Pictoral representations of (A) proteins shown to interact with yeast Prp8p, (B) gene expression coupled with pre-mRNA splicing, and (C) three purified Prp8-containing protein complexes involving the nuclear receptor activated promoter VDR (Zhang et al. 2003), the transcription elongation complex (Kameoka et al. 2004) and the spliceosome (Makarov et al. 2002). (Gray circle) RNA pol II; (rectangle and red oval) the spliceosome. The interchromatin granular clusters (IGC), or “speckles” as they are also known, store/assemble the RNAPII and splicing factors. Upon chromatin remodelling, the DNA becomes accessible, the RNAPII/spliceosome proteins assemble on the perichromatin fibrils (PF) and produce pre-mRNA. After removal of the intron the mRNA is exported through the nuclear pore (NP) for translation and RNAPII/spliceosome proteins are stored or reassembled in the IGCs.
