CH391L/S12/TranscriptionPromotersandTerminators: Difference between revisions

Terminators consist of a G+C rich dyad symmetry sequence followed by a poly (T) tract. If the terminator is bidirectional, then a poly (A) segment will be upstream to the dyad symmetry sequence. The iGEM registry has forward, reverse, and bidirectional terminators. The most important piece of a terminator is the G+C dyad sequence that will form a a hairpin loop in the RNA transcript. It has also been shown that the poly (T) tract is needed for termination to occur.

These terminators are composed A, T rich sequences as well as a two-fold symmetric DNA sequence rich in G+C. When transcribed by RNA, these sequences lead to the formation hairpin loop rich in G-C base pairs. The formation of the RNA G-C rich stem loop causes a pause in the RNA Polymerase. This pause, followed by the transcription of the poly A tail into a run of U's causes a mechanical stress and the unwinding of the RNA-DNA complex, causing the dissociation of the RNA transcript from RNA polymerase.<cite>#Wilson1995</cite> Rho-independent terminators may have a stabilization effect on the gene they succeed.