Related Experiment Video
Updated: Dec 28, 2025
06:49
Nonradioactive Assay to Measure Polynucleotide Phosphorylation of Small Nucleotide Substrates
Published on: May 8, 2020
5.1K
ELAC1 Repairs tRNAs Cleaved during Ribosome-Associated Quality Control
Matthew C J Yip1, Simonas Savickas2, Steven P Gygi1
1Department of Cell Biology, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA.
Cell Reports
|February 21, 2020
Summary
The enzyme ELAC1 is crucial for recycling tRNAs cleaved during ribosome-associated quality control (RQC). This process ensures proper protein synthesis by enabling the re-addition of essential nucleotides to damaged tRNAs.
Area of Science:
- Molecular Biology
- Cellular Biology
- Biochemistry
Background:
- Ribosome-associated quality control (RQC) manages stalled translation complexes.
- Cleavage of P-site tRNA by ANKZF1 releases incomplete polypeptides for degradation.
- Recycling cleaved tRNA requires re-adding 3'CCA nucleotides.
Purpose of the Study:
- To investigate the role of ELAC1 in the tRNA repair pathway following ANKZF1 cleavage.
- To understand the specialization of ELAC1 and ELAC2 in tRNA metabolism.
Main Methods:
- Biochemical assays to assess enzyme activity.
- Cellular studies to observe tRNA intermediates in ELAC1-deficient cells.
- Analysis of tRNA repair mechanisms in response to ribosome stalling.
Main Results:
- ELAC1 specifically removes the 2',3'-cyclic phosphate from ANKZF1-cleaved tRNAs.
- ELAC1 activity is essential for subsequent CCA re-addition by TRNT1.
- ELAC1 is optimized for tRNA recycling, distinct from ELAC2's role in tRNA biogenesis.
- Loss of ELAC1 leads to accumulation of unrepaired tRNA intermediates upon ribosome stalling.
Conclusions:
- ELAC1 is a key enzyme for the efficient recycling of tRNAs damaged during RQC.
- Vertebrates utilize a duplicated and specialized enzyme (ELAC1) for optimal tRNA repair and recycling.
- This specialization ensures cellular homeostasis by maintaining functional tRNAs for protein synthesis.
Related Concept Videos
02:07Improving Translational Accuracy
13.9K
Base complementarity between the three base pairs of mRNA codon and the tRNA anticodon is not a failsafe mechanism. Inaccuracies can range from a single mismatch to no correct base pairing at all. The free energy difference between the correct and nearly correct base pairs can be as small as 3 kcal/ mol. With complementarity being the only proofreading step, the estimated error frequency would be one wrong amino acid in every 100 amino acids incorporated. However, error frequencies observed in...
13.9K
01:29Protein Folding Quality Check in the RER
4.9K
ER is the primary site for the maturation and folding of soluble and transmembrane secretory proteins. The calnexin cycle is a specific chaperone system that folds and assesses the confirmation of N-glycosylated proteins before they can exit the ER lumen. The primary players of this quality check pipeline are the lectins, ER-resident chaperones, and a glucosyl transferase enzyme. In case the calnexin system in the lumen fails to salvage a misfolded protein, it is transported to the cytoplasm...
4.9K
01:32Export of Misfolded Proteins out of the ER
4.9K
After folding, the ER assesses the quality of secretory and membrane proteins. The correctly folded proteins are cleared by the calnexin cycle for transport to their final destination, while misfolded proteins are held back in the ER lumen. The ER chaperones attempt to unfold and refold the misfolded proteins but sometimes fail to achieve the correct native conformation. Such terminally misfolded proteins are then exported to the cytosol by ER-associated degradation or ERAD pathway for...
4.9K
01:37The Unfolded Protein Response
6.1K
The ER is the hub of protein synthesis in a cell. It has robust systems to quality control protein folding and also for degradation of terminally misfolded proteins. Under normal conditions, a small proportion of misfolded proteins that cannot be salvaged need to be transported to the cytoplasm by the ER-associated degradation or ERAD pathways. However, if the ERAD cannot handle the misfolded proteins, the cell activates the unfolded protein response or UPR to adjust the protein folding...
6.1K
01:20Cotranslational Protein Translocation
9.3K
Translocation of proteins across membranes is an ancient process that occurs even in bacteria and archaebacteria. In fact, the components of the translocation machinery are still conserved between prokaryotes and eukaryotes.
Sec61 channel partners for cotranslational translocation
During cotranslational translocation, the Sec61 channel partners with the signal recognition particle (SRP), the signal recognition particle receptor (SR), and the ribosomes to transport the nascent polypeptide chain...
Sec61 channel partners for cotranslational translocation
During cotranslational translocation, the Sec61 channel partners with the signal recognition particle (SRP), the signal recognition particle receptor (SR), and the ribosomes to transport the nascent polypeptide chain...
9.3K
01:27Post-translational Translocation of Proteins to the RER
7.3K
A sizable fraction of proteins destined for ER are first synthesized in the cell cytosol and then transported across the ER membrane–a process called post-translational translocation. Similar to cotranslationally translocated proteins, these proteins also use the Sec translocon complex to enter the ER lumen.
Targeting proteins to the ER
Hsp40 and Hsp70 chaperone molecules bind the translated proteins in the cytosol to prevent their folding. The chaperone binding helps to keep the signal...
Targeting proteins to the ER
Hsp40 and Hsp70 chaperone molecules bind the translated proteins in the cytosol to prevent their folding. The chaperone binding helps to keep the signal...
7.3K