Antibodies against a synthetic peptide identify the Epstein-Barr virus-determined nuclear antigen

Proteins in normal and malignant cells, cross-reacting with the latent membrane protein encoded by Epstein-Barr virus

Human B lymphocytes transformed by infection with the Epstein-Barr virus (EBV) express a new membrane protein of 63 kDa (latent membrane protein, LMP) encoded by the virus. The function of this protein in the virus-cell interaction is not known. In this work we have identified in EBV- human and mouse cell molecules which cross-react with LMP. Two types of reagents were employed: (a) antibodies against LMP-derived synthetic peptides, affinity purified from antisera against a fusion protein containing the carboxy half of the LMP molecule and (b) antisera prepared by immunizing rabbits directly with the peptide conjugates. Cross-reactions were determined by radioimmunoblotting experiments. At least six molecules (Mr = 110, 85, 63, 53, 45 and 23 kDa), present in a variety of human cells (peripheral blood lymphocytes, B cell lines and epithelial cell lines) were found to cross-react with the LMP-derived peptides. Cross-reacting proteins were also identified in normal mouse tissues. The specificity of the cross-reacting antibodies was confirmed by inhibition experiments with the corresponding peptide. Furthermore, antibodies eluted from individual bands were shown to bind to the same band when reacted with new blots of the same extracts. Our data suggest that normal cells contain a family of highly conserved proteins cross-reacting with the LMP molecule. If, indeed, these proteins share common functions, their study may lead the way to unraveling the function of LMP.

Molecular cloning of a cDNA encoding the human Sm-D autoantigen

Antibodies to the Sm-D polypeptide antigen are closely associated with the rheumatic disease systemic lupus erythematosus. Sm-D exists in the cell as one of the core proteins of the small nuclear ribonucleoprotein complexes implicated in RNA processing. We have isolated a cDNA clone, D45-2, coding for the Sm-D human nuclear antigen by screening a human B-lymphocyte cDNA library with synthetic oligonucleotide probes. The 1633-base-pair clone contains an open reading frame (ORF) 357 nucleotides long, capable of encoding a 13,282-dalton polypeptide. The Sm-D coding region is initiated at an AUG codon downstream from a sequence with excellent match to the consensus for the eukaryotic ribosome-binding site. The Sm-D ORF is preceded by a 150-nucleotide-long untranslated leader and followed by a 1126-nucleotide-long untranslated region containing four putative poly(A) signals. The predicted amino acid sequence reveals a (Gly-Arg)9 repeated motif at the C terminus, which may constitute one of the Sm-D immunoreactive determinants. Moreover, this C terminus shows interesting features: (i) a good homology to protamines as expected for a nucleic acid binding protein and (ii) a striking similarity to a region in the Epstein-Barr nuclear antigen.

Three Epstein-Barr virus (EBV)-determined nuclear antigens induced by the BamHI E region of EBV DNA

In our previous study (Takada et al., 1986a), we showed that the BamHI E fragment of Epstein-Barr virus (EBV) DNA induces a nuclear antigen that is detected by human antisera against EBV-determined nuclear antigen (EBNA), when transfected into baby hamster kidney (BHK) cells. The present study shows that the sub-fragment containing the central open reading frame BERF2b of the BamHI E fragment (Baer et al., 1984) is responsible for nuclear antigen induction. In addition, 2 fragments corresponding to 2 other open reading frames of the BamHI E, BERFI and BERF4 also induce nuclear antigens upon transfection into BHK cells. These 3 antigens, designated RF2b, RFI and RF4 antigens, were serologically classified as EBNA and antigenically distinct. In immunoblotting analysis of latently EBV-infected BJ-B95-8 cells, 3 high-molecular-weight polypeptides (136, 142 and 147 kDa) were identified by anti-EBNA sera. Immunoblotting analysis of transfected BHK cells indicated that the RF2b antigen is 145 kDa in its native form and antigenically related to the 147-kDa protein of BJ-B95-8 cells. Although RFI and RF4 antigens were not detected by immunoblotting, reactivities of sera with RFI and RF4 antigens in the immunofluorescence test were correlated with those of sera with the 136- and 142-kDa polypeptides of BJ-B95-8 cells, respectively. The results suggest that 3 high-molecular-weight proteins of latently EBV-infected cells are encoded by 3 open reading frames of the BamHI E DNA fragment.

