Reaction: Addition of the fourth nucleotide on the nascent HIV-1 transcript: Second Transition
- in pathway: RNA Polymerase II HIV Promoter Escape
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.
Reaction - small molecule participants:
PPi [nucleoplasm]
NTP [nucleoplasm]
Reactome.org reaction link: R-HSA-167113
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Reaction input - small molecules:
nucleoside 5'-triphoshate(4-)
Reaction output - small molecules:
diphosphate(3-)
Reactome.org link: R-HSA-167113