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Published on: July 6, 2013
Identification and expression of a murine cytomegalovirus early gene coding for an Fc receptor
R Thäle1, P Lucin, K Schneider
1Department of Virology, University of Heidelberg, Germany.
Insights
Researchers identified a new Fc receptor (FcR) gene in murine cytomegalovirus (MCMV). This discovery advances understanding of how herpesviruses interact with the immune system, specifically immunoglobulin G (IgG) binding.
Area of Science:
- Virology
- Immunology
- Molecular Biology
Background:
- Several herpesviruses, including cytomegalovirus, express receptors for the Fc domain of immunoglobulin G (IgG).
- Genes encoding these Fc receptors (FcR) were previously characterized only for alphaherpesviruses.
Purpose of the Study:
- To identify the gene responsible for the Fc receptor (FcR) in murine cytomegalovirus (MCMV).
- To characterize the protein product and its function as an FcR.
Main Methods:
- Precipitation of viral glycoproteins using the Fc fragment of IgG from infected cells.
- Deglycosylation to determine protein molecular mass.
- DNA injection and immunofluorescence microscopy to locate the coding region in the MCMV genome.
- Expression of the identified gene using recombinant vaccinia virus.
Main Results:
- Identification of a novel Fc receptor (FcR) gene, designated fcr1, within the MCMV genome.
- The gene encodes a glycoprotein (gp) of 569 amino acids, with expressed proteins of 86-88 kDa and 105 kDa exhibiting FcR properties.
- The identified gp shares sequence homology with gE proteins of other herpesviruses.
Conclusions:
- The study successfully identified and characterized the Fc receptor gene (fcr1) of murine cytomegalovirus (MCMV).
- This finding expands the understanding of FcR diversity among herpesviruses and their immune evasion strategies.
Abstract:
Several herpesviruses, including cytomegalovirus, induce receptors for the Fc domain of murine immunoglobulin G (IgG) molecules. Viral genes coding for these receptors have been characterized only for alphaherpesviruses. In this report, we describe a new approach that led to the identification of an Fc receptor (FcR) of murine cytomegalovirus (MCMV). The Fc fragment of IgG precipitated glycoproteins (gp) of 86 to 88 and 105 kDa from MCMV-infected cells. Deglycosylation by endoglycosidase F resulted in a protein with a molecular mass of 64 kDa. Injection of complete MCMV DNA or of DNA fragments, and the subsequent testing of cytoplasmic binding of IgG by immunofluorescence microscopy, was used to search for the coding region in the MCMV genome. The gene was located in the HindIII J fragment, map units 0.838 to 0.846, where an open reading frame of 1,707 nucleotides predicts a gp of 569 amino acids with a calculated molecular mass of 65 kDa. The sequence of this gp is related to those of the gE proteins of herpes simplex virus type 1 and varicella-zoster virus. The defined length of the mRNA, 1,838 nucleotides, was in agreement with that of a 1.9-kb RNA expressed throughout the replication cycle, starting at the early stages of infection. Expression of the gene fcr1 by recombinant vaccinia virus resulted in the synthesis of gp86/88 and gp105, each with FcR properties, and the correct identification of the gene encoding the FcR was confirmed by the DNA injection method.
