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. 2023 Oct 3;12:e91997. doi: 10.7554/eLife.91997

Figure 5. Inter-species association mapping links SNRNP27K Methionine 141–5’SS sequence preference.

(A) Stacked histogram and traitgram showing the distribution of 5’SS +4 A to U ratio phenotypes for species which retain or lack a SNRNP27K ortholog. Ancestral loss events shown on the traitgram are estimated using Dollo parsimony. (B) Boxplots showing the distribution of 5’SS +4 A to U ratio phenotypes for species retaining or lacking a SNRNP27K ortholog, whilst also controlling for the presence or absence of a METTL16 ortholog. (C) Stem plot showing the association of individual conserved positions in the C-terminus of SNRNP27K with the 5’SS +4 A to U ratio phenotype in 158 species retaining a SNRNP27K ortholog. The most strongly associated position is Met141, which is in extreme proximity to the ACAGA box in the pre-B complex. (D) Cryo-EM snapshot of the C-terminus of SNRNP27K in the pre-B complex, in close proximity to the region occupied by the flexible ACAGA box of the U6 snRNA. The surface of PRP8 is shown in grey. (E) Overlayed Cryo-EM snapshots showing the position of SNRNP27K in the pre-B complex, relative to the position of the ordered U6/5’SS helix in the B complex. Positioning of the components labelled with asterisks was determined relative to the position of pre-B complex PRP8 by the superimposition of the PRP8 structures from the pre-B and B complexes.

Figure 5.

Figure 5—figure supplement 1. Sequence analysis of the SNRNP27K C-terminal domain.

Figure 5—figure supplement 1.

(A) Sequence logo showing the alignment of the SNRNP27K orthologs from 158 species to the SNRNP27K C-terminal domain pHMM model. Position 141 (marked with an asterisk) is most commonly occupied by a methionine residue but is replaced in some species with a valine or isoleucine. (B) Boxplots showing the distribution of 5’SS +4 A to U ratio phenotypes for species retaining a SNRNP27K ortholog with a methionine in the pHMM alignment position corresponding to human Met141, compared to those with a different residue at this position (X141), and those that lack a SNRNP27K ortholog entirely.