Newly initiated RNA encounters a factor involved in splicing immediately upon emerging from within RNA polymerase II

摘要: We employed RNA-protein cross-linking to map the path of nascent RNA as it emerges from within polymerase II. A UV-cross-linkable uridine analog was incorporated at two positions first five nucleotides transcript. Only largest subunits II cross-linked transcript in complexes containing 17-24-nucleotide (nt) RNAs. Extension 26 or 28 nt revealed an additional strong cross-link splicing factor U2AF65. In U17 complexes, which is still contained polymerase, U2AF65 tightly bound. contrast, more loosely bound C28 transcription about 10 have emerged polymerase. Cross-linking a complex eliminated by addition excess oligonucleotide consensus binding site, but not displaced nonconsensus RNA. These findings indicate that shifts protein-protein protein-RNA interactions During one particular template low UTP concentration, pauses just after synthesizing segment site. Dwell time this pause site significantly and specifically reduced recombinant reaction. Therefore, association with may function only deliver also modulate efficient elongation.