Question

One form of posttranscriptional modification of most eukaryotic RNA transcripts is the addition of a poly-A sequence at the 3' end. The absence of a poly-A sequence leads to rapid degradation of the transcript. Poly-A sequences of various lengths are also added to many prokaryotic RNA transcripts where, instead of promoting stability, they enhance degradation. In both cases, RNA secondary structures, stabilizing proteins, or degrading enzymes interact with poly-A sequences.

Considering the activities of RNAs, what might be the general functions of 3-polyadenylation? Check all that apply.

A. regulation of mRNA association with cellular components, like proteins, lipids, or nucleic acids
B. regulation of mRNA splicing
C. regulation of mRNA transport to the cytoplasm
D. regulation of mRNA proofreading
E. regulation of mRNA longevity
F. regulation of introns' length

Answer 1

A,C and E are correct

Step-by-step explanation:

• Most of mature eukaryotic mRNA have 50-250 adenine residue at the 3'end, called Poly A tail
• These nucleotides are not encoded by the genome but are added after transcription, process called polyadenylation
• Polyadenylation is both template and primer independent process catalysed by polyadenylate polymerase (PAP)
• PAP uses ATP as a precursor and adds the nucleotides using same chemistry as RNA Polymerase
• Primary function of Poly A tail is to protect mRNA from exonuclease at 3' end
• It also helps in export of mature mRNA from the nucleus to the cytoplasm
• Serves as recognition signal for translation factors during translation initiation