RNA Processing Quiz

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Questions and Answers

What is the primary role of mRNA decay in cellular processes?

To promote transcriptional factors

To increase the lifespan of mRNA molecules

To regulate steady-state RNA levels (correct)

To enhance the stability of foreign RNA

Which of the following statements concerning eukaryotic mRNA decay is accurate?

Nonsense Mediated Decay is not part of eukaryotic mRNA decay.

It begins with exonucleolytic activity followed by de-adenylation.

3' UTR structure influences decay rate and efficiency. (correct)

The process requires no regulatory mechanisms.

What is the function of m6A modifications in RNA?

To solely enhance tRNA function

To prevent immune activation and provide quality control (correct)

To promote mRNA decay in all circumstances

To encourage immune activation against RNA viruses

What is a key step in the canonical RNA decay pathway in eukaryotes?

De-adenylation and de-capping Signup and view all the answers

What is the role of tRNA modifying enzymes related to m6A?

They may contribute to m6A abundance through spillover activity. Signup and view all the answers

Which RNA polymerase is responsible for transcribing ribosomal RNA in eukaryotic cells?

RNA Polymerase I Signup and view all the answers

Which of the following statements accurately describes post-transcriptional processing?

It includes modifications such as pseudouridine and polyA tails. Signup and view all the answers

What is a unique characteristic of rRNA processing in eukaryotes compared to the monocistronic rule?

rRNA is polycistronic, encoding multiple genes. Signup and view all the answers

What specific enzymes are responsible for modifying the 5' and 3' ends of tRNA during processing?

RNaseP and RNAseZ Signup and view all the answers

What is the consequence of nucleotide modifications like pseudouridylation in RNA?

Modulation of base-pairing and decoding. Signup and view all the answers

Which type of modification is specifically associated with the modification of the T loop in tRNA?

Adenosine deaminase activity Signup and view all the answers

Which characteristic of RNA Polymerase I is significant for its role in transcription?

It has a very strong promoter. Signup and view all the answers

Which of the following statements about the roles of snoRNAs in RNA processing is true?

snoRNAs guide modification of bases in rRNA. Signup and view all the answers

What is the role of the 7-methyl guanosine cap in mRNA processing?

It stabilizes mRNA and initiates translation. Signup and view all the answers

Which statement correctly describes the polyadenylation process?

Cleavage occurs after the CA sequence, facilitated by specific cleavage factors. Signup and view all the answers

Which function is NOT associated with the addition of the polyA tail to mRNA?

It facilitates splicing of introns. Signup and view all the answers

What is a key characteristic of histone mRNA compared to typical mRNA?

It has a short half-life regulated by the cell cycle. Signup and view all the answers

Which of the following statements about mRNA half-life is correct?

mRNA is known for its short half-life and high turnover. Signup and view all the answers

What is the primary result of the methylation of the 7-methyl guanosine cap?

It protects mRNA from degradation by exonucleases. Signup and view all the answers

What signals the addition of the polyA tail during mRNA processing?

AAUAAA sequence followed by a G-rich region. Signup and view all the answers

Which of the following describes a role of 2'OMe modifications in RNA?

They stabilize RNA and influence folding. Signup and view all the answers

Study Notes

RNA Processing

Eukaryotic RNA Polymerases:
- Pol I transcribes rRNA precursors (18S and 28S).
- Pol II transcribes mRNA, miRNAs, snRNAs, snoRNAs, and lincRNA.
- Pol III transcribes tRNA, 5S rRNA, other small RNAs, and gRNA.
- Post-transcriptional processing isn't encoded in the genome (e.g., pseudouridine, polyA tail).

Ribosomal RNA (rRNA) Processing

Prokaryotes: 16S, 23S, and 5S rRNA (tRNAs interspersed).
Eukaryotes: 18S, 5.8S, and 25S rRNA.
rRNA is polycistronic (one transcript encodes multiple genes) in eukaryotes, crucial for controlling rRNA dosage.
rRNA transcripts are initially large, processed through cleavage and modification in the nucleolus.
SnoRNAs guide these modifications.
Base pairing interactions with snoRNAs guide enzymes to modify rRNA bases (e.g., pseudouridine).

Transfer RNA (tRNA) Processing

tRNA is highly processed.
Anti-codon loop must be precisely formed.
RNaseP removes the 5' leader sequence.
RNaseZ removes the 3' end's UU.
A CCA-adding enzyme adds CCA to the 3' end.
Introns are excised by the TSEN complex.
Nucleotides are chemically modified (e.g., adenosine deaminase).
Modification is specific and crucial.

Messenger RNA (mRNA) Processing

mRNA processing includes capping, splicing, and polyadenylation.
Regulates mRNA export, stability, protein loading, and degradation.
*mRNA has a short half-life (hours).
*Pre-mRNA capping occurs co-transcriptionally (7-methyl guanosine cap):
- Removing 5' phosphate, adding GMP (5'-5'), methylating G.
- Functions for translation initiation (recognition by cap complex) and stabilizing mRNA (5'-->3' exonuclease protection).
Polyadenylation:
- Not encoded in DNA; signal is AAUAAA…CA followed by a U/GU-rich region.
- Poly A tail is crucial for mRNA stability, translation initiation, and export.

Splicing

Involves removal of introns and joining exons.
Organisms have differing intron content (yeasts vs. humans).
Introns can provide structural diversity and recombination opportunities.
Splicing is coupled with transcription.
Conserved splicing sequences (3' splice site + branch point seq + 5' splice site).
Spliceosome is a protein-directed ribozyme, containing snRNPs (each has a snRNA and many proteins).

RNA Editing

Modification of bases in RNA after transcription.
Editing can change the sequence and thus, the protein product.

RNA Decay

Post-transcriptionally regulated process.
Crucial for regulating mRNA levels and removing foreign RNA.
De-adenylation, de-capping, and exonucleolytic activity.
Several pathways regulate RNA decay. (nonsense-mediated decay (NMD), no-go decay(NGD), non-stop decay (NSD))

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Description

Test your knowledge on RNA processing in eukaryotes and prokaryotes, including the roles of different RNA polymerases and the intricacies of rRNA and tRNA processing. Explore how snoRNAs guide modifications and the significance of these processes in gene expression.