Rescue of transforming Epstein-Barr virus (EBV) from EBV-genome-positive epithelial hybrid cells transfected with subgenomic fragments of EBV DNA

Mapping of genes in BamHI fragment M of Epstein-Barr virus DNA that may determine the fate of viral infection

We used nuclease digestion to map RNA transcripts encoded in the BamHI M fragment of the Epstein-Barr virus (EBV) genome (strain B95-8). Of the five RNAs, three are rightwardly transcribed, have different cap sites but common 3' termini, and are unspliced. The two remaining RNAs are leftwardly transcribed and are 5' and 3' coterminal. One of these transcripts is spliced, resulting in the removal of a small intron from the 5' region of this RNA. We have previously published data which indicated that the BamHI M region is the first actively transcribed region of the viral genome during the replicative cycle, suggesting that one or more genes in this region is important in the initiation of EBV replication. We have now mapped two large EcoRI restriction fragments which span approximately 75% of the P3HR-1 defective genome and which contain DNA from the BamHI M region of the standard genome. The data indicate that only the coding and 5' flanking sequences for the leftwardly transcribed RNAs are intact within the defective genome. Fewer than 500 bases coding for the 3'-most regions of the rightwardly transcribed RNAs are intact, and it is unlikely that these encode functional native polypeptides. Therefore, it seems that transcriptional activation of the BamHI M-region genes is not mediated directly by the rearrangement of M genes in defective P3HR-1 EBV.

Activation of expression of latent Epstein-Barr herpesvirus after gene transfer with a small cloned subfragment of heterogeneous viral DNA

We previously found that a form of Epstein-Barr virus with rearranged DNA induces replication of latent Epstein-Barr virus. We now have found that one of three fragments of this rearranged DNA, when cloned in recombinant plasmids and used to transfect cells, can activate expression of several polypeptides from a latent viral genome. The 33-kDa protein that is the product of the active fragment is likely to be responsible for disruption of latency.

Expression of Epstein-Barr virus (EBV) DNA and cloned DNA fragments in human lymphocytes following Sendai virus envelope-mediated gene transfer

Purified EBV DNA and cloned DNA fragments were trapped in Sendai virus (SV) envelopes during envelope reconstitution. The DNA-loaded reconstituted envelopes (RSVE/DNA) served as gene-transfer vehicles using the capability of RSVE to fuse with normal and tumor cells. The efficiency of RSVE-mediated EBV DNA transfer into lymphoid tumor cells and fresh human lymphocytes was 5-10% of the enveloped 3H-labeled EcoRI fragment B of EBV DNA. Purified intracellular EBV (B95-8 strain) DNA induced EBV nuclear antigen (EBNA) in 0.2-1% of human lymphocytes, transiently stimulated cellular DNA synthesis, but did not fully transform cells. Cloned Sal I F1 fragment [approximately equal to 9 kilobase pairs (kbp)] and a smaller BamHI K (5.2 kbp) fragment from the same region of B95-8 EBV DNA induced EBNA in 2-4% of human lymphocytes but did not stimulate DNA synthesis nor transform cells. Cloned BamHI D1 fragment (approximately equal to 9 kbp) from AG-876 virus DNA, or a combination of cloned BamHI X and H fragments (approximately equal to 2 and 7 kbp, respectively) from the similar region of B95-8 virus DNA, significantly stimulated lymphocyte DNA synthesis, but EBNA could not be detected and transformation was not achieved. Early antigen and viral capsid antigen were not observed with any of the fragments tested. Our results suggest that the induction of EBNA and stimulation of lymphocyte proliferation are not controlled by the same region of EBV DNA.

Expression of a nuclear and a cytoplasmic Epstein-Barr virus early antigen after DNA transfer: cooperation of two distant parts of the genome for expression of the cytoplasmic antigen

Expression of Epstein-Barr virus (EBV) antigens was studied after transfection of cloned EBV DNA fragments into baby hamster kidney (BHK) cells. A set of seven widely overlapping clones covering the whole genome of the non-defective Epstein-Barr virus strain M-ABA was used for transfection. Transfer of the cosmid clones into BHK cells resulted in expression of two distinct antigens, as revealed by indirect immunofluorescence using human anti-EBV sera. Staining with human sera of different reactivity against EBV-associated antigens revealed that both types of antigens were related to the early antigen complex. The first type of antigen was detected only in the nuclei of BHK cells that had received DNA of a clone containing HindIII-G, -H, -E, -I2, -O, -I1, and -P. The second type of antigen was found in the cytoplasm of cells cotransfected with clones containing Sal-A and HindIII-I2, -O, -I1, -P, and -C, whereas transfection of both individual clones failed to induce the antigen. Further analysis with subclones identified HindIII-G (5 kilobases) and HindIII-I2 (3 kilobases) plus the rightmost 3 kilobases of Sal-A as the sequences responsible for expression of the nuclear and the cytoplasmic antigen, respectively. The fact that two distant regions of the viral genome are required for expression of a viral antigen provides evidence for intergenomic regulation that can be studied in vitro.