HIV-1 Transcription Initiation Authored: Matthews, L, Rice, AP, 2005-07-27 00:00:00 Edited: Matthews, L, 2005-07-26 23:29:22 Formation of the open complex exposes the template strand to the catalytic center of the RNA polymerase II enzyme. This facilitates formation of the first phosphodiester bond, which marks transcription initiation. As a result of this, the TFIIB basal transcription factor dissociates from the initiation complex.<p>The open transcription initiation complex is unstable and can revert to the closed state. Initiation at this stage requires continued (d)ATP-hydrolysis by TFIIH. Dinucleotide transcripts are not stably associated with the transcription complex. Upon dissociation they form abortive products. The transcription complex is also sensitive to inhibition by small oligo-nucleotides. <p>Dinucleotides complementary to position -1 and +1 in the template can also direct first phosphodiester bond formation. This reaction is independent on the basal transcription factors TFIIE and TFIIH and does not involve “full” open complex formation. This reaction is sensitive to inhibition by single-stranded oligonucleotides. GENE ONTOLOGYGO:0006367 Reactome Database ID Release 43167161 Reactome, http://www.reactome.org ReactomeREACT_6332 PathwayStep3538 PathwayStep3539 PathwayStep3540 PathwayStep3541 NTP binds active site of RNA Polymerase II in HIV-1 open pre-initiation complex Newly formed phosphodiester bond stabilized and PPi released Nucleophillic attack by 3'-hydroxyl oxygen of nascent HIV-1 transcript on the Alpha phosphate of NTP Abortive HIV-1 initiation after formation of the first phosphodiester bond