title: Processivity factor of KSHV contains a nuclear localization signal and binding domains for transporting viral DNA polymerase into the nucleus.
abstract: Kaposi's sarcoma-associated human herpesvirus (KSHV) encodes a processivity factor (PF-8, ORF59) that forms homodimers and binds to viral DNA polymerase (Pol-8, ORF9). PF-8 is essential for stabilizing Pol-8 on template DNA so that Pol-8 can incorporate nucleotides continuously. Here, the intracellular interaction of these two viral proteins was examined by confocal immunofluorescence microscopy. When individually expressed, PF-8 was observed exclusively in the nucleus, whereas Pol-8 was found only in the cytoplasm. However, when co-expressed, Pol-8 was co-translocated with PF-8 into the nucleus. Mutational analysis revealed that PF-8 contains a nuclear localization signal (NLS) as well as domains located at the N-terminus and the C-proximal regions that are required for Pol-8 binding. This study suggests that the mechanism that enables PF-8 to transport Pol-8 into the nucleus is the first critical step required for Pol-8 and PF-8 to function processively in KSHV DNA synthesis.
authors.affiliation: Department of Microbiology, School of Dental Medicine, University of Pennsylvania, Philadelphia, 19104, USA.
authors.forename: Yali
authors.initials: Y
authors.lastname: Chen
authors.forename: Mihai
authors.initials: M
authors.lastname: Ciustea
authors.forename: Robert P
authors.initials: RP
authors.lastname: Ricciardi
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002467:Cell Nucleus / Q000378:metabolism*; D002522:Chlorocebus aethiops; D003593:Cytoplasm / Q000378:metabolism; D017931:DNA Primers; D004261:DNA Replication; D004279:DNA, Viral / Q000235:genetics; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism*; D019084:Fluorescent Antibody Technique, Indirect; D019288:Herpesvirus 8, Human / Q000201:enzymology* / Q000235:genetics; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D021381:Protein Transport; D015398:Signal Transduction; D014162:Transfection; D014709:Vero Cells; D014764:Viral Proteins / Q000378:metabolism
chemical_list: D017931:DNA Primers; D004279:DNA, Viral; D014764:Viral Proteins; D004259:DNA-Directed DNA Polymerase