<P> Mechanistically, promoter escape occurs through DNA scrunching, providing the energy needed to break interactions between RNA polymerase holoenzyme and the promoter . </P> <P> In bacteria, upon and following promoter clearance, the σ factor is released according to a stochastic model . </P> <P> In eukaryotes, at an RNA polymerase II - dependent promoter, upon promoter clearance, TFIIH phosphorylates serine 5 on the carboxy terminal domain of RNA polymerase II, leading to the recruitment of capping enzyme (CE). The exact mechanism of how CE induces promoter clearance in eukaryotes is not yet known . </P> <P> One strand of the DNA, the template strand (or noncoding strand), is used as a template for RNA synthesis . As transcription proceeds, RNA polymerase traverses the template strand and uses base pairing complementarity with the DNA template to create an RNA copy . Although RNA polymerase traverses the template strand from 3' → 5', the coding (non-template) strand and newly formed RNA can also be used as reference points, so transcription can be described as occurring 5' → 3' . This produces an RNA molecule from 5' → 3', an exact copy of the coding strand (except that thymines are replaced with uracils, and the nucleotides are composed of a ribose (5 - carbon) sugar where DNA has deoxyribose (one fewer oxygen atom) in its sugar - phosphate backbone). </P>

Messenger rna (mrna) is transcribed from a section of dna and the process is called transcription