Question

what are the roles of transcription factors and the promoter reguon in transcription?

Answer 1

Transcription factors are the protein that either turn on or turn off transcription of a gene. These proteins interacts with DNA and also RNA polymerases to bring upon their action. For eg. A transcription factor TFIID has a domain called TBP (TATA Binding Protein) which recognises the TATA box sequence in gene promoter and helps binding of TFIID to DNA. Later TFIID incorporates other transcription factors required for initiation of transcription in eukaryotes. Another example is TFIIH which has helicase activity and helps RNA polymerase II in unwinding of DNA for transcription.

There are many such transcription factors that either assists in transcription or halts transcription.

Promoter region in a gene is the site for binding of RNA polymerase which synthesize mRNA from DNA template.

Promoter regions has specific consensus sequences like TATA box, Pribnow box etc. which are determined by various transcription factors. Apart from being the binding site of RNA polymerase, the promoter region also tells the direction in which the DNA is to be transcribed to RNA polymerase. In eukaryotes each gene has a different promoter.

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