Transcriptional activation by the Kaposi's sarcoma-associated herpesvirus latency-associated nuclear antigen is facilitated by an N-terminal chromatin-binding motif.
In immunocompromised patients, infection with Kaposi's sarcoma-associated herpesvirus (KSHV) can give rise to Kaposi's sarcoma and several lymphoproliferative disorders. In these tumors, KSHV establishes a latent infection in many of the rapidly proliferating and morphologically abnormal cells. Only a few viral gene products are expressed by the latent virus, and one of the best characterized is the latency-associated nuclear antigen (LANA), a nuclear protein required for the maintenance of viral episomal DNA in the dividing host cell. LANA can also activate or repress an assortment of cellular and viral promoters and may contribute to pathogenesis by allowing the proliferation and survival of host cells. Here we show that activation of the human E2F1 and cyclin-dependent kinase-2 (CDK2) promoters requires elements from both the N- and C-terminal regions of LANA. Deletion of the first 22 amino acids, which are necessary for episome tethering, does not affect nuclear localization but significantly reduces transactivation. Within the deleted peptide, we have identified a short sequence, termed the chromatin-binding motif (CBM), that binds tightly to interphase and mitotic chromatin. A second chromatin-binding activity resides in the C terminus but is not sufficient for optimal transactivation. Alanine substitutions within the CBM reveal a close correlation between the transactivation and chromatin binding activities, implying a mechanistic link. In contrast to promoter activation, we find that the 223 amino acids of the LANA C terminus are sufficient to inhibit p53-mediated activation of the human BAX promoter, indicating that the CBM is not required for all transcription-related functions.
Wong
Lai-Yee
LY
Department of Microbiology, New York University School of Medicine, 550 First Ave., New York, NY 10016, USA.
Matchett
Gerald A
GA
Wilson
Angus C
AC
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000956:Antigens, Viral / Q000235:genetics*; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D002460:Cell Line; D002843:Chromatin / Q000235:genetics / Q000378:metabolism; D004279:DNA, Viral / Q000235:genetics; D006367:HeLa Cells; D006566:Herpesviridae Infections / Q000209:etiology / Q000276:immunology / Q000821:virology; D019288:Herpesvirus 8, Human / Q000737:chemistry / Q000235:genetics* / Q000276:immunology; D006801:Humans; D007399:Interphase; D008954:Models, Biological; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009687:Nuclear Proteins / Q000737:chemistry / Q000235:genetics* / Q000276:immunology; D015533:Transcriptional Activation; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
D000956:Antigens, Viral; D002843:Chromatin; D004279:DNA, Viral; D009687:Nuclear Proteins; D016159:Tumor Suppressor Protein p53; C109540:latency-associated nuclear antigen