Torpedo model for transcription termination by Pol II. The torpedo model hypothesizes that the mRNA transcript is cleaved downstream from the poly(A) addition site by the U7 snRNP. An exonuclease (Xrn2) binds the RNA remaining on the polymerase and degrades the RNA in the 5′→3′ direction, moving closer to the polymerase and eventually causing it to release the mRNA.