Identification and characterization of an Epstein-Barr virus early antigen that is encoded by the NotI repeats

Abstract

The Epstein-Barr virus (EBV} genome is characterized by two regions carrying partially homologous clusters of short tandem repeats (NotI and PstI repeats) flanked by 1,044 and 1,045 base pairs with almost perfect homology (DL and DR, left and right duplications, respectively). Both repetitive regions are transcribed into poly(A)+ mRNA after induction of the productive EBV cycle with the tumor promoter 12-O-tetradecanoylphorbol-13-acetate and contain open reading frames. To identify the potential protein encoded by the NotI repeat open reading frame (BHLFl), two repeat units of EBV strain M-ABA were expressed using the tryptophan-regulated Escherichia coli expression vector pATH1l. Rabbit antisera generated against the resulting fusion protein reacted specifically with a protein varying in molecular size between 70,000 and 90,000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, found after 12-O-tetradecanoyl-phorbol-13acetate or n-butyrate induction in various cell lines harboring EBV. In immunofluorescence tests with the BHLFl-specific antiserum, an immunofluorescence with EA-D specificity could be observed. In addition, the BHLF1 protein is exhibiting polyanion-binding activity with a maximum for single-stranded DNA. Furthermore, the fusion protein is recognized by a number of human EBV-positive sera.

Promiscuous expression of Epstein‐Barr virus genes in Burkitt's lymphoma from the central African country Malawi

“…1). Representative ISH data are shown in Figure 3 (top panels b , c ), supporting the high degree of variability seen in gene expression among samples and the nuclear location of this antigen 20. The difference between the RT‐PCR and ISH numbers may reflect the enhanced sensitivity of the former technique or degradation (possibly selected) of RNA during storage of methanol‐fixed samples.…”

“…Not a great deal is known about several of the genes expressed in the eBLs at high frequencies, notably the early IR2 (BHLF1) and IR4 (LF3) genes, as well as BARF1 and the CSTs/BARTs (Table II). Both of the early genes are thought to be associated with lytic replication and the IR2 protein,20 but not the IR4 protein,12 has been identified as binding to DNA. The transcripts of both genes, by virtue of their high GC contents, are highly structured; and that of IR4, acting possibly as a double‐stranded RNA, can influence the sensitivity of cells to α‐interferons 27, 28.…”

Translational profiling of B cells infected with the Epstein-Barr virus reveals 5′ leader ribosome recruitment through upstream open reading frames

“…( 30 , 32 , 33 ). There is one report of BHLF1 protein expression in induced EBV-infected cells ( 46 ). Interestingly, BHLF1 protein expression in that case included abundant degradation products.…”

Immediate Early and Early Lytic Cycle Proteins Are Frequent Targets of the Epstein-Barr Virus–induced Cytotoxic T Cell Response

“…Of the antigens tested, BZLF1 and BRLF1 are the best known immediate early proteins and are expressed at the very initiation of lytic cycle ( 25 , 26 ). Together these activate the expression of at least four of the early proteins studied here, namely BMLF1, itself a transactivator ( 44 ), BMRF1, a processivity factor involved in viral DNA replication ( 45 ), BHLF1, an early antigen EA-D component of unknown function ( 46 ), and BHRF1, the viral homologue of cellular Bcl-2 ( 47 ); the two other early proteins, BALF2 and BALF5, are also involved in viral DNA replication as the major DNA binding protein and the viral DNA polymerase, respectively ( 23 ). The only evidence to date that any of these early proteins contain T cell epitopes is the identification of a HLA class II–restricted response to BHRF1 in an IM patient ( 48 ).…”