Gene regulation by sense–antisense overlap of polyadenylation signals

(A) Mutant viruses with altered late polyadenylation signals. (Boxes) AAUAAA elements; (circles) translation stop codons for viral proteins. Mutant YZ-3 was described previously and grows like wild type, with a normal early-to-late switch (Gu et al. 2006). Mutant Space-75 was made by replacing the BglII-XhoI segment of YZ-3 with a fragment containing the bovine growth hormone (BGH) or human β-globin poly(A) signals, separated by 75 bp and with a unique NotI site for the insertion of additional spacer sequences, indicated at the bottom.