Identification and Characterization of a 50K DNA-binding Protein of Guinea-pig Cytomegalovirus

Abstract

SUMMARYIn a previous study we showed that cells infected with guinea-pig cytomegalovirus (GPCMV) contain large amounts of a non-structural 50K nuclear protein that is detectable by immunoelectron microscopy using monoclonal antibodies. The present study shows that this 50K protein is a DNA-binding protein, as determined by singlestranded DNA affinity chromatography, and a phosphorylated protein as demonstrated by immunoprecipitation using [32P]orthophosphate_labelled cells. This protein binds both viral and host cellular double-stranded and single-stranded DNA, assayed by a simple method using DNA linked to a nylon membrane. Induction of the 50K protein in GPCMV-infected cells was highly dependent on viral DNA synthesis, which was detected by dot hybridization using a cloned GPCMV DNA probe. Synthesis of the 50K protein was significantly impaired when phosphonoacetic acid was added to the culture medium. Induction of the 50K protein was detected about 6 h before the appearance of the 76K viral matrix protein.

Subcellular distribution of the major immediate early proteins of human cytomegalovirus changes during infection

“…Although the biological significance of the redistribution of IEt proteins during HCMV infection is not known, in the late phase of infection these proteins may play some role other than in gene regulation. Nucleocapsids and cores in the nuclear inclusions were sometimes stained by either MAb e-8 or MAb E3; similar findings have been obtained using cells infected with guinea-pig CMV using an MAb specific for the 50K DNA-binding protein (Tsutsui et al, 1986;Nogami-Satake & Tsutsui, 1988). It may be possible that a small amount of virus-encoded nuclear protein can be incorporated into the nucleocapsids by chance during viral morphogenesis.…”

“…The coated membranes of the dense bodies in the extracellular spaces were also stained with both MAb e-8 and MAb E3 (Fig. 2d, e and inset), but were not stained by MAbs specific for the 50K DNA-binding protein of guinea-pig CMV (Nogami-Satake & Tsutsui, 1988) (Fig. 2c).…”

Pathogenesis of cytomegalovirus-associated labyrinthitis in a guinea pig model

“…1C). Taking into account the timing of DNA replication, it is likely that the 50 kD viral protein is an antigen that is expressed during an early phase of the infection, which is similar to that reported with MAb E-16 [28].…”

Immunoblot analysis of the humoral immune response to cytomegalovirus in non-pregnant and pregnant guinea pigs

“…Guinea pig CMV proteins, like those of human CMV, appear to be synthetized in infected cells in a regulated cascade of immediate early, early, and late viral proteins [15]. To date, only one guinea pig CMV protein, a non structural DNA binding protein with a molecular weight of 50 kDa has been characterized [20,22]. Further, the immunogenic proteins of guinea pig CMV have not been identified.…”