in cooperation with the cellular oncogene Hras. It associates with GSK-3beta, an important modulator of Wnt signaling pathway leading to the accumulation of cytoplasmic beta-catenin, which upregulates Tcf/Lef regulated genes after entering into the nucleus. LANA also blocks the expression of RTA, the reactivation transcriptional activator, which is critical for the latency to lytic switch, and thus helps in maintaining viral latency. LANA tethers the viral episomal DNA to the host chromosomes by directly binding to its cognate binding sequence within the TR region of the genome through its C terminus and to the nucleosomes through the N terminus of the molecule. Tethering to the host chromosomes helps in efficient partitioning of the viral episomes in the dividing cells. Disruptions of LANA expression led to reduction in the episomal copies of the viral DNA, supporting its role in persistence of the viral DNA. The functions known so far suggest that LANA is a key player in KSHV-mediated pathogenesis.
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Department of Microbiology and Tumor Virology Program of the Abramson Comprehensive Cancer Center, University of Pennsylvania School of Medicine, 201E Johnson Pavilion, 3610 Hamilton Walk, Philadelphia, PA 19104, USA. erle@mail.med.upenn.edu
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D000818:Animals; D000956:Antigens, Viral / Q000737:chemistry* / Q000502:physiology*; D002453:Cell Cycle; D002454:Cell Differentiation; D004261:DNA Replication; D038362:Glycogen Synthase Kinase 3 / Q000502:physiology; D000071679:Glycogen Synthase Kinase 3 beta; D019288:Herpesvirus 8, Human / Q000472:pathogenicity*; D006801:Humans; D009687:Nuclear Proteins / Q000737:chemistry* / Q000502:physiology*; D010957:Plasmids; D012333:RNA, Messenger / Q000032:analysis; D016160:Retinoblastoma Protein / Q000037:antagonists & inhibitors; D016159:Tumor Suppressor Protein p53 / Q000502:physiology; D017735:Virus Latency; D014779:Virus Replication; D051176:beta Catenin / Q000502:physiology; D050880:p300-CBP Transcription Factors / Q000378:metabolism
D000956:Antigens, Viral; D009687:Nuclear Proteins; D012333:RNA, Messenger; D016160:Retinoblastoma Protein; D016159:Tumor Suppressor Protein p53; D051176:beta Catenin; C109540:latency-associated nuclear antigen; D050880:p300-CBP Transcription Factors; C000605506:GSK3B protein, human; D000071679:Glycogen Synthase Kinase 3 beta; C000605508:Gsk3b protein, rat; D038362:Glycogen Synthase Kinase 3