A long T-A tract in the upp initially transcribed region is required for regulation of upp expression by UTP-dependent reiterative transcription in Escherichia coli

Mutation in the promoter sequence of the upp initially transcribed region sequence shortens the T-A tract to different lengths ranging from seven to two base pair. The effect of the mutations on upp expression and regulation reveal that a very long T-A tract of seven to eight base pair is required for regulation.