The 3' poly-A tail of eukaryotic mRNA is added post-transcriptionally. Which sequence element directs cleavage of the pre-mRNA and subsequent polyadenylation?
- A The TATA box located 25 nucleotides upstream of the transcription start site
- B The AAUAAA consensus sequence located 10 to 30 nucleotides upstream of the cleavage site ✓
- C The Kozak consensus sequence surrounding the AUG codon
- D The branch point adenosine within the intron
Correct answer: B. The AAUAAA consensus sequence located 10 to 30 nucleotides upstream of the cleavage site
Explanation
The highly conserved AAUAAA hexamer lies 10 to 30 nucleotides upstream of the polyadenylation cleavage site and is recognized by CPSF (cleavage and polyadenylation specificity factor). After cleavage downstream of a GU-rich sequence, poly(B) polymerase adds 200 to 250 adenosine residues without a template. The TATA box functions in promoter recognition, the Kozak sequence governs translation initiation, and the branch point adenosine participates in splicing, not polyadenylation.
Reference: Lippincott's Illustrated Reviews: Biochemistry, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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