5. Below is a list of proteins and nucleic acid sequences involved in transcript

Question

5. Below is a list of proteins and nucleic acid sequences involved in transcription and RNA modification. • -25 • Enhancer • rut • Group I intron • -35 • GC box • TFIID • snRNP • Silencer • NusA

a. Which of the above is found in the bacterium Escherichia coli?

b. Which of the above is found in the yeast Saccharomyces cerevisiae?

c. Which of the above is involved in transcription initiation?

d. Which of the above is involved in the transcription termination?

e. Which of the above is a DNA sequence

Explanation / Answer

Q.a Ans- rut (40 nucleotide long RNA sequence containing more C residues) site found on bacterial RNA where Rho factor binds for transcription termination in E.coli. -35 (TTGACA box)is consensus sequence found in bacteria that works as strong promoter. NusA is involved in antitermination process.

QB Ans:- Saccharomyces cerevisiae is eukaryote so it has all trnscriptional proteins and DNA sequences required by Eukaryotes it include- -25 DNA sequence, GCbox, silencer, Enhancer, Group I intron, SnRNP, TFIID,

Q.C ans- In eukaryotes -25 is position of TATA box promoter element and GC box, is also promoter element necessary for transcription initiation. Enhancer(upstream activator sequences) and silencer( repressing elements) are regulatory sequences involved in efficient transcription where activators and repressors bind and regulate transcription from core promoter(initiation). TFIID is a transcription factor(multi subunit complex) which recognizes TATA element. A particular component of TFIID binds to TATA DNA sequence which is callled as TATA binding protein(TBP). It helps in formation of preinitiation comlex.

Q.4 rut site involved in transcription Rho dependent termination in prokaryotes- rho factor is helicase(5'-3' helicase activity) like hexameric protein that binds RNA at rut site(40 nucleotide long RNA sequence containing more C residues) and disrupts H bonding between DNA- RNA hybrid and transcription is terminated.   

Q.5 -25 is TATA box (promter), Enhancer, silencer DNAsequcence on eukaryotic DNA. -35 is TTGACA box(promoter) DNA sequence on prokaryotic DNA.

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