Complex sentence: When a transcript attains the threshold length of ten nucleotides and enters the RNA exit channel, the polymerase breaks its interactions with the promoter elements and any regulatory proteins associated with the initiation complex that it no longer needs.
Split into simpler sentences: When a transcript attains the threshold length of ten nucleotides, it enters the RNA exit channel. The polymerase breaks its interactions with the promoter elements and any regulatory proteins associated with the initiation complex that it no longer needs.