Regulation of translation

Summary

This transcript discusses the complex regulation of translation, the process by which mRNA is converted into proteins. It highlights two main categories: global regulation, where nutrient deprivation leads to a general reduction in protein synthesis, and gene-specific regulation, where particular mRNA transcripts are selectively regulated based on their sequence motifs. Key mechanisms, such as the stringent response in bacteria and riboswitches in bacteria and eukaryotes, illustrate how cells adapt to environmental changes. The importance of three-prime UTRs in eukaryotic mRNA regulation is also emphasized, showcasing the intricate controls that govern protein synthesis.

Takeaways

• 😀 Translation involves three main steps: initiation, elongation, and termination, essential for converting mRNA into polypeptides.
• 📉 Translation is regulated at multiple levels to ensure specific proteins are synthesized only when needed.
• 🔄 Global regulation of translation occurs in response to nutrient deprivation, with cells reducing protein synthesis during shortages.
• 🦠 In bacteria, uncharged tRNAs signal nutrient scarcity, leading to a stringent response that inhibits protein synthesis.
• 🌍 Eukaryotic cells respond to uncharged tRNAs by activating GCN2, which phosphorylates eIF2, resulting in reduced translation rates.
• 🔍 Gene-specific regulation involves specific mRNA sequences that modulate translation through binding by regulatory proteins or small molecules.
• 🔗 Riboswitches are RNA structures that change shape based on ligand presence, regulating ribosome access to mRNA binding sites.
• 💡 In bacteria, thiamine biosynthesis genes use riboswitches to control protein synthesis based on TPP levels.
• 📜 Eukaryotic regulation often occurs in the 3' UTR of mRNAs, where binding sites for regulatory proteins influence translation initiation.
• 🍼 Developmental regulation in embryos relies on post-transcriptional mechanisms, controlling the timing of protein synthesis using maternal mRNAs.

Q & A

What are the core steps of translation in mRNA transcripts?

The core steps of translation in mRNA transcripts include initiation, elongation, termination, and recycling.

How is translation regulated in cells?

Translation is regulated at multiple levels to ensure specific protein products are produced only when needed. This includes regulation at the transcription level and post-transcriptional regulation.

What is global regulation of translation?

Global regulation of translation occurs when a majority of mRNAs in the cell are translationally downregulated in response to external signals, such as nutrient deprivation.

How do bacterial cells respond to nutrient deprivation?

In bacterial cells, uncharged tRNAs signal nutrient deprivation. They bind to the ribosome's A site, blocking further protein synthesis and triggering the stringent response.

What role does Gcn2 play in eukaryotic cells' response to uncharged tRNAs?

In eukaryotic cells, uncharged tRNAs bind to Gcn2, activating it, which then phosphorylates eIF2. This phosphorylation reduces active eIF2 levels, leading to decreased rates of translation across most mRNAs.

What mechanisms do eukaryotic cells use to downregulate global translation?

Eukaryotic cells modulate the activities of the cap-binding protein eIF4E and its binding proteins. Phosphorylation of either eIF4E or 4E-BPs decreases their interaction, keeping active eIF4E levels high for efficient initiation.

What are gene-specific translation regulatory processes?

Gene-specific translation regulatory processes involve specific sequence motifs in an mRNA transcript that modulate its translation, often through the formation of functional structures or binding by regulatory molecules.

What is a riboswitch and how does it function?

A riboswitch is a specific RNA structure that can change shape in response to the binding of small molecules, affecting the accessibility of the ribosome binding site and thus regulating translation.

How does the three-prime UTR contribute to gene regulation in eukaryotes?

The three-prime UTR often contains binding sites for RNA-binding proteins, which influence translation initiation. These elements can affect the recruitment of translation initiation factors.

What is the significance of the Nanos mRNA in developmental regulation?

The Nanos mRNA contains a three-prime UTR motif that recruits proteins, which compete with normal translation initiation factors, thus regulating the timing of its translation during development.