Figure 3.

Diagram showing the splice sites used by selected HPV16 mRNAs. (A) Diagram of a linearised HPV16 genome showing coloured open reading frames. Promoters are indicated with blue horizontal arrows and designated “P” followed by a number. LRE, late regulatory element. p(AE), early polyadenylation site. p(AL), late polyadenylation site. (B) Diagrams of selected early mRNAs showing the readthrough mRNA (top diagram) and four mRNAs utilising the splice acceptor at the 5′ end of the E4 open reading frame. (C) Diagrams of early mRNAs utilising one of two splice acceptors located in the E2 open reading frame. Although only shown for splice acceptor 2709, it is assumed that mRNAs using each E2 splice acceptor can include any of the E6E7 region splice isoforms. (D) Diagrams of the main HPV16 late mRNAs. SD, splice donor site. SA, splice acceptor site. A(n), poly(A) tail. Exons are indicated with horizontal cylinders. Introns are indicated with dotted black lines. Splice donor and acceptor sites are indicated with black triangles.