Several mechanisms result in termination of transcription .
In eucaryotes , investigation of termination is complicated by the rapid processing of the 3' end of transcripts. Termination of transcription plays a role in regulation of gene expression for cistrons downstream of a regulated termination site. The regulation event may activate a hidden termination signal, as in attenuation . The regulation event may repress a termination signal, as in anti-termination , seen in procaryotes , and possibly also in eucaryotes .