Fig. 6: Model for Sen1-dependent termination of Pol II transcription.

Sen1 diffuses in solution to bind to Pol II TEC (k₊) and then translocates along the RNA transcript at ∼80 nt s⁻¹ until it reaches the Pol II, forming a Sen1-Pol II TEC intermediate. This intermediate hydrolyzes a single ATP (k₂) to dissociate Sen1 and RNA from the complex, resulting in release of only approximately 1/3 of Pol II molecules from the DNA. The time required for Sen1 to cause termination increases if the transcription bubble cannot be rewound. Sen1 then translocates along the released RNA transcript (at ∼80 nt s⁻¹) until complete dissociation. Of the 2/3 Pol II TECs retained to DNA after termination, about half undergo 1D diffusion along DNA in the post-termination state.