RNA Processing and Regulation

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Questions and Answers

Which type of RNA degradation involves the cleavage of RNA internally?

Exoribonucleases

5'-3' exoribonucleases

3'-5' exoribonucleases

Endoribonucleases (correct)

What is the primary function of adenosine-to-inosine (A-to-I) editing?

Modulating RNA splicing

Generating RNA diversity

Preventing RNA toxicity

Regulating gene expression (correct)

Which protein is not a key component of the Nonsense-Mediated Decay (NMD) pathway?

Drosha (correct)

UPF3

SMG1

UPF1

What is the general term for quality control mechanisms that monitor and degrade aberrant RNA?

RNA surveillance Signup and view all the answers

What is the primary function of microRNAs (miRNAs) in regulating gene expression?

Binding to target mRNAs and preventing their translation Signup and view all the answers

What is the consequence of disrupting normal translation termination in cells?

Triggering of Nonsense-Mediated Decay (NMD) Signup and view all the answers

What is the primary reason for the degradation of incorrect RNA molecules?

To prevent incorrect RNA molecules from interfering with gene expression Signup and view all the answers

What is the function of TRAMP in the nucleus?

To degrade defective RNA molecules Signup and view all the answers

Which of the following is NOT a mechanism for controlling RNA quality?

Recruitment of transcription factors Signup and view all the answers

What is the effect of TRAMP-mediated degradation on RNA stability?

It decreases RNA stability Signup and view all the answers

What is the consequence of defective RNA molecules not being degraded?

They can interfere with gene expression Signup and view all the answers

What is the primary function of the TRAMP complex in RNA degradation?

To recognize and polyadenylate incorrect mRNAs for degradation Signup and view all the answers

What is the consequence of a nonsense-mediated mRNA decay event?

The production of a truncated protein Signup and view all the answers

Which type of RNA degradation occurs in the nucleus and targets incorrect rRNAs and tRNAs?

Exosome-mediated degradation Signup and view all the answers

What is the characteristic of mRNAs that are degraded through the Non-Stop Decay pathway?

They lack stop codons Signup and view all the answers

What is the primary mechanism by which the exosome complex degrades RNAs?

Through the action of exonucleases Signup and view all the answers

What is the main function of the TRAMP complex in the nucleus?

To degrade aberrant transcripts in the 3'-5' direction Signup and view all the answers

What is the consequence of a mutation that affects the polyadenylation of an mRNA?

The mRNA is degraded in the 3'-5' direction Signup and view all the answers

Which of the following is a characteristic of cryptic unstable transcripts (CUTs)?

They are degraded in the nucleus by the TRAMP complex Signup and view all the answers

What is the role of the Sen1 protein in the degradation of non-coding transcripts?

It facilitates the disassembly of the polymerase and attracts the TRAMP complex Signup and view all the answers

What is the structure of the exosome complex?

A toroidal structure with a small hole Signup and view all the answers

In the No-Go Decay pathway, what is the role of the complex induced by Ski7p?

To dissociate the ribosome and induce RNA degradation Signup and view all the answers

What is the primary consequence of not activating the ribosome quality control pathway?

Formation of high-density traffic jams of ribosomes Signup and view all the answers

What is the function of the RQC pathway?

To recognize and degrade defective ribosomes Signup and view all the answers

What is the common feature among the NMD, NSD, and NGD pathways?

Presence of a stalled ribosome, incorrect mRNA, and defective protein Signup and view all the answers

What happens to the ribosome and mRNA in the NGD pathway?

The ribosome is released, and the mRNA is degraded Signup and view all the answers

What is the likely result when an intron that has not been eliminated contains a stop codon?

The ribosome stalls and the NMD pathway is triggered Signup and view all the answers

What happens when a ribosome encounters a premature stop codon in an mRNA?

The ribosome stalls and the NMD pathway is triggered Signup and view all the answers

In organisms with intron-less genes, how is the distance between the premature stop codon and the polyA tail measured?

By the binding of UPF1 factors Signup and view all the answers

What is the consequence of a faulty NMD pathway in human diseases?

The production of a truncated protein leads to disease Signup and view all the answers

What is the purpose of designing drugs that allow ribosomes to continue translating mRNAs with premature stop codons?

To alleviate diseases caused by faulty NMD pathways Signup and view all the answers

Study Notes

RNA Degradation

Eukaryotic cells have multiple pathways for RNA degradation:
- Exoribonucleases (e.g. Xrn1, Xrn2) degrade RNA from the 5' end
- Endoribonucleases (e.g. RNase E) cleave RNA internally
- 3'-5' exoribonucleases (e.g. RRP44) degrade RNA from the 3' end
RNA degradation is crucial for:
- Regulating gene expression
- Removing aberrant or damaged RNA
- Preventing RNA toxicity

RNA Editing

Post-transcriptional modification of RNA that alters its sequence or structure
Two main types of RNA editing:
- Adenosine-to-inosine (A-to-I) editing: mediated by ADAR enzymes
- Cytidine-to-uridine (C-to-U) editing: mediated by APOBEC enzymes
RNA editing is involved in:
- Regulating gene expression
- Modulating RNA splicing
- Generating RNA diversity

Nonsense-Mediated Decay (NMD)

Surveillance pathway that detects and degrades aberrant mRNAs with premature stop codons
Key components:
- UPF1, UPF2, and UPF3 proteins
- SMG1, SMG5, and SMG6 proteins
NMD is triggered by:
- Presence of premature stop codons
- Disruption of normal translation termination
NMD is crucial for:
- Maintaining genomic integrity
- Preventing the production of truncated proteins

RNA Surveillance

General term for quality control mechanisms that monitor and degrade aberrant RNA
Includes:
- Nonsense-mediated decay (NMD)
- Non-stop decay (NSD)
- No-go decay (NGD)
- RNA exosome-mediated degradation
RNA surveillance is essential for:
- Maintaining RNA homeostasis
- Preventing RNA toxicity

MicroRNA Regulation

MicroRNAs (miRNAs) are small, non-coding RNAs that regulate gene expression
miRNAs bind to target mRNAs and prevent their translation
Key components:
- miRNA biogenesis pathway (Drosha, Dicer, Argonaute)
- miRNA-induced silencing complex (RISC)
miRNA regulation is involved in:
- Regulating gene expression
- Modulating cellular processes
- Maintaining cellular homeostasis

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Description

Test your knowledge of RNA processing and regulation, including RNA degradation, RNA editing, nonsense-mediated decay, RNA surveillance, and microRNA regulation. Learn about the different mechanisms and pathways involved in these processes.