During eukaryotic mRNA 3' end processing, cleavage and polyadenylation require specific sequence signals in the pre-mRNA. Which sequence serves as the primary signal recognized by the cleavage and polyadenylation specificity factor (CPSF)?

• A GU-rich downstream sequence element
• B TATA box
• C CAAT box
• D AAUAAA hexamer ✓

Explanation

The AAUAAA hexamer located 10 to 30 nucleotides upstream of the cleavage site is the core polyadenylation signal recognized by CPSF. The GU-rich downstream element is recognized by cleavage stimulation factor (CstF) but is secondary. The CAAT box and TATA box are promoter elements involved in transcription initiation, not 3' end processing.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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