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. 2019 May;11(5):a032391. doi: 10.1101/cshperspect.a032391

Figure 2.

Figure 2.

Composition of the spliceosome. Protein composition (left), small nuclear RNA (snRNA) secondary structure (middle), and three-dimensional structure (right) of yeast spliceosome components as they assemble on precursor messenger RNA (pre-mRNA) substrates. Each of the five small nuclear ribonucleoprotein particles (snRNPs) is shown with shades of distinct colors (U1, magenta; U2, green, U4, yellow; U5, blue; U6, red). For each snRNA, important secondary structure elements are labeled. The structure of the isolated U2 snRNP remains unknown, and in its stead, we show the yeast U2 snRNP structure bound to pre-mRNA (black) (yeast B complex, PDB 5NRL). For the nineteen complex (NTC) and nineteen-related (NTR), the three-dimensional structures found in the C complex are shown. The NTC forms a complex in isolation (Chan and Cheng 2005), whereas the NTR proteins are likely to join the spliceosome separately. The yeast U1 snRNP (PDB 5UZ5), the yeast U2 snRNP (PDB 5NRL), yeast tri-snRNP (PDB 5NRL), and the NTC and NTR in the Bact complex (PDB 5GM6) structures are shown. SL, stem loop.