Podcast
Questions and Answers
Which component is NOT considered part of the translation machinery?
Which component is NOT considered part of the translation machinery?
- Ribosomes
- Transfer RNAs
- Messenger RNAs
- DNA polymerase (correct)
The central dogma of molecular biology includes the processes of transcription and replication.
The central dogma of molecular biology includes the processes of transcription and replication.
False (B)
What is the primary function of tRNAs in translation?
What is the primary function of tRNAs in translation?
- To deliver amino acids and decode mRNA codons (correct)
- To degrade mRNA
- To provide energy for translation
- To form peptide bonds
What are the three main stages of translation?
What are the three main stages of translation?
The ribosome has only one binding site for tRNAs.
The ribosome has only one binding site for tRNAs.
Translation occurs in the ______ of the cell.
Translation occurs in the ______ of the cell.
Match the following terms with their descriptions:
Match the following terms with their descriptions:
What is the role of the ribosomal RNA in peptide bond formation?
What is the role of the ribosomal RNA in peptide bond formation?
The energy required to add the amino acid during translation primarily comes from _____ hydrolysis.
The energy required to add the amino acid during translation primarily comes from _____ hydrolysis.
What best defines the term 'translation' in molecular biology?
What best defines the term 'translation' in molecular biology?
Match the tRNA binding sites with their functions:
Match the tRNA binding sites with their functions:
How does the ribosome ensure translational fidelity?
How does the ribosome ensure translational fidelity?
What is the role of eIF2a phosphorylation in the cellular response?
What is the role of eIF2a phosphorylation in the cellular response?
The 5' methylated GTP cap is essential for regulating mRNA stability.
The 5' methylated GTP cap is essential for regulating mRNA stability.
What does GCN4 represent in yeast?
What does GCN4 represent in yeast?
The ___ tail affects mRNA stability and is composed of 100-200 adenosine residues.
The ___ tail affects mRNA stability and is composed of 100-200 adenosine residues.
Match the components of mRNA with their functions:
Match the components of mRNA with their functions:
What is one result of translational reprogramming during stress?
What is one result of translational reprogramming during stress?
The 3' UTR is responsible for promoting the binding of eIF4E.
The 3' UTR is responsible for promoting the binding of eIF4E.
What does uORF stand for and what is its significance in translation?
What does uORF stand for and what is its significance in translation?
What is the primary role of transfer RNAs (tRNAs) in translation?
What is the primary role of transfer RNAs (tRNAs) in translation?
The ribosomes move from the 3’ end to the 5’ end of the mRNA during translation.
The ribosomes move from the 3’ end to the 5’ end of the mRNA during translation.
What are the three key stages of translation?
What are the three key stages of translation?
The ribosomal _____ catalyzes the formation of peptide bonds between amino acids.
The ribosomal _____ catalyzes the formation of peptide bonds between amino acids.
Match the following structures with their functions in translation:
Match the following structures with their functions in translation:
What component of the ribosome is primarily responsible for positioning substrates for peptide bond formation?
What component of the ribosome is primarily responsible for positioning substrates for peptide bond formation?
The wobble hypothesis allows a single tRNA to recognize multiple codons.
The wobble hypothesis allows a single tRNA to recognize multiple codons.
What is the main purpose of the 5' methylated GTP cap on mRNA?
What is the main purpose of the 5' methylated GTP cap on mRNA?
The _____ position in the codon allows for non-Watson-Crick base pairing in the wobble hypothesis.
The _____ position in the codon allows for non-Watson-Crick base pairing in the wobble hypothesis.
Which factor is involved in scanning the mRNA for the start codon during translation initiation?
Which factor is involved in scanning the mRNA for the start codon during translation initiation?
What is the primary function of internal ribosome entry sites (IRES)?
What is the primary function of internal ribosome entry sites (IRES)?
Viruses do not utilize IRES for protein translation.
Viruses do not utilize IRES for protein translation.
What effect does phosphorylation of eEF1A and eEF1B have on translation elongation?
What effect does phosphorylation of eEF1A and eEF1B have on translation elongation?
The primary protein that is crucial for the recruitment of the 40S ribosomal subunit in cap-independent translation is encoded by the ______.
