Termination of transcription

The RNA polymerase transcribes the gene past the polyadenylation site, usually several hundred bases, before the pre-mRNA is cleaved and polyadenylated. It is not known precisely what causes the RNA polymerase to leave the DNA template. In one model, it is suggested that cleavage of the pre-mRNA leaves an unprotected short RNA chain attached to the elongating RNA polymerase. Rapid degradation of this short RNA triggers termination of transcription. In the second model, the RNA polymerase changes its elongation capacity as it passes the polyadenylation signal and this leads to termination of transcription. The change could be a loss of an anti-terminator factor bound to the RNA polymerase.