DETERMINATION OF INTRINSIC TRANSCRIPTION TERMINATION EFFICIENCY BY RNA-POLYMERASE ELONGATION RATE

Transcription terminators recognized by several RNA polymerases includ e a DNA segment encoding uridine-rich RNA and, for bacterial RNA polym erase, a hairpin loop located immediately upstream. Here, mutationally altered Escherichia coli RNA polymerase enzymes that have different t ermination efficiencies were used to show that the extent of transcrip tion through the uridine-rich encoding segment is controlled by the su bstrate concentration of nucleoside triphosphate. This result implies that the rate of elongation determines the probability of transcript r elease. Moreover, the position of release sites suggests an important spatial relation between the RNA hairpin and the boundary of the termi nator.