The inclusion of PGRP-LCx and LCy isoforms is directed by competing RNA pairings. (A) The arrangement of cis intronic elements at the 3′ variable region. Symbols used are the same as those in Figure 1A. Shown above are the sequences of consensus intronic sequences for different species. The most identical nucleotides in the docking site
(RE) and selector sequences (CE1 and CE2) are shown in green and red, respectively. Sequences of the same color are highly
similar. For predicted intronic RNA pairings, see Supplemental Figure S1. Docking site (RE, marked 
) was reverse-complementary to downstream selector sequences (CE1 and CE2, marked 
) in a competitive mode. (B) Predicted mutually exclusive RNA pairings. Mutations introduced into dsRNA are indicated on the left or right mutated sequences (M1–M3). Green arrows depict activated inclusion of the alternative exon. (C) Overview of the minigene constructs of D. melanogaster used to assess the effects of RNA pairing on splicing. (D) Effects of competing RNA pairings were validated by disruptive single mutations (M1–M3) and compensatory double mutations
(M12, M13). (E) Quantitation of the data in D. Data are expressed as the percentage mean ± standard deviation (SD).
