Poly A dependent termination: This type of termination are basically coupled with the RNA maturation process in which 3’ end of nascent RNA undergo polyadenylation and cleavage, and these 3 ‘ end processing reaction are carried out in two steps:

Transcription of poly A followed by cleavage of nascent transcript, and then the upstream product is polyadenylated and downstream product is degraded. Basically 3’ end processing starts when the cis acting element in the Poly A site of nascent RNA transcript is recognised by the binding factors .when these factors bind at 3’end, it form a very complex structure  which result in high shear forces consequently processing slow down which causes disruption of  polymerase ll and DNA –RNA hybrid complex; and ultimately termination occurs (Figure 28.12)

Figure 28.12 : Termination of RNA Pol II Transcription