FIGURE 6.

Model: a role for Spt5 in cotranscriptional spliceosome assembly. In wild-type conditions (without Spt5 depletion), Spt5 facilitates cotranscriptional spliceosome assembly by promoting stable recruitment of the U5 snRNP. This may be mediated, either directly or indirectly, by the interaction between Spt5 and core members of the spliceosome, although it is unclear whether the interaction occurs already at the prespliceosome stage. Upon Spt5 depletion (indicated by the red cross), the U5 snRNP is either not recruited or does not remain stably associated, so that pre-B/B complexes or later complexes do not form, or form and then rapidly disassemble, leading to defects in splicing catalysis.