RNA Processing and Maturation
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Questions and Answers

What is the purpose of the 7-methylguanosine cap added to RNA?

  • To aid in ribosome binding for translation
  • To protect the RNA from degradation
  • To facilitate the export of RNA from the nucleus
  • All of these options (correct)

    • Which enzyme adds the poly(A) tail to the mRNA?

  • Polyadenylate polymerase (correct)
  • Spliceosome
  • Endonuclease
  • RNA Polymerase II

    • Where does the polyadenylation process occur in eukaryotic cells?

  • Mitochondria
  • Cytoplasm
  • Nucleus (correct)
  • Endoplasmic reticulum

    • What is removed during the splicing process of RNA?

    <p>Introns</p> Signup and view all the answers

    Which polymerase is responsible for synthesizing mRNA in eukaryotes?

    <p>RNA Polymerase II</p> Signup and view all the answers

    What sequence do RNA polymerase II and endonuclease recognize for mRNA cleavage?

    <p>AAUAAA</p> Signup and view all the answers

    What is the primary function of RNA Polymerase II?

    <p>Responsible for synthesis of mRNA</p> Signup and view all the answers

    Which transcription factor is thought to be involved in DNA melting?

    <p>TFIIE</p> Signup and view all the answers

    What sequence is commonly found approximately -30 from the start site in RNA Pol II promoters?

    <p>TATAAA</p> Signup and view all the answers

    Which protein specifically recognizes the TATA box?

    <p>TBP</p> Signup and view all the answers

    During the transcription assembly process, which transcription factor binds to RNA Pol and targets it to the promoter?

    <p>TFIIF</p> Signup and view all the answers

    What happens to RNA Pol II at the termination of transcription?

    <p>Phosphate is removed</p> Signup and view all the answers

    Which factor unwinds DNA at the promoter during transcription initiation?

    <p>TFIIH</p> Signup and view all the answers

    What role does TFIIH play in the initiation of transcription besides unwinding DNA?

    <p>Phosphorylates RNA Pol II</p> Signup and view all the answers

    What is the function of the 5' cap of mRNA?

    <p>Protects mRNA from 5' exonuclease degradation</p> Signup and view all the answers

    What forms the 5' cap of eukaryotic mRNA?

    <p>GTP</p> Signup and view all the answers

    Which sequences remain in mature mRNA after splicing?

    <p>Exons</p> Signup and view all the answers

    What sequence is added at the 3' end of eukaryotic mRNA?

    <p>Poly-A tail</p> Signup and view all the answers

    Which enzymes are involved in capping the 5' end of mRNA?

    <p>Capping enzymes tethered to the C-terminal domain of polymerase II</p> Signup and view all the answers

    What is the nature of introns?

    <p>Introns are non-coding sequences located between coding sequences.</p> Signup and view all the answers

    Study Notes

    RNA Processing

    • RNA processing involves three major modifications: addition of 7-methylguanosine caps to 5' termini, excision of non-coding intron sequences, and addition of poly(A) tails to 3' ends
    • These modifications occur in the nucleus prior to transport to the cytoplasm

    Eukaryotic RNA Polymerases

    • Three different RNA polymerases are present in eukaryotes: RNA polymerase I, RNA polymerase II, and RNA polymerase III
    • RNA polymerase I synthesizes pre-ribosomal RNA (precursor for 28S, 18S, and 5.8 rRNAs)
    • RNA polymerase II is responsible for the synthesis of mRNA
    • RNA polymerase III makes tRNAs and some small RNA products

    Assembly of RNA Polymerase

    • Assembly is initiated by interaction of TATA-binding protein (TBP) with the promoter
    • Two transcription factors (TFIIA and TFIIB) bind to the promoter
    • TFIIE and TFIIH bind to the promoter, where TFIIE is involved in DNA melting and TFIIH has helicase activity

    RNA Polymerase II Promoters

    • Conserved sequences include the TATA box and the Inr
    • TATA box is located at -30 and has the sequence TATAAA
    • Inr is located at +1 and has the sequence YYANTYY

    RNA Strand Initiation and Promoter Clearance

    • Kinase activity in TFIIH phosphorylates the polymerase, allowing it to escape the promoter
    • Initially, 60-70 RNA nucleotides are synthesized
    • Then, TFIIE and TFIIH are released, and the process moves to elongation

    Elongation, Termination, and Release

    • TFIIF remains attached to RNA Pol II
    • Elongation factors help with efficiency
    • E longation factors stop pausing and regulate post-transcriptional processing
    • At termination, the phosphate is removed

    Capping the 5' of mRNA

    • Capping protects mRNA from 5' exonuclease degradation
    • Cap is 7-methylguanosine linked to 5' end of mRNA
    • Capping occurs early in transcription

    Introns

    • Introns are non-coding sequences located between coding sequences
    • Introns are removed from the pre-mRNA and are not present in the mRNA
    • Exons are composed of the sequences that remain in the mature mRNA after splicing

    Polyadenylation

    • A poly(A) tail is built at the 3' end of mRNA
    • Poly(A) tail is synthesized by polyadenylate polymerase
    • Poly(A) tail is a run of adenines at the 3' end of mRNA

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    Description

    This quiz covers the process of RNA processing, including transcription, capping, cleavage, polyadenylation, and splicing to form mature mRNA. Understand how the poly(A) tail is added to the mRNA.

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