Effect of RNA structural mutations on temperature-sensitivity. (A)
Paralytic editing sites 1 to 3 (red), within an exon (blue), are encompassed within a complex tertiary structure involving three intronic (black) sequences: the editing site complementary sequence (ECS), the donor site complementary sequence (DCS) and a hairpin (HP), the loop of which forms a tertiary psueoknot with a docking site 3’ to the ECS. The DCS region is boxed for comparison with the knock in structural mutations. (B) In the ‘DCS delete’ mutation, the DCS region of the intron is excised (gray dotted line), resulting in a loss of secondary structure. (C) In the ‘DCS zip’ mutation, the DCS secondary structure is extended by nine base pairs, due to the insertion of seven nucleotides (green) within the intronic sequence. (D) Because these mutations overall decrease (DCS delete) or increase (DCS zip) editing at all three sites , the slopes of the editing response curves, rather than the absolute editing, was compared to loxP. The DCS delete (light green) and DCS zip mutation (dark green) show a different temperature-sensitive response pattern than that of the loxP control (gray). P <0.0001: **, P <0.05: *.