Figure 1. Comparison of the yeast and mammalian splice site consensus sequences. WebLogo [ 14] representation of the 5′ splice site (5′SS), branchpoint (BP), and 3′ splice site (3′SS; the BP position is indicated with an asterisk) DNA sequence from yeast and mammalian introns. The 256 yeast intron sequences were obtained from the CYGD‐Intron database (http://mips.helmholtz‐muenchen.de/proj/yeast/reviews/intron/Intron_databases.html); the mammalian sequences were taken from the previously identified mammalian and viral BP sequences presented in Gao et al. [ 15] and the 5′SS and 3′SS consensus sequences [ 16].

Figure 2. Yeast introns are typically shorter than those observed in mammals. The 256 introns listed in the CYGD‐Intron database are plotted as a function of length. The precise cut‐offs for the large (1002–561 nt), medium (560–146 nt), and short (145–52 nt) intron lengths are arbitrary.

Figure 3. Synthetic lethal screen. (a) Overall scheme for the synthetic lethal analysis illustrated using the mud2::KAN‐msl1 mutant pair. Haploid yeast bearing the nonlethal mud2::KAN null allele plus the ade3 and ura3 phenotypic markers are transformed with a plasmid containing the wild‐type copies of MUD2, ADE3, and URA3. This strain forms red colonies that sector white stripes due to spontaneous plasmid loss. Plasmid loss also renders the strain resistant to the anti‐metabolite 5‐FOA, and makes the strain autotrophic for uracil. After mutagenesis, solid red colonies are identified as putative nonsectoring synthetic lethal mutants. The synthetic lethal mutants are unable to grow on 5‐FOA plates, since these are nonviable in the absence of the plasmid‐based URA3 gene and remain uracil prototrophs; (b) Synthetic lethal mutants are individually viable (e.g., mud2::KAN, MSL1; MUD2, msl1), but lethal when combined into the same genetic background (mud2::KAN msl1).

Figure 4. Prp38 interactions with the spliceosome and factors implicated in histone modification and chromosome packaging. A BioPIXIE representation of the combined genetic and biochemical evidence linking Prp38 function with other yeast proteins. The weighted value of evidence (strength of interaction) is illustrated in the color bar, with the splicing factors clustering to the right and the proteins involved in histone modification or chromatin structure clustering to the left. Uncharacterized genes are shown in the red ovals.