The analysis of EBV proteins which are antigenic in vivo

We have used small random EBV B95-8 DNA fragments to generate a large genomic bank in a plasmid expression vector. This bank was screened with a pool of sera from individuals with IM thus allowing any EBV antigen which evoked an immune response in man to be identified. The characterization of four immunopositive clones obtained in this way is presented in this study. Three of these clones express viral ORF DNA sequences which are parts of larger ORFs in the BamH1 N(het), V and X regions of the B95-8 viral genome. cDNA cloning has been used to confirm that the cloned sequences from BamH1 N and V are expressed in cell culture and to identify the transcription units involved. The fourth clone expresses an ORF sequence located in the viral BamH1 F fragment in a region not previously recognized as having protein coding potential. The experimental design used here must reflect the situation in vivo and consequently these sequences must be expressed and be antigenic during IM.

BamHI E region of the Epstein-Barr virus genome encodes three transformation-associated nuclear proteins

Recombinant vectors carrying DNA fragments from the BamHI E region of the B95-8 Epstein-Barr virus (EBV) genome were transfected into COS-1 cells, and the transient expression of EBV-encoded nuclear antigens (EBNAs) was analyzed by using polyvalent human antisera and rabbit antibodies to synthetic peptides. Vector DNA containing two rightward open reading frames in the BamHI E fragment, BERF2a and BERF2b, induced the expression of a nuclear antigen identical serologically and with respect to size to the larger of the two polypeptides previously designated as EBNA4 in B95-8 cells. An antigen corresponding to the smaller polypeptide was induced in cells transfected with constructs that contained two neighboring reading frames, BERF3 and BERF4. This antigen also reacted with a rabbit antiserum to the synthetic peptide 203, deduced from BERF4. Thus, the findings show that the two components of the EBNA4 doublet in B95-8 cells are encoded by separate genes. The antigen encoded by BERF2a and/or BERF2b has been designated as EBNA4 and the antigen encoded by BERF3 and/or BERF4 has been designated as EBNA6. Polyvalent human antisera detected EBNA4 and EBNA6 in 9 of 11 lymphoid cell lines carrying independent EBV isolates. In the remaining two lines, either EBNA4 or EBNA6 was not detectable.

A promoter for the highly spliced EBNA family of RNAs of Epstein-Barr virus

A transcription start for the highly spliced EBNA group of RNAs in B95-8 cells has been identified in the short unique region of the virus genome. This promoter is used in many (but not all) human cell lines carrying Epstein-Barr virus, including a tightly latent human lymphoblastoid cell line. Another promoter for the EBNA RNAs was described previously in the internal repeat region of the virus genome. The existence of these alternative promoters may be important for differential control of EBNA gene expression.

Cellular and humoral immune responses to synthetic peptides deduced from the amino-acid sequences of Epstein-Barr virus-encoded proteins in EBV-transformed cells

Ten synthetic peptides containing 18-22 residues deduced from the amino-acid sequences of the EBV-encoded latent-infection-associated membrane protein (LMP) and the 2 principal nuclear antigens, EBNA-1 and EBNA-2, were tested for their ability to induce lymphokine release from sensitized T-cells of EBV-seropositive donors, as measured by the leukocyte migration inhibition assay (LMI). Only one of the 10 free peptides induced EBV-specific LMI. After Sepharose-coupling, 4 additional peptides were regularly active. In parallel, the sera of the same and other donors were screened for synthetic peptide-binding antibodies, as measured by an ELISA assay. Antibodies to 9 of the 10 peptides were detected in 25-80% of EBV-antibody-positive, but not in EBV-antibody-negative sera. A comparison of the two responses indicates that the humoral immune system tends to react with more epitopes on a given protein than the cellular immune system. Furthermore, the antibody reactivity pattern to different epitopes is more variable from individual to individual than the T-cell response. Also, the epitopes detected by antibodies and sensitized T-cells are often not identical.

