FIG. 6.

(A) Schematic representation of subgenomic HPV-16 expression plasmids pBELM, pT9, pT10, and pOPSDM. Numbers indicate the nucleotide positions of 5′ splice sites (filled circles) and 3′ splice sites (empty circles) or the positions of pAE and pAL or mark the borders of deletions. The exact sequences of wild-type (wt) and mutant SD3632 are indicated. Major potential mRNAs produced by these plasmids are indicated below. The L1 probe used for Northern blotting is indicated. Mut, a mutant L1 gene in which splicing silencers have been inactivated (11, 61). (B, C, and D) Northern blots of cytoplasmic RNA extracted from HeLa cells transfected with pBELM, pT9, pT10, or pOPSDM in the absence or presence of a PTB-expressing plasmid. Blots were probed with the L1 probe and a GAPDH probe. The position of the L1 mRNA is indicated. +, present; −, absent.