The presence of the four nucleoside triphosphate in RNA enhances the binding of RNA to DNA during transcription. The nucleosides prevent the dissociation of RNA polymerase from its binding site by high salt concentration. The nucleosides also protect the RNA polymerase from alteration by heat.
Sigma factors improve the binding of RNA polymerase to the promoters. They recognize the specific promoters sites. A common type of sigma factor is sigma 70. After the start of transcription, sigma factor falls aways.
