Lodish Ch 10: Post-transcriptional Gene Control
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Questions and Answers

Pre-mRNPs that are capped, spliced, and cleaved must be _____ before they are called nuclear mRNPs.

  • elongated
  • polyadenylated (correct)
  • phosphorylated
  • transcribed

    • The RNA recognition motif is the most common RNA-binding domain in hnRNP proteins. Another name for this motif is:

  • RNA-binding domain (correct)
  • RNA motif
  • KH motif
  • all of the above

    • In an experiment you have used recombinant DNA technology to create hnRNP C protein tagged with green fluorescent protein and hnRNP A1 protein tagged with red fluorescent protein. What would you expect to see when the proteins are expressed and visualized in Xenopus cells?

  • green and red fluorescence in the nucleus (correct)
  • green fluorescence only in the cytoplasm
  • red fluorescence only in the cytoplasm
  • red fluorescence only in the nucleus

    • Mutations that affect the binding of an SR protein to an exonic splicing enhancer can cause exon skipping in some genes, producing mRNAs that when translated yield nonfunctional proteins. In addition to an RNA-binding domain, SR proteins also contain an RS domain that is involved in binding:

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

    Sequencing of small RNAs isolated from metazoan cells revealed low levels of short, capped RNAs transcribed from both the sense and antisense strands of DNA. What is the term used to describe the fact that the majority of the metazoan genome is transcribed?

    <p>pervasive transcription</p> Signup and view all the answers

    The consensus sequence for poly(A) addition is

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

    Histone mRNAs lack

    <p>all of the above</p> Signup and view all the answers

    Which process involves two transesterification reactions?

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

    Splice sites in pre-mRNA are marked by two universally conserved sequences located

    <p>at the ends of introns</p> Signup and view all the answers

    Splicing joins

    <p>two exon sequences</p> Signup and view all the answers

    The branch-point A residue involved in lariat formation is part of the

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

    Indicate the order in which the following steps occur in the production of a mature mRNA.

    <p>initiation of transcription, addition of 5′ cap, addition of poly(A) tail, splicing, transport to cytoplasm</p> Signup and view all the answers

    Components of the spliceosome include

    <p>all of the above</p> Signup and view all the answers

    This type of RNA functions in the removal of introns from pre-RNAs.

    <p>snRNA (small nuclear RNA)</p> Signup and view all the answers

    In birds, a gene encoding a Ca -activated K channel is expressed in auditory hair cells as multiple mRNAs, which encode for proteins that open at different Ca concentrations. The Ca concentration at which the channel opens allows these cells to respond to different sound frequencies. Which one of the following would explain the appearance of the various isoforms of this particular channel?

    <p>alternative splicing</p> Signup and view all the answers

    Sex-lethal protein in Drosophila can best be described as a(n)

    <p>splicing regulatory factor</p> Signup and view all the answers

    Which of the following does not require enzymes?

    <p>excision of group II introns</p> Signup and view all the answers

    RNA editing is

    <p>post-transcriptional alteration of mRNA sequences</p> Signup and view all the answers

    The export of mRNAs outside the nucleus requires several proteins that are post-translationally modified by:

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

    Some have evolved a constitutive transport element within their genome, which allows for the export of unspliced RNAs into the cytoplasm.

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

    Which of these events does not occur within the nucleus?

    <p>RNA editing in protozoans</p> Signup and view all the answers

    Which type of RNA participates in nuclear export of mRNA?

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

    Transport of unspliced HIV mRNA from the nucleus to the cytoplasm of host cells is promoted by a virus-encoded protein named

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

    The RISC complex contains which one of the following proteins?

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

    Knocking out the dicer gene in mammals would lead to a loss of:

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

    You are using a variety of techniques to study how the RISC complex differs between siRNAs and miRNAs and have found that what distinguishes an RISC complex containing an siRNA from one containing an miRNA is that:

    <p>the siRNA base-pairs perfectly with its target mRNA</p> Signup and view all the answers

    The mammalian target of rapamycin (mTOR) complex 1 plays an integral role in all but one of these processes. Which one is mTOR not directly involved in?

    <p>protein degradation</p> Signup and view all the answers

    The cell contains numerous organelles, all with specific functions, but the one that plays a key role in the digestion of ribosomes, mitochondria, and other organelles is the:

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

    Which of the following regarding the P-body is FALSE?

