P (2013) Cap completion and C-terminal repeat domain kinase recruitment underlie the initiation-elongation transition of RNA polymerase II. Mol Cell Biol 33

After transcription initiation, RNA polymerase (Pol) II escapes from the promoter and recruits elongation factors. The molecu-lar basis for the initiation-elongation factor exchange during this transition remains poorly understood. Here, we used chroma-tin immunoprecipitation (ChIP) to elucidate the initiation-elongation transition of Pol II in the budding yeast Saccharomyces cerevisiae. We show that the early Pol II elongation factor Spt5 contributes to stable recruitment of the mRNA capping enzymes Cet1, Ceg1, and Abd1. Genome-wide occupancy for Cet1 and Ceg1 is restricted to the transcription start site (TSS), whereas oc-cupancy for Abd1 peaks at110 nucleotides downstream, and occupancy for the cap-binding complex (CBC) rises subse-quently. Abd1 and CBC are important for recruitment of the kinases Ctk1 and Bur1, which promote elongation and capping en-zyme release. These results suggest that cap completion stimulates productive Pol II elongation. Transcription of protein-coding genes by RNA polymerase(Pol) II begins with assembly of an initiation complex at the promoter. As the RNA grows, initiation factors dissociate from Pol II, and elongation factors are recruited (1–3). The initiation-elongation transition begins when the nascent RNA grows to about 12 nucleotides (nt), which releases initiation factor TFIIB (4, 5). Release of initiation factors frees the Pol II clamp domain, which binds the conserved elongation factor Spt5 (6, 7). Here, w