The primary protein that is crucial for the recruitment of the 40S ribosomal subunit in cap-independent translation is encoded by the ______.
Which process is crucial for viral replication?
Which process is crucial for viral replication?
Match the following factors to their roles in translation:
Match the following factors to their roles in translation:
Phosphorylation of eEF1A leads to a decrease in the rate of tRNA re-binding.
Phosphorylation of eEF1A leads to a decrease in the rate of tRNA re-binding.
What role does the integrated stress response play in viral infection?
What role does the integrated stress response play in viral infection?
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Study Notes
Overall Learning Outcomes
- Understand molecular mechanisms of translation: initiation, elongation, and termination.
- Describe regulation of translation stages at a molecular level with specific examples.
- Explain internal mRNA structures and their contribution to translation regulation.
Objectives-Part 1
- Review core concepts of translation.
- Identify primary components: Ribosomes, Transfer RNAs (tRNAs), and Messenger RNAs (mRNAs).
Central Dogma
- Central dogma explains the flow of genetic information: DNA → RNA → Protein.
- Reverse transcription can occur (e.g., in HIV).
Adaptor Hypothesis
- Each amino acid associates chemically with an enzyme, linking to a nucleic acid template.
Translation Process
- Ribosomes translate mRNA from the 5’ to 3’ end.
- Amino acids are delivered by tRNAs with complementary anticodon sequences.
- Peptide bonds form between amino acids at the ribosome.
The Ribosome
- Facilitates translation by catalyzing peptide bond formation.
- Comprised of two subunits: small (40S) "reads RNA" and large (60S) "joins amino acids."
Ribosomal Peptidyl Transferase
- Catalyzes peptide bond formation with enhanced activity through correct substrate positioning.
Mechanisms of Ribosome Activity
- Increases peptide bond formation rate by 10^7 times.
- 28S rRNA and specific ribosomal proteins ensure correct substrate positioning.
- Hydrogen bonding between tRNA and amino group is crucial for proton transfer during bond formation.
Transfer RNAs (tRNAs)
- Decode mRNA codons and deliver corresponding amino acids to ribosome.
- Possess a "cloverleaf structure" with amino acids attached at the 3’ end.
Wobble Hypothesis
- Allows non-Watson-Crick base pairing in the 3’ position of codons, enabling a single tRNA to recognize multiple codons.
- Reduces the number of required tRNA species.
Structure of a Typical mRNA
- Internal Ribosome Entry Site (IRES) allows cap-independent translation.
- 5' methylated GTP cap regulates export and stability, critical for initiation.
- 3’ Poly A tail (100-200 adenosines) enhances mRNA stability.
Key Steps in Translation Initiation
- 40S ribosomal subunit binds with eIFs to form the 43S complex.
- The complex targets the 5’ end of mRNA and scans for AUG stop codon.
- The 60S subunit associates, initiating translation upon AUG recognition.
Eukaryotic Initiation Factors (eIFs)
- eIF1/1A and eIF3 attach to 40S subunit facilitating assembly.
- eIF2/met-tRNA complex forms with GTP as energy source.
- eIF4E binds to mRNA cap, with eIF4G promoting circularization.
Translation Elongation
- tRNAs decode codons and deliver amino acids while forming peptide bonds.
- Ribosome contains three tRNA binding sites: A site (incoming tRNA), P site (growing peptide), and E site (exit for tRNAs).
Translation Fidelity
- The ribosome selects correct tRNA through a broader structural context.
- Error rate for tRNA selection is between 10^-3 and 10^-4.
Energy Requirements
- GTP hydrolysis provides energy for amino acid activation and peptide bond formation.
Translational Reprogramming in Stress
- Limits resource usage during stress and reprograms translation of specific transcripts for cell function improvement.
uORF Regulation of GCN4 Translation
- Involves ternary complex availability for scanning start codons, impacting translation efficiency.
IRES in Cap-Independent Translation
- IRES structures can recruit ribosomes independently of cap, engaging alternative initiation factors.
Viral Use of IRES
- Viruses utilize IRES for protein translation during stress, enhancing their replication efficiency.
Regulation of Translation Elongation
- Phosphorylation of eEF1A and eEF1B increases the rate of aminoacyl-tRNA recruitment, enhancing translation efficiency.
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