대장균에서 많은 수의 플라스미드에 존재하는 rnpB 유전자 전사의 성장기의 따른 조절 작용

Abstract

The Escherichia coli rnpB gene encodes M1 RNA, the catalytic component of RNase P which is a processing enzyme for tRNA maturation. Biosynthesis of M1 RNA is known to be stringently regulated. The rnpB transcription under different growth phases of E. coli was examined using the truncated rnpB in the multicopy plasmids which could generate the metabolically unstable M1 RNA transcript. Biosynthesis of this RNA was directly analyzed during the transition from the exponential phase of growth to the stationary phase. During the transition the rnpB transcription became repressed. The discriminator motif CGCC adjacent to the transcription start-point of the rnpB gene was altered to the TATT using site-directed mutagenesis. The modified promoter containing the mutated discriminator was at least partially resued from this growth phase-dependent repression of the rnpB transcription. The results clearly show that the discriminator motif play a key role in control of the rnpB transcription under different growth phases.