Question

Why is promoter important? Is it copied into mRNA? Using the sequence of sigma-70 promoter, describe the role of -35 and -10 sequences in formation of the initiation complex. The promoter sequence is located on which strand, coding or template? How many promoters will a polycistronic mRNA have?

Answer 1

1) A promoter sequence is important as it defines the beginnig point of any transcription process. The promoter guides the process of transcription and is on the DNA sequence. The promoter sequences are not copied

2) The -35 to -10 sequences are the consensus sequences that are located upstream from the transcription site. The -10 element is the Pribnow box or the TATA box that acts as a binding site for the transcription initiation complexes. The initiation complex binds to the specific region at the TATA box which is upstream to the site of transcription and allows recognition of the start site for the process. The sigma factors are special proteins that help the RNA polymerase to bind to the promoter sequence for the transcription.

3) The promoter sequence is located in the coding strands of the DNA.

4) A polycistronic mRNA will have multiple genes but only one promoter.