Genes promotor site

RNA-polymerase has left the operater-promotor site, and has started to transcribe the leader region as It proceeds In the direction of the first structurai gene of the operon (component I of anthranilate synthetase). The start codon for the ieader peptide has appeared, a ribosome has become attached, and transiation has started. 

Sheikh MS, Carrier F, Johnson AC et al. (1997) Identification of an additional p53-responsive site in the human epidermal growth factor receptor gene promotor. Oncogene 15 1095-1101... 

Fig. 5.3. Schematic representation of die display vector pASKIntlOO. fl, fl replication origin cat, chloramphenicol resistance marker tetR, tetracycline repressor encoding gene tetP/O, tetracycline promotor/operator region colEl, ColEl replication origin intimin, truncated eaeA gene of EHEC 0157 H7. Unique Ava I (Sma I, Xma I) and Bam HI restriction sites allow die in-frame fusion of genes encoding various passenger domains, as described in furdier detail in Wentzel et al. [7].

The pWHA43 plasmid contains 3.9 kbp and replicates with the pMBl origin of replication. The plasmid was constructed with an insert of cDNA encoding met-prochymosin under the control of a tandem lac-trp promotor operator arrangement as described in (1). The prochymosin gene was inserted just upstream from the ampicillin resistance gene without a transcription terminator sequence between, but with the RNA polymerase binding site for amp also intact, so that presumably amp is transcribed from both the lac-trp and natural amp promotors. 

The Trp repressor controls the transcription of a total of five enzymes required for the biosynthesis of tryptophan (Fig. 1.15a). The genes for the five enzymes are encoded in a single operon, whereby the binding site for the Trp repressor overlaps with the promotor. The bound repressor blocks the RNA polymerase s access to the promotor, thereby inhibiting transcription. 

Transcription initiation in procaryotes is controlled via promotors and regulatory DNA sequences located near the promotor. The role of the promotor is to provide a defined association site for the RNA polymerase and to correctly orient it. The binding of the RNA polymerase to its promotor is controlled by the sigma factor, a component of the RNA polymerase holoenzyme. The sigma factor selects which genes are to be transcribed by specifically recognizing the promotor sequence and structure and by allowing the RNA polymerase to form a transcription-competent complex at the transcription start site. 

Most promotors of of class II genes share three common features (Fig. 1.20A) the transcriptional start site, the TATA box, and sequences bound by transcriptional regulators. A typical core promotor containing the start site and the TATA box encompasses ca. 100 bp. 

Expression of IBABP and ASBT is regulated by the famesoid X receptor (FXR), a nuclear orphan receptor (246, 247). A specific binding site for F3 was found on the promotor region of the IBABP gene, named bile acid response element (BARE) (248). The response was greatest in the presence of chenodeoxy-cholic acid (CDCA), whereas cholic acid was much less effective and the secondary bile acids deoxycholic and lithocholic acid had variable responses. 

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