AT-rich sequence elements promote nascent transcript cleavage leading to RNA polymerase II termination.

RNA Polymerase II (PoI II) termination is dependent on RNA processing signals as well as specific terminator elements located downstream of the poly(A) site. One of the two major terminator classes described so far is the Co-Transcriptional Cleavage (CoTC) element. We show that homopolymer tracts within the human beta-globin CoTC-mediated terminator element play a critical role in Pol I termination. These short tracts, dispersed within seemingly random sequences, are strong terminator elements, and bioinformatics analysis confirms the presence of such sequences in 70% of the putative terminator regions (PTRs) genome-wide.