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. Author manuscript; available in PMC: 2015 Jan 14.
Published in final edited form as: Chem Rev. 2013 Aug 6;113(11):8583–8603. doi: 10.1021/cr400105n

Figure 8. Pol II termination pathways in yeast and human.

Figure 8

The heptad repeat in the CTD is illustrated such that white circles are unphosphorylated and red circles are phosphorylated residues. Yeast Pol II can undergo termination mediated by the Nrd1/Nab3/Sen1 complex, which recognizes sequence elements in the transcript. In human, promoter proximal paused Pol II can be terminated by TTF2 unless Gdown1 is present. Once either yeast or human elongation complexes pass a Poly(A) signal and the nascent transcript is cleaved, termination is facilitated by the degradation of the nascent transcript by Rat1 in yeast or its homolog Xrn2 in human. A conformational change of the elongation complex and Pcf11 also promote termination.