Initiation. Activation of the promoter occurs with the help of a large protein - the TATA factor, so-called because it interacts with a specific nucleotide sequence of the promoter-TATAAA- (TATA box). The addition of the TATA factor facilitates the interaction of the promoter with RNA polymerase. Initiation factors cause a change in the conformation of RNA polymerase and provide the unwinding of approximately one turn of the DNA helix, i.e. a transcriptional fork is formed in which the matrix is available to initiate RNA chain synthesis.
Elongation. Elongation factors increase the activity of RNA polymerase and facilitate the separation of DNA chains. The synthesis of the RNA molecule goes from the 5'- to the 3'-end of the complementary template DNA strand. At the elongation stage, in the region of the transcriptional fork, approximately 18 nucleotide pairs of DNA are simultaneously separated. The growing end of the RNA chain forms a temporary hybrid helix, about 12 pairs of nucleotide residues, with a DNA template chain. As the RNA polymerase moves
Termination. The unwinding of the DNA double helix in the region of the termination site makes it available for the termination factor. The synthesis of RNA is completed in strictly defined areas of the matrix — terminators (termination sites).