Two major outer envelope glycoproteins of Epstein-Barr virus are encoded by the same gene

Abstract

Two major outer envelope glycoproteins of Epstein-Barr virus, gp350 and gp220, are known to be encoded by 3.2- and 2.5-kilobase RNAs which map to the same DNA fragment (M. Hummel, D. Thorley-Lawson, and E. Kieff, J. Virol. 49:413-417). These RNAs have the same 5' and 3' ends. The larger RNA is encoded by a 2,777-base DNA segment which is preceded by TATTAAA, has AATAAA near its 3' end, and contains a 2,721-base open reading frame. The smaller RNA has one internal splice which maintains the same open reading frame. Translation of the 3.2- and 2.5-kilobase RNAs yielded proteins of 135 and 100 kilodaltons (Hummel et al., J. Virol. 49:413-417). The discrepancy between the 907 codons of the open reading frame and the 135-kilodalton size of the gp350 precursor is due to anomalous behavior of the protein in gel electrophoresis, since a protein translated from most of the Epstein-Barr virus open reading frame in Escherichia coli had similar properties. Antisera raised in rabbits to the protein expressed in E. coli specifically immunoprecipitated gp350 and gp220, confirming the mapping and sequencing results and the translational reading frame. The rabbit antisera also reacted with the plasma membranes of cells that were replicating virus and neutralized virus, particularly after the addition of complement. This is the first demonstration that the primary amino acid sequence of gp350 and gp220 has epitopes which can induce neutralizing antibody. We propose a model for the gp350 protein based on the theoretical analysis of its primary sequence.