A role for the CPF 3'-end processing machinery in RNAP II-dependent gene looping.

The prevailing view of the RNA polymerase II (RNAP II) transcription cycle is that RNAP II is recruited to the promoter, transcribes a linear DNA template, then terminates transcription and dissociates from the template. Subsequent rounds of transcription are thought to require de novo recruitment of RNAP II to the promoter. Several recent findings, including physical interaction of 3'-end processing factors with both promoter and terminator regions, challenge this concept. Here we report a physical association of promoter and terminator regions of the yeast BUD3 and SEN1 genes. These interactions are transcription-dependent, require the Ssu72 and Pta1 components of the CPF 3'-end processing complex, and require the phosphatase activity of Ssu72. We propose a model for RNAP II transcription in which promoter and terminator regions are juxtaposed, and that the resulting gene loops facilitate transcription reinitiation by the same molecule of RNAP II in a manner dependent upon Ssu72-mediated CTD dephosphorylation.