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Abstract:
After transcription initiation, RNA polymerase (Pol) II escapes from the promoter and recruits elongation factors. The molecular
basis for the initiation-elongation factor exchange during this transition remains poorly understood. Here, we used chromatin
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 occupancy
for Abd1 peaks at110 nucleotides downstream, and occupancy for the cap-binding complex (CBC) rises subsequently.
Abd1 and CBC are important for recruitment of the kinases Ctk1 and Bur1, which promote elongation and capping enzyme
release. These results suggest that cap completion stimulates productive Pol II elongation.
