Carboxy terminus of human herpesvirus 8 latency-associated nuclear antigen mediates dimerization, transcriptional repression, and targeting to nuclear bodies.
Human herpesvirus 8 (HHV-8; also known as Kaposi's sarcoma-associated herpesvirus) is the causative agent of Kaposi's sarcoma and certain B-cell lymphomas. In most infected cells, HHV-8 establishes a latent infection characterized by the expression of latency-associated nuclear antigen (LANA) encoded by open reading frame 73. Although unrelated by sequence, there are functional similarities between LANA and the EBNA-1 protein of Epstein-Barr virus. Both accumulate as subnuclear speckles and are required for maintenance of the viral episome. EBNA-1 also regulates viral gene expression and is required for cell immortalization, suggesting that LANA performs similar functions in the context of HHV-8 infection. Here we show that LANA forms stable dimers, or possibly higher-order multimers, and that this is mediated by a conserved region in the C terminus. By expressing a series of truncations, we show that both the N- and C-terminal regions localize to the nucleus, although only the C terminus accumulates as nuclear speckles characteristic of the intact protein. Lastly, we show that LANA can function as a potent transcriptional repressor when tethered to constitutively active promoters via a heterologous DNA-binding domain. Domains in both the N and C termini mediate repression. This suggests that one function of LANA is to suppress the expression of the viral lytic genes or cellular genes involved in the antiviral response.
Schwam
D R
DR
Department of Microbiology and Kaplan Comprehensive Cancer Center, New York University School of Medicine, New York, New York 10016, USA.
Luciano
R L
RL
Mahajan
S S
SS
Wong
L
L
Wilson
A C
AC
D000595:Amino Acid Sequence; D000956:Antigens, Viral / Q000378:metabolism* / Q000502:physiology; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism / Q000648:ultrastructure; D017124:Conserved Sequence; D019281:Dimerization; D015967:Gene Expression Regulation, Viral; D017930:Genes, Reporter; D019288:Herpesvirus 8, Human / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure; D006801:Humans; D015151:Immunoblotting; D008156:Luciferases / Q000235:genetics; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000378:metabolism* / Q000502:physiology; D016415:Sequence Alignment; D014158:Transcription, Genetic; D014771:Virion / Q000235:genetics / Q000502:physiology / Q000648:ultrastructure
D000956:Antigens, Viral; D009687:Nuclear Proteins; C109540:latency-associated nuclear antigen; D008156:Luciferases