Reactome: A Curated Pathway Database

Addition of the fourth nucleotide on the Nascent Transcript: Second Transition (R-HSA-75869)

Species Homo sapiens


Formation of the third phosphodiester bond creates a 4-nt product. This commits the initiation complex to promoter escape. The short 4-nt transcript is still loosely associated with the RNA polymerase II initiation complex and can dissociate to yield abortive products, which are not further extended. Inhibition of ATP-hydrolysis by TFIIH does not lead to collapse of the open region any longer. The transcription complex has lost the sensitivity to single-stranded oligo-nucleotide inhibition. However, ATP-hydrolysis and TFIIH are required for efficient promoter escape. The open region ("transcription bubble") expands concomitant with the site of RNA-extension. In this case this region spans positions -9 to +4.

Locations in the PathwayBrowser
Additional Information
Compartment nucleoplasm
Inferred Entries
Orthologous events