Site-directed serology with synthetic peptides representing the large glycoprotein G of respiratory syncytial virus

A set of 23 nested 15-amino-acid-long peptides with overlaps of 5 amino acids, representing the complete extramembranous part of the large glycoprotein G of respiratory syncytial (RS) virus, was analyzed in ELISA against different sera containing virus-specific antibodies. Seven of the peptides reacted with rabbit hyperimmune sera against purified virions. In contrast, only one of these seven peptides reacted with murine monoclonal antibodies specific for G. In connection with RS virus infections in humans, increase of antibody titers against three peptides was found in about one-third of the cases. These three peptides were included among those identified by both murine and rabbit antibodies. The present findings may open possibilities for site-directed clinical serology in the case of RS virus infections.

Conversion of the lymphoma line "BJAB" by Epstein-Barr virus into phenotypically altered sublines is accompanied by increased c-myc mRNA levels

The steady-state level of c-myc proto-oncogene mRNA was investigated in the EBV-negative human B-lymphoma line BJAB and 2 sublines that have been converted by EBV into stable EBV-genome-carrying and EBNA-positive status. The EBV-converted sublines expressed c-myc at a 2- to 6-fold higher level than the original BJAB during exponential growth. The EBV-positive BJAB lines are known to differ from the parent line in several phenotypic characteristics, including increased agarose clonability, lower serum requirement and, in one case, increased tumorigenicity in nude mice. The pattern of increased c-myc expression accompanying EBV conversion was not observed in the myc/Ig translocation-carrying Burkitt lymphoma line RAMOS or in 2 of its EBV-converted sublines.

EBV-transformed lymphoblastoid cell lines down-regulate EBNA in parallel with secretory differentiation

Four monoclonal and one polyclonal lymphoblastoid cell line (LCL) were studied with regard to cytoplasmic immunoglobulin (cIg) expression, presence of the Epstein-Barr virus (EBV)-determined nuclear antigen (EBNA) and DNA synthesis. Each line was found to consist of two subpopulations, with only minimal overlap. Proliferating, EBNA-positive, cIg-negative cells formed the majority. The minority were EBNA-negative, contained abundant cIg and were largely non-proliferating. This suggests the continuous occurrence of a maturation process within each LCL. The concomitant down-regulation of EBNA raises the interesting question whether continued synthesis of the nuclear antigen is incompatible with differentiation for epigenetic reasons, or, alternatively, whether differentiation takes place when the viral genomes are suppressed or lost.

Antibody responses to Epstein-Barr virus-determined nuclear antigen (EBNA)-1 and EBNA-2 in acute and chronic Epstein-Barr virus infection

Five distinct Epstein-Barr virus (EBV)-determined nuclear antigens (EBNA-1 to EBNA-5) were recently identified. Antibody responses to these antigens could conceivably differ, and thus prove of serodiagnostic value, in EBV-associated disease processes. As a first step, murine or human cell lines transfected with appropriate EBV DNA fragments and stably expressing either EBNA-1 or EBNA-2 were used to determine the frequency and time of emergence of antibodies to these two antigens in the course of acute and chronic infectious mononucleosis (IM) and to assess their titers in so-called chronic active EBV infections. Following IM, antibodies to EBNA-2 arose first and, after reaching peak titers, declined again in time to lower persistent or even nondetectable levels. Antibodies to EBNA-1 emerged several weeks or months after anti-EBNA-2 and gradually attained the titers at which they persisted indefinitely. The ratios between the anti-EBNA-1 and anti-EBNA-2 titers therefore were generally well below 1.0 during the first 6-12 months after IM and turned to well above 1.0 during the second year. In clear cases of chronic IM, the inversion of this ratio was delayed or prevented. In the less well-defined chronic EBV infections, low ratios were observed in only some of the patients. Because many of these illnesses were not ushered in by a proven IM and often showed EBV-specific antibody profiles within the normally expected range, a causal role of the virus in these cases remains doubtful.

