Figure 5.

Models for XRN2-dependent and DSE-dependent transcription termination. XRN2 is recruited to Pol II on both XDT and non-XDT genes and facilitates Pol II accumulation at the gene ends, possibly by promoting pausing. On XDT genes, XRN2 degrades a nascent transcript following 3′ end cleavage and terminates Pol II. On non-XDT genes, Pol II transcribes beyond the pA site up to a DSE, which induces Pol II termination. Cleavage at the pA site separates the nascent mRNA from the downstream fragment; XRN2 might contribute, with other RNases, to the degradation of the latter. Different Pol II colors illustrate presumed differences in TEC properties and/or composition, determined by promoters, which result in differences in termination modes. See the text for details.