Figure 1 - Logo analysis of 50 nt upstream and downstream of insertion sites of 43 different spliceosomal rRNA introns. The information content of the 2 Gs of the intron proto-splice site is shown as is a line at p = 0.05 (95% quantile) that is based on simulations using random sequence data. This exon region contains a total of 6.91 bits of information.

Figure 2 - The distribution of SSU and LSU rRNA spliceosomal introns relative to the G-frequency in these genes. The raw G-frequencies are shown in the green circles, the smoothed loess curves for 50 nt and 100 nt smoothing windows are shown with the blue lines, and the positions of introns are shown with the vertical red lines.

Figure 3 - Distribution of Euascomycetes spliceosomal introns on a conservation diagram of fungal SSU rRNA overlaid on a secondary structure model of the Saccharomyces cerevisiae SSU rRNA. Spliceosomal introns are shown in large text with arrows denoting their positions. Positions with nucleotides in more than 95% of the 1042 sequences that were studied are shown as following: upper case, conserved at >= 95%, lower case, conserved at 90-94%, filled circle, conserved at 80-89%, and open circle, conserved at < 80%. Other regions are denoted as arcs. The numbers at the arcs show the upper and lower number of nucleotides that are found in these variable regions. The boxed regions are G-rich sequences upstream of intron insertion sites. Boxed filled circles indicate that the most frequent nucleotide at this site was a G in our alignment of 1434 fungal rRNAs that included both intron-containing and intron-less taxa.

Figure 4 - Analysis of rRNA intron distribution. A. The positions of introns mapped on the homologous sites in the primary structure of E. coli SSU and LSU rRNA. Group I and group II (underlined) introns are shown above the lines, whereas spliceosomal and archaeal (underlined) introns are shown below the lines. B. Results of the broken-stick analysis of rRNA intron distribution. The results of the simulations are shown as are the observed standard deviations for all introns or group I and spliceosomal introns individually for both SSU and LSU rRNA genes.