Gene Regulation and RNA Splicing in Eukaryotes
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Questions and Answers

Alternative splicing allows a single gene to produce multiple protein isoforms.

True

What are the core cis-elements involved in RNA splicing?

5' splice site, 3' splice site, branch point sequence, polypyrimidine tract

The spliceosomal _____ are crucial trans-acting factors for RNA splicing.

snRNPs

Match the following RNA-binding proteins with their roles:

<p>SR proteins = Promote splicing hnRNPs = Repress splicing</p> Signup and view all the answers

Which of the following processes is NOT subject to posttranscriptional regulation?

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

In Drosophila, splicing does not play a role in sex determination.

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

Name one modern experimental approach used to investigate posttranscriptional regulation of gene expression.

<p>RNA sequencing or CLIP-seq</p> Signup and view all the answers

Which complex is responsible for the splicing reaction in pre-mRNA?

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

The spliceosome consists only of small nuclear RNAs (snRNPs).

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

The process of joining exons and removing introns to produce mature mRNA is known as __________.

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

Match the following RNA splicing components with their functions:

<p>U1 snRNP = Binds to 5’ splice site U2AF = Stabilizes binding of proteins U5 = Interacts with both exons hnRNPs = Binds to introns and exons</p> Signup and view all the answers

What role do tissue-specific alternative splicing regulators such as RBFOX and NOVA play?

<p>They compete with core splicing factors.</p> Signup and view all the answers

The first step in the splicing mechanism involves the release of U4 and U6.

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

Name two key actions performed by RNA binding proteins like PTB in splicing regulation.

<p>Competition with core splicing factors and assembly of higher order repressive complexes.</p> Signup and view all the answers

What is the main function of the Sxl protein in females?

<p>It promotes the inclusion of a female-specific exon.</p> Signup and view all the answers

In males, the Sxl protein is produced from a functional pre-mRNA.

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

What role does the Tra protein play in females?

<p>Splicing regulator</p> Signup and view all the answers

In low iron levels, IRE binding protein binds to _____ to stabilize transferrin receptor mRNA.

<p>IRE hairpins</p> Signup and view all the answers

What occurs in males due to the absence of Tra protein?

<p>Exclusion of female doublesex exon</p> Signup and view all the answers

Match the following Delta isoforms to their localization:

<p>Delta A = Targeted to membrane Delta B = Targeted to nucleus Delta C = Targeted to cytoplasm</p> Signup and view all the answers

Exons 13 and 17 are never included in the splicing of calmodulin kinase.

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

What happens to transferrin receptor mRNA in high iron levels?

<p>It is degraded.</p> Signup and view all the answers

What effect does PTB binding to the 5' splice site have on U1 snRNP?

<p>It increases U1 snRNP and leads to activation.</p> Signup and view all the answers

Alternative splicing results in multiple mRNA isoforms from a single gene.

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

Which enzymes are responsible for the editing of adenosine to inosine in mRNA?

<p>ADAR enzymes</p> Signup and view all the answers

The localization of ASH1 mRNA to the budding tip of yeast cells is crucial for establishing _____ and asymmetric cell division.

<p>cell polarity</p> Signup and view all the answers

Which of the following proteins can convert cytidine (C) to uridine (U)?

<p>APOBEC1</p> Signup and view all the answers

Match the following components with their roles in RNA mechanisms:

<p>Doublesex = Key gene in sex determination in Drosophila U1 snRNP = Involved in splice site recognition and activation ADAR = Enzyme responsible for adenosine to inosine conversion APOBEC1 = Enzyme that converts cytidine to uridine</p> Signup and view all the answers

What is the role of the ratio of X chromosomes to autosomes in Drosophila?

<p>It triggers sex determination.</p> Signup and view all the answers

What is the effect of PTB binding to the 3' splice site on U2 snRNP?

<p>It reduces U2 snRNP and causes repression.</p> Signup and view all the answers

Study Notes

Gene Regulation Logic in Eukaryotes

  • Eukaryotic gene expression is spatially separated: transcription occurs in the nucleus while translation occurs in the cytoplasm.
  • This separation provides opportunities for extensive posttranscriptional regulation.
  • Eukaryotic gene structures are more complex with longer introns, requiring specific regulatory factors for accurate splicing.

Molecular Mechanisms: RNA Splicing, Editing, and Transport

  • RNA splicing is essential for the maturation of pre-mRNA, involving the removal of introns and joining of exons.
  • The spliceosome, a complex of small nuclear ribonucleoproteins (snRNPs) and associated proteins, carries out splicing.
  • Core cis-elements in splicing include 5' splice site, 3' splice site, branch point sequence, and polypyrimidine tract.
  • Trans-acting factors like spliceosomal snRNPs and regulatory RNA-binding proteins influence splicing outcomes.

Alternative Splicing

  • Allows a single gene to produce multiple protein isoforms, enhancing protein diversity and gene expression regulation.
  • Plays a critical role in developmental processes and differentiation through mRNA localization.

Sex Determination in Drosophila

  • Involves key genes: Sex-lethal (Sxl), Transformer (Tra), and Doublesex (Dsx).
  • The Sxl protein is activated by a specific X to autosome chromosome ratio, influencing sex-specific splicing.
  • In females, Sxl enhances inclusion of a female-specific exon; in males, it leads to a non-functional Sxl protein.
  • Tra proteins, regulated by Sxl, also influence Dsx splicing outcome leading to male or female-specific proteins.

RNA Binding Proteins and Splicing

  • RNA binding proteins like hnRNPs and tissue-specific regulators (e.g., RBFOX, NOVA) modulate splicing by interacting with splice sites.
  • PTB can inhibit splicing by outcompeting core factors and forming repressive complexes, depending on their binding position relative to exons.

Transport Mechanisms

  • mRNA localization is directed by specific sequences and RNA-binding proteins, impacting cellular differentiation.
  • Localization of ASH1 mRNA in yeast is vital for establishing cell polarity during asymmetric division.

Editing Mechanisms

  • Post-transcriptional editing modifies nucleotides in mRNAs, enhancing their coding potential.
  • ADAR enzymes convert adenosine to inosine, while APOBEC1 changes cytosine to uracil, which can lead to premature stop codons, e.g., apolipoprotein B difference in liver and intestine.

Diversity of RNA-Based Mechanisms

  • Alternative splicing contributes to significant protein diversity and regulates gene expression, affecting cellular outcomes.
  • Example of condition-specific mRNA stabilization includes the transferrin receptor, where iron levels influence mRNA degradation or stability based on IRE-binding protein interactions.

Experimental Approaches

  • Modern techniques to study posttranscriptional regulation include RNA sequencing, CRISPR gene editing, and high-throughput mass spectrometry to characterize mRNA modifications and splicing patterns.

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Related Documents

L4 Posttranscriptional Regulation of Eukaryotic Gene Expression PDF

Description

Explore the complexities of gene regulation in eukaryotes, focusing on the spatial separation of transcription and translation processes. This quiz covers crucial topics such as RNA splicing, editing, and the role of spliceosomes in gene expression. Test your understanding of the mechanisms that enable alternative splicing and its significance in protein diversity.

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