Lymphoblastoid cell lines and Burkitt-lymphoma-derived cell lines differ in the expression of a second Epstein-Barr virus encoded nuclear antigen

Twenty-seven Epstein-Barr virus (EBV)-transformed lymphoblastoid cell lines and 27 EBV-carrying Burkitt-lymphoma-derived lines were analyzed for expression of the second EBV-encoded nuclear antigen (EBNA-2) by immunoblotting and anticomplement immunofluorescence with EBNA-2-specific sera. While all lymphoblastoid cell lines expressed EBNA-2, only 10 of the 27 BL lines were EBNA-2-positive. Comparison of the EBNA-2 coding BamHI W-, Y- and H-fragments of EBV-DNA in the different cell lines by restriction enzyme analysis suggests that EBNA-2 negativity is due either to sequence diversity or to a deletion in the BamHI WYH region.

Epstein-Barr virus mRNAs produced by alternative splicing

The structure of Epstein-Barr virus mRNAs transcribed in B95-8 cells has been studied by cDNA cloning and sequencing. We present here the analysis of four cDNAs. The corresponding mRNAs are probably transcribed from a single promoter located in the US region. They are produced by alternative splicing of exons transcribed from the US, IR and UL regions. The exons are spread over 100 kbp. The exons from the IR region constitute a unit which is repeated several times. The cDNAs share the exons from the US and IR regions. Some of the cDNAs also share some of the exons from the UL region. Each cDNA contains a long open reading frame or the 5' end of a long open reading frame which ends several hundred nucleotides downstream on the viral genome. The 5' untranslated regions are unusually long. Three mRNA species differing in their 5' untranslated regions may encode for the nuclear antigen EBNA-1. The other mRNAs encode for polypeptides which may not have any common region.

An Epstein-Barr virus (EBV)-determined nuclear antigen (EBNA5) partly encoded by the transformation-associated Bam WYH region of EBV DNA: preferential expression in lymphoblastoid cell lines

Four peptides were synthesized on the basis of amino acid sequences deduced from a highly spliced transcript encoded by the Bam W, Y, and H fragments of the Epstein-Barr virus (EBV) genome [Bodescot, M., Chambraud, J. B., Farrell, P. J. & Perricaudet, M. (1984) EMBO J. 3, 1913-1917]. Rabbit antisera against three of the four peptides identified a nuclear polypeptide that varied between 22 and 70 kDa in molecular size. Four of 20 EBV-positive human sera contained antibodies against this polypeptide. Since this is the fifth EBV-determined nuclear antigen (EBNA) discovered in growth-transformed cells, it is designated EBNA5. The antigen was detected in virus nonproducer lines (less than 0.01% EBV early antigen expression) and is thus not dependent on the viral cycle. It was differentially expressed depending on the origin of the lines. All 10 lymphoblastoid cell lines tested expressed EBNA5, but it could not be detected in 10 of 11 EBV-carrying Burkitt lymphoma lines. Infection of tonsillar lymphocytes with the B95-8 strain of EBV induced six EBNA5-specific polypeptides that varied between 41 and 70 kDa in molecular size with regular increments of 6 kDa. This may be due to the fact that the EBNA5 coding sequence includes the Bam W internal repeat. Parallel infection of the EBV-negative Burkitt lymphoma line Ramos with the same viral substrain did not induce detectable levels of EBNA5, nor was this antigen present in permanently EBV-converted Ramos sublines. These findings imply that the expression of the viral genome varies among B cells having different phenotypes.

