Initiation of transcription in Escherichia coli : effect of inhibitors

Abstract

Transcription is the foremost event in gene expression in which the newlineenzyme RNA polymerase copies the genetic information from DNA to RNA. newlineThe most crucial step in the process is the initiation of transcription because it newlineis at this step that the RNA polymerase selects the gene to be transcribed. newlineBesides, the rate of transcription is also regulated at this step in the majority of newlinegenes. Transcription has been studied extensively in both prokaryotes and newlineeukaryotes. Still many aspects of the molecular mechanisms behind the newlineinitiation and subsequent steps in this process remain obscure. One approach newlineto this problem is the use of specific inhibitors that affect particular steps in newlinetranscription. newlineThe work presented in this thesis includes the studies on the action of newlineinhibitors that act at the initiation step of transcription in Escherichia coli. The newlinestudy was mostly focussed on the action of the antibiotic rifampicin. Besides newlinethe inhibitory action of seminalplasmin, a 6kd protein on transcription newlineinitiation was also studied briefly .. newlineChapter I is an overVIew of the current state of knowledge on the newlineinitiation of transcription in E. coli. During initiation, the RNA polymerase newlinerecognizes the start signal for transcription called the promoter, resulting in newlinethe formation of a closed promoter complex. The closed promoter complex newlineisomerases into an open promoter complex by a partial melting in of the newlinepromoter DNA accompanied by conformational changes in the RNA newlinepolymerase. The open promoter complex binds the nucleotide substrates and newlineX newlinestarts the synthesis of an RNA chain. After the synthesis of a short RNA newlinechain, the transcription complex enters the elongation phase in which the newlineRNA chain is elongated with full processivity, followed by chain-termination. newlineThough the steps leading to the formation of an open complex has been studied newlineextensively, the subsequent steps in transcription initiation is not very well newlineknown.