| Author |
Nomura T, Kim JS, Iwata O, Yamada K, Atsuji K, Uehara-Yamaguchi Y, Yoshida T, Inoue K, Takahagi K, Sakurai T, Shinozaki K, Ito T, Suzuki K, Goda K, Mochida K.
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| Abstract |
Pre-mRNA splicing is essential for eukaryotic gene expression and is achieved through the accurate recognition of exon-intron boundaries. Although nonconventional introns, which do not follow the conventional GT-AG splicing rule, have been identified in several species, these introns are typically rare in any given genome. Here, we demonstrate the widespread occurrence of nonconventional introns (71.8% of all introns) in the Euglena agilis genome and identify consensus motifs at these nonconventional exon-intron boundaries. We assessed the splicing efficiency of nonconventional introns and variants with point mutations via genomic knock-in within the second exon of Glucan synthase-like 2 in Euglena gracilis and genetically defined the sequence signature (5'-N3CDG-/-CH'GN5-6|Rexon-3') required for their proper splicing. This signature is present in 61.2% of all nonconventional introns detected in the E. agilis genome. Accordingly, we present a noncanonical splicing code for Euglena introns, highlighting the global coexistence of dual splicing rules for conventional and nonconventional introns.
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