Transcription quality control at the promoter-proximal checkpoint

Transcription of protein-coding genes by RNA polymerase II involves a characteristic pausing event downstream from transcription start sites. Such promoter-proximal pausing likely represents a transcription checkpoint, which ensures proper assembly of a fully functional RNAPII elongation complex that is capable of transcribing through the chromatin environment, with correctly modified nascent pre-mRNA. Failure to negotiate this promoter-proximal checkpoint results in termination of transcription and removal of RNAPII from the DNA. This review summarizes current knowledge on the mechanisms that regulate promoter-proximal pausing, maturation of the elongation complex, and the decision of whether to license RNAPII for elongation or prematurely terminate transcription.