Deletion mutants that affect expression of Epstein-Barr virus nuclear antigen in COS-1 cells after gene transfer with simian virus 40 vectors containing portions of the BamHI K fragment

We have identified sequences that affect the efficient expression of Epstein-Barr virus nuclear antigen (EBNA 1) when the structural portion of its gene, found within the 2.9-kilobase-pair BamHI/HindIII fragment called Ilf, is expressed from a simian virus 40 vector. A set of nested deletions at the BamHI end of the fragment was constructed by using BAL 31 digestion, the addition of linkers, and ligation into pSVOd. The mutants were tested for their ability to express antigen in COS-1 monkey cells by using indirect immunofluorescence and immunoblotting. Deletion endpoints were determined by DNA sequencing of the 5' ends of the mutants. The deletion mutants could be subclassified into four groups based on their ability to express EBNA polypeptide. Mutants that retain more than 106 base pairs upstream from the start of the open reading frame in Ilf exhibit antigen expression indistinguishable from that of wild type. Mutants that invade the structural gene by 1,115 or more bases destroy antigen expression. Mutants that alter the splice acceptor site or invade the open reading frame by a short distance make antigen at a markedly lower frequency. There are three mutants, whose deletions map at -78, -70, and -44 base pairs upstream of the open reading frame, that make reduced levels of EBNA. Since these three mutants differ in the extent to which EBNA expression is impaired, the data suggest that there are several critical regions upstream of the open reading frame that regulate EBNA expression in COS-1 cells. It is not known whether these regulatory sequences, which would be located in an intron in the intact genome, play any role in the expression of EBNA in infected lymphocytes.

An Epstein-Barr virus transcription unit is at least 84 kilobases long

We have studied the structure of the Epstein-Barr virus mRNAs expressed in B95-8, a productively-infected Marmoset cell line established from in vitro-infected B-lymphocytes. We constructed a cDNA library from the cytoplasmic polyadenylated RNAs of B95-8 in the lambda gt10 bacteriophage. We present here the analysis of a 3.5 kbp cDNA containing exons transcribed from the US, IR and UL regions of the viral genome. The corresponding transcription unit is at least 84 kbp long. Two exons are transcribed from the US region, five from the IR region and two from the UL region. The exons from the IR region consist of two tandem repeats of a unit containing two exons, 66 and 132 nucleotides, and of a third copy of the 66 nucleotide exon. The exons from the UL region contain an open reading frame coding for a 944 amino acid polypeptide. The C-terminal end of this polypeptide harbors three types of repeated sequences. The corresponding mRNA is the second described of a family of mRNAs produced by alternative splicing of exons transcribed from the US, IR and UL regions.

Four virally determined nuclear antigens are expressed in Epstein-Barr virus-transformed cells

The expression of Epstein-Barr virus (EBV)-determined antigens associated with growth-transformation of B cells was studied by immunoblotting with human sera from healthy donors. Four antigens were detected in EBV-carrying cell lines and in B lymphocytes early after infection with the transforming B95-8 substrain of virus. They were not found in uninfected cells, nor could they be demonstrated with sera lacking antibodies to EBV antigens. All four antigens were nuclear. Each of them varied in size in the different cell lines. The two antigens with the lowest molecular weight were identified as EBV-determined nuclear antigens (EBNAs) 1 and 2. The two high molecular weight antigens (140-160 kDa and 150-180 kDa, respectively) were detected with 6 of 16 EBV antibody-positive sera. These proteins appeared to be antigenically unrelated to each other and to EBNAs 1 and 2 and were designated EBNAs 3 and 4. Like EBNAs 1 and 2, they bound to double- and single-stranded DNA in vitro.

The Epstein-Barr virus determined nuclear antigen is composed of at least three different antigens

The EBV-determined nuclear antigen, EBNA, is the only known viral product to be regularly detected in all EBV-transformed cells. The anticomplement immunofluorescence (ACIF) staining detects an EBV-specific nuclear reaction that has recently been shown to be due to at least 2 different proteins, EBNA-1 and EBNA-2, encoded by different parts of the viral genome. We now report the existence of a third antigen of the EBNA complex, designated as EBNA-3. Serum from a patient with chronic infectious mononucleosis contained no detectable antibodies to EBNA-I and had only a low EBNA-2 antibody level. Nevertheless, it gave an EBV-specific nuclear reaction of normal intensity and stained EBNA-2-positive and EBNA-2-negative EBV-carrying lines equally well. Immunoblotting with the same serum identified a new EBV-specific nuclear protein of 143-157 kDa.

