Detection of Dengue 4 Virus Core Protein in the Nucleus. I. A Monoclonal Antibody to Dengue 4 Virus Reacts with the Antigen in the Nucleus and Cytoplasm

Abstract

SUMMARYA mouse monoclonal antibody (MAb) to dengue 4 (DEN-4) virus reacted with the antigen in the nucleus as well as in the cytoplasm of DEN-4-infected mammalian and mosquito cells, as demonstrated by the peroxidase-antiperoxidase staining method. The intranuclear antigen appeared to accumulate at the nucleoli, forming spots, whereas the cytoplasmic antigen appeared to be localized mainly in large perinuclear loci in the infected cells. The MAb-reactive antigen was produced in the presence of actinomycin D, which caused the accumulation in the nucleus to be altered to a dispersed pattern. Radioimmunoprecipitation analysis of [35S]methionine-labelled purified virions and Western blot analysis of the antigens prepared from the infected mammalian and mosquito cells showed that the MAb was directed against the DEN-4 virus core protein (M~ 15-5K). These results indicated that the DEN-4 virus core protein was partially transported, soon after its synthesis in the cytoplasm, into the nucleus and accumulated at the nucleoli.

Multiple regions in dengue virus capsid protein contribute to nuclear localization during virus infection

“…It was remarkable that, whilst dengue virus was able to replicate efficiently in the three cell lines employed, nuclear localization of C protein was not uniformly present in these cell lines. Our observations of C protein localization to the nucleolus in the two infected mammalian cell lines were similar to those of Tadano et al (1989) and Wang et al (2002), and also concurred with the findings of Bulich & Aaskov (1992) that C protein nucleolar localization in C6/36 cells is a rare event.…”

“…Kinetics of C protein localization to nuclei and nucleoli of dengue virus-infected cells Several investigators have reported different patterns of dengue virus and other flavivirus C protein nuclear localization, or lack thereof, in many cell lines, which may reflect cellular differences and methodological variations (Tadano et al, 1989;Bulich & Aaskov, 1992;Westaway et al, 1997;Ng et al, 2001;Wang et al, 2002;Mori et al, 2005;Oh et al, 2006). To affirm the phenomenon in this study, subcellular localization of dengue virus C protein was assessed during infection of two mammalian cell lines (PS and Vero) and a mosquito cell line (C6/36) with a dengue serotype 2 virus, strain 16681, by using indirect IFA.…”

“…1(d) shows examples of cytoplasmic only and cytoplasmic plus nuclear staining in all three cell types tested. Other fixation and permeabilization methods, including cold acetone fixation (Bulich & Aaskov, 1992), methanol fixation (Tadano et al, 1989) and formaldehyde fixation followed by methanol treatment (Westaway et al, 1997), were attempted with PS and C6/36 cells. All gave similar staining patterns, but with less clarity (data not shown).…”

“…During dengue virus serotype 2 and 4 infection, C protein is also found in the nuclei and nucleoli of many infected cell lines (Tadano et al, 1989;Bulich & Aaskov, 1992;Wang et al, 2002). This feature appears to be conserved among flaviviruses, as other investigators have detected C proteins of Kunjin virus, West Nile virus and Japanese encephalitis virus (JEV) in both the cytoplasm and nuclei of infected mammalian cells (Westaway et al, 1997;Mori et al, 2005;Oh et al, 2006).…”

Comparative Analysis of Full-Length Genomic Sequences of 10 Dengue Serotype 1 Viruses Associated with Different Genotypes, Epidemics, and Disease Severity Isolated in Thailand over 22 Years

“…Although DENV C protein is responsible for encapsidation of viral RNA, which takes place in the cytoplasm of host cells, it also has been detected in the cytoplasm and nucleus 25,26 and perhaps in the nucleolus of infected cells. 27 Three putative nuclear-localization signal motifs of DENV have been predicted at residues 6-9 (motif I), 73-76 (motif II), and 85-100 (motif III) of C protein. 28 The function of the C protein in the nucleus remains to be investigated, but it has been hypothesized that the DENV C protein services as a transcription modulator similar to the core protein of hepatitis C virus, 9 which is involved in regulating the life cycle of DENV and is a building block of the virus.…”