FIG. 1.

Exon organization of EBNA-LP gene transcripts. Transcription of the EBNA-LP gene initiates from either the W promoter (Wp) or the C promoter (Cp). The different noncoding (C1, C2, and W0) and coding (W1, W2, Y1, and Y2) exons are indicated. During early stages of infection, transcription initiates from available Wps residing in each internal repeated region 1 (IR1) repeat, which results in the production of multiple EBNA-LP protein isoforms. During later stages of infection or in established lymphoblastoid cell lines (LCLs), transcription from Cp is stimulated and there is a bias toward the origin of replication (OriP)-proximal Wp. The level of Cp- versus Wp-initiated transcription varies depending on several circumstances. The viral latent OriP, the polyadenylation site (pA) for EBNA-LP/EBNA2 transcripts, and the locations of other EBNA genes and LMP are shown.