(The) effect of C5 protein on transcription of the rnpB gene

Abstract

Escherichia coli RNase P, a tRNA processing enzyme, is composed of C5 protein and M1 RNA which are encoded by the rnpA and rnpB genes, respectively. To examine the growth-phase dependent control of the rnpB gene harbored on a multicopy plasmid a combination of Northern analysis for RNA determination and Southern analysis for plasmid DNA determination was used. The relative transcription activity of rnpB was represented by a ratio of the relative amount of the transcript to that of the plasmid DNA during bacterial growth. The rnpB gene transcription increased rapidly with time during exponential growth but started to decrease before the transition period of an exponential growing cell culture into the stationary phase. The accurate role of the C5 protein in vivo has not been discovered, but it has been suggested that the synthesis of C5 protein and M1 RNA components of RNase P are coordinately regulated. As a first attempt to clarify the coordinate regulation, it was examined how transcription of the rnpB gene was changed when synthesis of C5 protein increased by using the cloned rnpA gene. The elevated expression of C5 protein resulted in the increase of transcription of the rnpB gene at least in cells growing at the stationary phase. However, the results of in vitro transcription and footprinting suggested that C5 protein neither interacts with a transcription initiation complex formed by E. coli RNA polymerase in the rnpB promoter nor directly binds to the rnpB promoter.