“Dual use” signals in protists. (A) Switching the poly(A) signal from AAUAAA to WGURAA extends the number of possible “dual use” signals from 5 (left panel) to 9 (right panel). Poly(A) signal sequence is colored green (AAUAAA) or blue (WGURAA), stop codon sequence is highlighted gray. (B) Stop codons of 8%–20% of protein-coding genes in Giardia overlap with poly(A) signals. Almost all overlapping poly(A) signals are WGURAA. In contrast, AAUAAA makes up the majority of overlapping poly(A) signals for N. gruberi. (C) Length comparison between 3′ UTRs with and without “dual use” signals for G. lamblia A and N. gruberi. 3′ UTRs containing these signals are significantly shorter. Median length is shown below the plot.
