<P> A sigma factor is a protein needed only for initiation of RNA synthesis in bacteria . Sigma factors provide promoter recognition specificity to the RNA polymerase (RNAP) and contribute to DNA strand separation, then dissociating from the RNA polymerase core enzyme following transcription initiation . The RNA polymerase core associates with the sigma factor to form RNA polymerase holoenzyme . Sigma factor reduces the affinity of RNA polymerase for nonspecific DNA while increasing specificity for promoters, allowing transcription to initiate at correct sites . The core enzyme of RNA polymerase has five subunits (protein subunits) (~ 400 kDa). Because of the RNA polymerase association with sigma factor, the complete RNA polymerase therefore has 6 subunits: the sigma subunit - in addition to the two alpha (α), one beta (β), one beta prime (β'), and one omega (ω) subunits that make up the core enzyme (~ 450 kDa). In addition, many bacteria can have multiple alternative σ factors . The level and activity of the alternative σ factors are highly regulated and can vary depending on environmental or developmental signals . </P> <P> The transcription preinitiation complex is a large complex of proteins that is necessary for the transcription of protein - coding genes in eukaryotes and archaea . It attaches to the promoter of the DNA (e.i., TATA box) and helps position the RNA polymerase II to the gene transcription start sites, denatures the DNA, and then starts transcription . </P> <P> The assembly of transcription preinitiation complex follows these steps: </P> <Ol> <Li> TATA binding protein (TBP), a subunit of TFIID (the largest GTF) binds to the promoter (TATA box), creating a sharp bend in the promoter DNA . Then the TBP - TFIIA interactions recruit TFIIA to the promoter . </Li> <Li> TBP - TFIIB interactions recruit TFIIB to the promoter . RNA polymerase II and TFIIF assemble to form the Polymerase II complex . TFIIB helps the Pol II complex bind correctly . </Li> <Li> TFIIE and TFIIH then bind to the complex and form the transcription preinitiation complex . TFIIA / B / E / H leave once RNA elongation begins . TFIID will stay until elongation is finished . </Li> <Li> Subunits within TFIIH that have ATPase and helicase activity create negative superhelical tension in the DNA . This negative superhelical tension causes approximately one turn of DNA to unwind and form the transcription bubble . </Li> <Li> The template strand of the transcription bubble engages with the RNA polymerase II active site, then RNA synthesis starts . </Li> </Ol>

Which of the following is not part of the transcription initiation complex