<p>The splicing of the <i>RPL22B</i> intron was affected by the pre-mRNA context.</p>

The structure was modeled by RNAfold [<a href="plosone.org/article/info:doi/10.1371/journal.pone.0359197#pone.0359197.ref052" target="_blank">52</a>], visualized using Forna [<a href="plosone.org/article/info:doi/10.1371/journal.pone.0359197#pone.0359197.ref058" target="_blank">58</a>] and annotated according to [<a href="plosone.org/article/info:doi/10.1371/journal.pone.0359197#pone.0359197.ref011" target="_blank">11</a>]. ‘Clamp’ and ‘RNA internal loop’ (RIL) are labeled red and green, respectively.

In [<a href="plosone.org/article/info:doi/10.1371/journal.pone.0359197#pone.0359197.ref011" target="_blank">11</a>], ‘Clamp’ is referred to as ‘Lower distal stem.’ (C) Structure, but not the sequence of the ‘Clamp’ was important for splicing regulation. Deletion of the 3’strand of the ‘Clamp’ or weakening of its complementarity rendered intron splicing permissive regardless of Rpl22. On the contrary, maintaining complementarity while scrambling the sequence or flipping the stem arms retained the WT behavior.

(D) Nucleotides within the ‘RNA internal loop’ were dispensable for the regulation of <i>RPL22B</i>i splicing. In contradiction to previous findings [<a href="plosone.org/article/info:doi/10.1371/journal.pone.0359197#pone.0359197.ref011" target="_blank">11</a>], nucleotides within the ‘RNA internal loop’ (RIL) are dispensable for the regulation of <i>RPL22B</i>i splicing. CCCU to AAAC mutation in the 5’arm of the loop (‘5’RIL AAAC’), the UGAA to CAUU mutation in its 3’arm (‘3’RIL CAUU’), or the deletion of the loop or its arms did not lose regulation after the overexpression of the Rpl22 protein. ΔRIL indicates the deletion of both 5’arm CCCU and 3’arm UGAA nucleotides; Δ5’RIL and Δ3’RIL indicate the per partes deletions of CCCU and UGAA, respectively.</p>