Termination

Termination phase overview

The third step of transcription is termination, which follows initiation and elongation.

Purpose of termination

Termination signals the end of transcription, stopping the synthesis of the primary RNA transcript.

Trigger for termination

RNA polymerase reaches a termination sequence in the DNA, which indicates the end of the coding region.

Nature of termination sequences

Termination sequences are not highly conserved; they vary among different genes.

Action of RNA polymerase at termination

When RNA polymerase encounters the termination signal, it releases from the DNA template strand.

Role of Rho proteins

Rho proteins (named after the Greek letter ρ) can bind near the termination site and help dislodge RNA polymerase from DNA.

Summary of termination process

Polymerase keeps transcribing until it receives a DNA signal to stop, then detaches—sometimes assisted by Rho proteins.

After termination

The primary transcript (pre-mRNA) is released and ready for processing: intron splicing, 5′ cap addition, and poly-A tail addition.

Next step in the central dogma

After processing, the mature mRNA moves on to translation, where it directs protein synthesis.