title: Serum-dependent expression of promyelocytic leukemia protein suppresses propagation of influenza virus.
abstract: The rate of propagation of influenza virus in human adenocarcinoma Caco-2 cells was found to negatively correlate with the concentration of fetal bovine serum (FBS) in the culture medium. Virus replicated more rapidly at lower FBS concentrations (0 or 2%) than at higher concentrations (10 or 20%) during an early stage of infection. Basal and interferon (IFN)-induced levels of typical IFN-inducible anti-viral proteins, such as 2',5'-oligoadenylate synthetase, dsRNA-activated protein kinase and MxA, were unaffected by variation in FBS concentrations. But promyelocytic leukemia protein (PML) was expressed in a serum-dependent manner. In particular, the 65 to 70 kDa isoform of PML was markedly upregulated following the addition of serum. In contrast, other isoforms were induced by IFN treatment, and weakly induced by FBS concentrations. Immunofluorescence microscopy indicated that PML was mainly formed nuclear bodies in Caco-2 cells at various FBS concentrations, and the levels of the PML-nuclear bodies were upregulated by FBS. Overexpression of PML isoform consisting of 560 or 633 amino acid residues by transfection of expression plasmid results in significantly delayed viral replication rate in Caco-2 cells. On the other hand, downregulation of PML expression by RNAi enhanced viral replication. These results indicate that PML isoforms which are expressed in a serum-dependent manner suppress the propagation of influenza virus at an early stage of infection.
authors.affiliation: Department of Microbiology, Sapporo Medical University School of Medicine, and Hokkaido Institute of Public Health, Kita-ku, Sapporo 060-0819, Japan.
authors.forename: Shigeo
authors.initials: S
authors.lastname: Iki
authors.forename: Shin-ichi
authors.initials: S
authors.lastname: Yokota
authors.forename: Tamaki
authors.initials: T
authors.lastname: Okabayashi
authors.forename: Noriko
authors.initials: N
authors.lastname: Yokosawa
authors.forename: Kyosuke
authors.initials: K
authors.lastname: Nagata
authors.forename: Nobuhiro
authors.initials: N
authors.lastname: Fujii
mesh_terms: D015088:2',5'-Oligoadenylate Synthetase / Q000032:analysis; D015153:Blotting, Western; D018938:Caco-2 Cells; D002467:Cell Nucleus / Q000737:chemistry; D003470:Culture Media / Q000737:chemistry; D019204:GTP-Binding Proteins / Q000032:analysis; D018628:Gene Dosage; D015870:Gene Expression; D020868:Gene Silencing; D006801:Humans; D009980:Influenza A virus / Q000502:physiology*; D007372:Interferons / Q000032:analysis; D008856:Microscopy, Fluorescence; D008970:Molecular Weight; D064547:Myxovirus Resistance Proteins; D009363:Neoplasm Proteins / Q000032:analysis / Q000502:physiology*; D009687:Nuclear Proteins / Q000032:analysis / Q000502:physiology*; D000071156:Promyelocytic Leukemia Protein; D020033:Protein Isoforms; D034622:RNA Interference; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D044967:Serum; D014157:Transcription Factors / Q000032:analysis / Q000502:physiology*; D025521:Tumor Suppressor Proteins / Q000032:analysis / Q000502:physiology*; D010948:Viral Plaque Assay; D014779:Virus Replication; D019892:eIF-2 Kinase / Q000032:analysis
chemical_list: D003470:Culture Media; C579071:MX1 protein, human; D064547:Myxovirus Resistance Proteins; D009363:Neoplasm Proteins; D009687:Nuclear Proteins; D000071156:Promyelocytic Leukemia Protein; D020033:Protein Isoforms; D012333:RNA, Messenger; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; C070576:PML protein, human; D007372:Interferons; D019892:eIF-2 Kinase; D015088:2',5'-Oligoadenylate Synthetase; D019204:GTP-Binding Proteins