A third viral nuclear protein in lymphoblasts immortalized by Epstein-Barr virus

Most sera from patients with rheumatoid arthritis as well as some sera from normal Epstein-Barr virus (EBV)-infected people detect a 140-kDa protein on immunoblots of EBV-infected lymphoblasts. The 140-kDa protein is a nuclear protein characteristic of latent EBV infection. Sera reactive with this protein identify a distinctive globular nuclear antigen. Although the 140-kDa protein is encoded by EBV, it is not encoded by genes that encode the two previously described EBV nuclear antigens (EBNA) or the latent-infection membrane protein. The 140-kDa protein is therefore designated EBNA3. The EBV genes, including the gene encoding EBNA3, that are characteristically expressed in latent infection are likely to play a role in the maintenance of persistent latent viral infection or in the cell proliferation caused by virus infection.

Carboxyl-terminal domain of the Epstein-Barr virus nuclear antigen is highly immunogenic in man

The carboxyl-terminal one-third of the Epstein-Barr virus nuclear antigen (EBNA-1) encoded by the BamHI restriction fragment K was synthesized in Escherichia coli by use of a high-expression plasmid. The resultant 28-kDa EBNA fusion polypeptide, comprising 5-10% of the total soluble bacterial protein, was purified to apparent homogeneity by phosphocellulose and hydroxylapatite column chromatography. Both rabbit monospecific antibodies and mouse monoclonal antibodies against 28-kDa EBNA gave nuclear immunofluorescence staining on Epstein-Barr virus (EBV)-infected lymphoblastoid cell lines and recognized the appropriate intact EBNA polypeptide bands on immunoblots. An ELISA with the purified 28-kDa EBNA as antigen was used to quantitate anti-EBNA antibody in human serum samples. The ELISA method was approximately 100-fold more sensitive than the classical anticomplement immunofluorescence assay. Anti-EBNA antibody was detected in sera from 100% of normal individuals who were seropositive for the viral capsid antigen, and low anti-EBNA titers were detected in serum from most patients with acute infectious mononucleosis. The assay gave the expected pattern of titers in sera from patients with rheumatoid arthritis, Burkitt lymphoma, or nasopharyngeal carcinoma, thus confirming the validity of this purified reagent for assessing EBNA antibody status. Approximately 10% of normal individuals and rheumatoid arthritis patients had anti-EBNA titers as high as those seen in nasopharyngeal carcinoma patients. In these high-titer individuals, greater than 1% of the total IgG are antibodies that recognize 28-kDa EBNA, which indicates that the carboxyl-terminal domain of EBNA is highly immunogenic.

Antibodies against synthetic peptides react with the second Epstein-Barr virus-associated nuclear antigen

Five peptides were synthesized on the basis of amino acid sequences predicted from the transformation-associated BamHI WYH region of the genome of the Epstein-Barr virus (EBV). Antisera to two peptides deduced from a 1.6-kb open reading frame in the BamHI H fragment identified an 87 000-dalton nuclear polypeptide that was present in EBV-carrying cell lines that expressed the second EBV-determined nuclear antigen (EBNA-2). This polypeptide was not detected in cell lines that carried EBV variants with a deleted BamHI WYH region or in EBV-negative cell lines. Three peptides deduced from the 1.6-kb open reading frame reacted with human EBNA-positive sera, but not with EBNA-negative sera. Following affinity purification with the peptides, two of the corresponding human antibodies also reacted with the 87 000-dalton polypeptide.

