Construction and use of cDNA clones for the mapping and identification of Epstein-Barr virus early P3HR-1 mRNAs

cDNA clones, specific for early Epstein-Barr virus (EBV) RNAs, were constructed from total cytoplasmic RNA of P3HR-1 TK- cells. From 10,000 cDNA clones screened, 22 virus-specific cDNA clones were selected by hybridization with a total EBV DNA. These clones were then precisely mapped on the EBV genome and the corresponding mRNAs were identified by Northern blot hybridizations. Most of them are clearly related to some of the open reading frames described by Baer et al. (Nature [London] 310:207-211, 1984). They represent at least 18 different genes active during the early viral cycle. The transcriptional activity of the virus during the early stage was also studied by dot blot hybridization of total early cDNA probe to EBV genomic fragments. Three main regions showed very strong hybridization with the cDNA probe: BamHI a, M, and L fragments, BamHI K, B, and G fragments, and BamHI B1 fragment (deleted in strain B95-8) and the adjacent right end of the DNA molecule. Seventeen of the cDNA clones were localized in these highly transcribed regions. The five others were dispersed all along the EBV genome.