    <p>it is the site where polysomes form</p> Signup and view all the answers

    Cells use several ways to avoid the translation of improperly processed mRNA molecules. ____ is(are) considered mRNA surveillance mechanisms.

    <p>all of the above</p> Signup and view all the answers

    MicroRNAs play a key role in which of the following?

    <p>all of the above</p> Signup and view all the answers

    Which of the following does not take part in the degradation process of eukaryotic mRNAs?

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

    Which of the following are NOT found within the nucleus?

    <p>P-bodies</p> Signup and view all the answers

    Synthesis of pre-rRNA occurs in the

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

    The 45S pre-rRNA molecule

    <p>all of the above</p> Signup and view all the answers

    A ribozyme is an RNA sequence

    <p>all of the above</p> Signup and view all the answers

    Study Notes

    Post-transcriptional Gene Control

    • Pre-mRNA Processing: Eukaryotic pre-mRNA is processed (capped, spliced, and polyadenylated) before becoming mature mRNA.
      • Polyadenylation is crucial for nuclear mRNA.
      • The correct order for these steps is initiation of transcription, addition of 5' cap, addition of poly(A) tail, splicing, and transport to cytoplasm.
    • RNA Recognition Motif (RRM): hnRNP proteins commonly use this domain to bind RNA.
    • hnRNP Proteins: These proteins frequently bind to RNA in the nucleus.
    • Recombinant DNA Technology: Scientists can tag proteins with fluorescent proteins to observe protein locations (e.g., green fluorescent protein, red fluorescent protein) in cells.
    • Exon Skipping: Mutations affecting SR protein binding to exonic splicing enhancers cause exon skipping in some genes.
      • SR proteins include an RS domain involved in protein binding.
    • Pervasive Transcription: The majority of the metazoan genome is transcribed.
    • Poly(A) Addition: The consensus sequence for poly(A) addition is AAUAAA. The poly(A) tail is downstream of the cleavage site.
    • mRNA Modifications: Histone mRNAs lack poly(A) tails, introns, and 3' UTR.
    • Splicing: Splicing involves two transesterification reactions and joins two exon sequences. Splice sites are at the ends of introns.
    • RNA Editing: This post-transcriptional modification alters mRNA sequences, it's an enzyme-dependent process.
      • RNA editing in mammals, RNA capping, and polyadenylation occur in the nucleus.
    • Nuclear Export: mRNA export from the nucleus requires proteins (e.g., proteins post-translationally modified by phosphorylation).
    • Sex-lethal Protein: A splicing regulatory factor in Drosophila.
    • Cytoplasmic Mechanisms:
      • RISC complex contains Argonaute proteins.
      • Knocking out dicer results in loss of miRNAs.
      • mTOR complex participates in polypeptide chain initiation and ribosome biogenesis, but not protein degradation.

    Cytoplasmic Mechanisms of Post-transcriptional Control

    • Oocyte Storage: Multicellular animal oocytes store mRNAs for early development.
      • These mRNAs have short poly(A) tails, preventing translation until fertilization. After fertilization, poly(A) tails lengthen supporting translation.

    RNA Processing and Locations

    • Nucleus: Contains locations such as Cajal bodies, histone locus bodies, and nucleoli.
      • Splicing and capping are processed here, but P-bodies are located in the cytoplasm.
    • Nucleolus: The site of pre-rRNA synthesis.
    • mRNA Stability: The cell has surveillance mechanisms such as nonsense-mediated decay, non-stop decay, and no-go decay.

    Processing of rRNA and tRNA

    • Pre-rRNA Synthesis: Occurs in the nucleolus.
    • pre-rRNA Molecule: The 45S pre-rRNA is encoded by tandemly arranged genes and is methylated on specific bases.
    • Ribozymes: RNA sequences with catalytic ability to cleave RNA, found in spliceosomes.

    Other Important Points

    • Multiple mRNAs: A single gene may produce multiple mRNAs via alternative splicing, resulting in various protein isoforms.
    • mRNA Surveillance Mechanisms: Mechanisms (e.g., nonsense-mediated decay) are utilized to prevent the translation of incorrectly processed mRNAs.

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    Lodish 8e Ch 10 Test Bank PDF

    Description

    This quiz covers key concepts of post-transcriptional gene control, focusing on eukaryotic pre-mRNA processing, hnRNP proteins, and recombinant DNA technology. Test your knowledge on processes such as exon skipping and the roles of RNA recognition motifs. Dive into the fascinating mechanisms that regulate gene expression at the RNA level.

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