Repeat arrays in cellular DNA related to the Epstein-Barr virus IR3 repeat

We isolated clones and determined the sequence of portions of mouse and human cellular DNA which cross-hybridize strongly with the IR3 repetitive region of Epstein-Barr virus. The sequences were found to be tandem arrays of a simple sequence based on the triplet GGA, very similar to the IR3 repeat. The cellular repeats have distinct differences from the viral repeat region, however, and their sequences do not appear capable of being translated into a purely glycine-plus-alanine protein domain like the portion of the Epstein-Barr nuclear antigen coded by IR3. Although the relationship between IR3 and the cellular repeats is left unclear, the cellular repeats have many interesting features. The tandem arrays are about 1 to several kilobases long, much shorter than satellite tandem repeats and larger than other interspersed, tandem repeats. Each of the repeats is a distinct variation, perhaps diverged from a common sequence, (GGA)n. This family is present in the genomes of all species tested and appears to be a ubiquitous feature of all higher eucaryotic genomes.

Expression of a second Epstein-Barr virus-determined nuclear antigen in mouse cells after gene transfer with a cloned fragment of the viral genome

Large Epstein-Barr virus (EBV) DNA restriction fragments corresponding to regions transcribed in transformed, proliferating cells were cloned in a cosmid derivative of the dominant-acting selection vector pSV2-gpt. Recombinant vectors carrying the EcoRI A fragment of EBV DNA were modified in the region corresponding to the deletion of the virion DNA in the non-transforming viral substrain P3HR-1, to create a series of recombinants lacking parts of this region. The recombinant vectors were introduced into 3T3 mouse fibroblasts under selective conditions, and resistant clones shown to contain EBV DNA sequences were analyzed for the expression of EBV-related antigens detectable by direct, indirect, and anticomplement immunofluorescence techniques. Cells that contained the BamHI K fragment expressed the EBV-determined nuclear antigen (EBNA) as expected. Cells transfected with recombinant vectors containing the BamHI W, Y, and H fragment part of the EcoRI A fragment also express a nuclear antigen detectable with certain anti-EBNA-positive human sera in anticomplement immunofluorescence tests. The BamHI WYH-induced EBNA polypeptide is similar in size to the EBNA2 polypeptide in Raji cells, as shown by gel electrophoresis and immunoblotting. The antigen is not detected in cells transfected with EcoRI A-derived vectors in which the BamHI H fragment has been deleted or in cells transformed with vectors carrying the BamHI H fragment alone. Direct and indirect immunofluorescence did not reveal the presence of antigens associated with productive infection in any of the EBV DNA-transfected fibroblast clones.

Purification of Epstein-Barr virus DNA polymerase from P3HR-1 cells

The Epstein-Barr virus DNA polymerase was purified from extracts of P3HR-1 cells treated with n-butyrate for induction of the viral cycle. Sequential chromatography on DNA cellulose, phosphocellulose, and blue Sepharose yielded an enzyme preparation purified more than 1,300-fold. The purified enzyme was distinct from cellular enzymes but resembled the viral DNA polymerase in cells infected with herpes simplex virus type 1 or 2. The active enzyme had an apparent molecular weight of 185,000 as estimated by gel filtration on Sephacryl S-300. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed a major polypeptide corresponding to a molecular weight of ca. 110,000. This polypeptide correlated with the catalytic function of the purified enzyme, whereas the other, less abundant polypeptides did not. By immunoblotting, the 110,000-molecular-weight polypeptide could be identified as a viral polypeptide. It could not be determined whether the native enzyme was composed of more than one polypeptide.

