1. You have determined there is a mutation in a strain of yeast in which a compo
ID: 149919 • Letter: 1
Question
1. You have determined there is a mutation in a strain of yeast in which a component of TFIID retains full binding activity with DNA at an elevated temperature but can no longer make contact with TFIIB (temperature sensitive mutation). Will the RNA Polymerase II enzyme complex be able to transcribe in this strain at elevated temperatures? Provide a reasonable hypothesis as to why or why not.
2. You have discovered a new protein that binds tightly to an unusual amino acid that is not used in biology and does not perform any chemical reactions on it. Provide a step-by-step plan to use this unusual amino acid to purify this new protein from a complex mixture using chromatography techniques.
Explanation / Answer
1. Eukaryotic transcription initiation begins with the binding of transcription factors along with RNA polymerase II to the promoter region of a gene and forms a pre-initiation complex. The first transcription to be recruited to the promoter site is TFIID, which binds to TATA box, followed by TFIIA and TFIIB. TFIIB, then interacts with TFIIF and recruits RNA pol II to the promoter.
At elevated temperature, TFIID will bind to the promoter region in this yeast strain, but failure of TFIID to make contact with TFIIB, will block the recruitment of other transcription factors (TFIIF, TFIIE, TFIIH,) along with RNA pol II. Thsi will lead to no transcription by RNA pol II (due to no formation of pre initiation complex) in this yeast strain at elevated temperatures.
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