Much progress has been made in understanding the dynamic nature of initiation, elongation, and RNA processing factor associations with RNAPII. While some factors, such as the Mediator and the GTFs, remain at the promoters of transcribed genes to facilitate initiation and reinitiation, many factors, like the Pafl complex and factors required for 5' and 3' end processing of the mature mRNA join RNAPII shortly after initiation and accompany the enzyme along the transcribed region of the gene. The presence of these factors, and the changing patterns of phosphorylation of the RNAPII CTD, serve to recruit additional elongation and processing factors to RNAPII. The dynamic association of these factors is necessary for the cycle of transcription, resulting in a mature mRNA ready for export to the cytoplasm and translation. Although it is now clear that there is extensive cross-talk between these factors important for both transcription, and post-transcriptional processing, we are still uncovering the complex associations between these factors and their effects on RNAPII.

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