Complex sentence: In this regulation, the riboswitch controls transcription that interferes with the transcription of the gene, perhaps caused by clashes between two RNA polymerase units as they simultaneously transcribe the same DNA.
Split into simpler sentences: In this regulation, the riboswitch interferes with transcription of the gene. The mechanism is uncertain but may be caused by clashes between two RNA polymerase units as they simultaneously transcribe the same DNA.