1. Bacterial transcription initiation a. What are the major components of a bact
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Question
1. Bacterial transcription initiation
a. What are the major components of a bacterial promoter? Do you understand their nomenclature (i.e. how are they related to the transcription start site)?
b. What is the function of each promoter element during initiation?
c. What sequence-based factors contribute to promoter strength?
d. Why are there multiple sigma factors? How do they function to turn on different genes?
e. Why are short (<10 nt) abortive products possible during transcription intiation? What happens to RNAP when these products are released?
f. What changes in the RNAP holoenzyme occur following promoter escape?
Explanation / Answer
1. Bacterial transcription initiation
a. What are the major components of a bacterial promoter?
There are two sequences, in the form of pribnow box present at 10 as well as 35 nucleotides upstream from the site of transcription. There is presence of a TATAAT sequence.
b. What is the function of each promoter element during initiation?
Function of the Tata box is to specify the other promoters where the transcription should be beginning, as it is located 25-35 nucleotides from the start site. The pribnow box is identified by the bound RNA pol subunit at the time of transcription initiation.
c. What sequence-based factors contribute to promoter strength?
The sequence of the promoter would be determining the strength of the promoter. When promoters have consensus sequences, when there are strong upstream elements, it would be contributing to the strength of the promoters. The tho factors recognise the specific promoter motifs and directs the complex towards the target sequence.
d. Why are there multiple sigma factors? How do they function to turn on different genes?
Sigma factors are the proteins required for transcription initiation. The number of sigma factors would be varying between bacterial species. There are 7 factors in the e.coli. Sigma factors would be executing the DNA transcription present on the template strand as it is there along with the rna polymerase holoenzyme. After completion of of transcription, sigma factor Leave the complex. These are:
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