Proposed path of the pre-mRNA in the human C complex. (A) Class average of EM images of the C complex in the dominant view, showing the pre-mRNA positions located in this work. (B) Projection of all four localized pre-mRNA sites onto the 3D structure of the C complex as reconstructed by Golas et al. (2010). The location of the 5′ end of exon 1 is taken from Golas et al. (2010), as is their proposed area of the catalytic center (pink area). A possible position of the branch-point adenosine (that fits the localization data), as well as a likely path of the pre-mRNA splicing intermediates, is superimposed on the structure. The numbers indicate the structural domains of the C complex. (C) Locations and path of the pre-mRNA, as in B but projected onto the 3D structure of complex C showing also the fitted 3D structure of the 35S U5 snRNP (from Golas et al. 2010).