Latent and viral replicative transcription in vivo from the BamHI K fragment of Epstein-Barr virus DNA

We mapped one latent and two replicative messages transcribed in vivo from the BamHI K fragment of the Epstein-Barr virus genome. The exon encoding Epstein-Barr nuclear antigen (EBNA), a major latent product, is 2,028 bases; the 3' end of this exon occurs 30 bases after the polyadenylation signal AATAAA, and the 5' end occurs within a splice acceptor site. The open reading frame which encodes the EBNA peptide is completely contained within this coding exon. The exon was faithfully transcribed after transfection of cloned BamHI-K into either COS-1 or TK- mouse L cells. In lymphocytes the abundance of the EBNA message is increased after cycloheximide treatment. The two viral replicative genes completely contained in BamHI-K were not transcribed in line X50-7, in which the genome is tightly latent. In contrast to the EBNA message, these mRNAs of 1.3 and 2.1 kilobases are inducible with phorbol ester and are unspliced. Their promoter regions are similar to those of each other and to replicative promoters mapped in other regions of the Epstein-Barr virus genome (P. J. Farrell, A. Bankier, C. Seguin, P. Deininger, and B. G. Barrell, EMBO J. 2:1331-1338, 1983). An unusual feature of these replicative genes is that the smaller mRNA begins within a long open reading frame of the larger mRNA. The identification of the structure of latent and replicative genes within one DNA fragment will facilitate analysis of regulation of expression for the two life cycles of the virus.

Characterization of a second Epstein-Barr virus-determined nuclear antigen associated with the BamHI WYH region of EBV DNA

The Epstein-Barr virus-determined nuclear antigen (EBNA) is the only known virally-determined component that is regularly associated with EBV-transformed cells. A main component of EBNA, herein designated EBNA-1, has been conclusively localized to the BamHI K fragment of the viral genome. EBNA-1 is present in all EBV-carrying cell lines so far studied. Our current study deals with a second component. We have found that the EBNA reaction detected by anti-complement immunofluorescence (ACIF) in Burkitt lymphoma lines Daudi, Jijoye, and P3HR-1 could be completely removed by preabsorption of sera with any one of these 3 lines, when tested against any other of them. The same absorbed sera still gave a brilliant nuclear staining against other EBV-carrying lines, e.g. Raji or B95-8. The 3 lines in the first category carry EBV genomes that have deletions in the BamHI WYH region of the EBV genome. This region is intact in the second group of lines. This result is interpreted as showing the existence of 2 different ACIF-stainable EBV-determined nuclear antigens, one of which is associated with the BamHI WYH region. We designate this antigen as EBNA-2. We found that the two different EBNAs are different with regard to their association with metaphase chromosomes. In lines positive for both EBNA subtypes, metaphase chromosomes gave brilliant EBNA-1 staining, but could not be stained for EBNA-2, indicating differences in chromatin association of the two EBNAs. An 86 kd polypeptide was identified by immunoblotting of DNA-binding proteins from EBV-transformed lymphoid cell lines. EBV-specificity of the polypeptide was demonstrated by the presence of antibodies against this polypeptide in antisera from a population of EBV-seropositive donors, but not from seronegative donors, by the presence of the polypeptide itself in EBV-carrying but not in EBV-negative cell lines and by the appearance of antibodies against this polypeptide during the course of infectious mononucleosis (IM). The polypeptide was absent from the EBV-carrying P3HR-1, Daudi and Jijoye cell lines, which suggested that it may be encoded by the BamHI WYH region that is deleted from the viral substrains carried by these lines.

Repeat arrays in cellular DNA related to the Epstein-Barr virus IR3 repeat

We isolated clones and determined the sequence of portions of mouse and human cellular DNA which cross-hybridize strongly with the IR3 repetitive region of Epstein-Barr virus. The sequences were found to be tandem arrays of a simple sequence based on the triplet GGA, very similar to the IR3 repeat. The cellular repeats have distinct differences from the viral repeat region, however, and their sequences do not appear capable of being translated into a purely glycine-plus-alanine protein domain like the portion of the Epstein-Barr nuclear antigen coded by IR3. Although the relationship between IR3 and the cellular repeats is left unclear, the cellular repeats have many interesting features. The tandem arrays are about 1 to several kilobases long, much shorter than satellite tandem repeats and larger than other interspersed, tandem repeats. Each of the repeats is a distinct variation, perhaps diverged from a common sequence, (GGA)n. This family is present in the genomes of all species tested and appears to be a ubiquitous feature of all higher eucaryotic genomes.