Protein synthesis in all cells begins with the ordered binding of the small ribosomal subunit to messenger RNA (mRNA) and transfer RNA (tRNA). In eukaryotes, translation initiation factor 3 (eIF3) is thought to play an essential role in this process by influencing mRNA and tRNA binding through indirect interactions on the backside of the 40S subunit. Here we show by directed hydroxyl radical probing that the human eIF3 subunit eIF3j binds to the aminoacyl (A) site and mRNA entry channel of the 40S subunit, placing eIF3j directly in the ribosomal decoding center. eIF3j also interacts with eIF1A and reduces 40S subunit affinity for mRNA. A high affinity for mRNA is restored upon recruitment of initiator tRNA, even though eIF3j remains in the mRNA-binding cleft in the presence of tRNA. These results suggest that eIF3j functions in part by regulating access of the mRNA-binding cleft in response to initiation factor binding.
Download full-text PDF |
Source |
|---|---|
| http://dx.doi.org/10.1016/j.molcel.2007.05.019 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
The 40S ribosomal subunit recycling complex modulates mitochondrial dynamics and endoplasmic reticulum - mitochondria tethering at mitochondrial fission/fusion hotspots.
Nat Commun
January 2025
Department of Biological Sciences, Dedman College of Humanities and Sciences, Southern Methodist University, Dallas, TX, 75275, USA.
The 40S ribosomal subunit recycling pathway is an integral link in the cellular quality control network, occurring after translational errors have been corrected by the ribosome-associated quality control (RQC) machinery. Despite our understanding of its role, the impact of translation quality control on cellular metabolism remains poorly understood. Here, we reveal a conserved role of the 40S ribosomal subunit recycling (USP10-G3BP1) complex in regulating mitochondrial dynamics and function.
View Article and Find Full Text PDFYeast Eukaryotic Initiation Factor 4B Remodels the MRNA Entry Site on the Small Ribosomal Subunit.
Biochemistry
January 2025
Department of Developmental Biology and Genetics, Indian Institute of Science, Bengaluru 560012, India.
Eukaryotic Initiation Factor 4 (eIF4) is a group of factors that activates mRNA for translation and recruit 43S preinitiation complex (PIC) to the mRNA 5' end, forming the 48S PIC. The eIF4 factors include mRNA 5' cap-binding protein eIF4E, ATP-dependent RNA helicase eIF4A, and scaffold protein eIF4G, which anchors eIF4A and eIF4E. Another eIF4 factor, eIF4B, stimulates the RNA helicase activity of eIF4A and facilitates mRNA recruitment.
View Article and Find Full Text PDF40S ribosomal subunits scan mRNA for the start codon by one-dimensional diffusion.
bioRxiv
January 2025
Department of Biochemistry & Biophysics at the School of Medicine and Dentistry & Center for RNA Biology, University of Rochester, Rochester, NY, USA.
During eukaryotic translation initiation, the small (40S) ribosomal subunit is recruited to the 5' cap and subsequently scans the 5' untranslated region (5' UTR) of mRNA in search of the start codon. The molecular mechanism of mRNA scanning remains unclear. Here, using GFP reporters in cells, we show that order-of-magnitude variations in the lengths of unstructured 5' UTRs have a modest effect on protein synthesis.
View Article and Find Full Text PDFCapturing eukaryotic ribosome dynamics in situ at high resolution.
Nat Struct Mol Biol
January 2025
Key Laboratory of Biomacromolecules (CAS), National Laboratory of Biomacromolecules, CAS Center for Excellence in Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
Many protein complexes are highly dynamic in cells; thus, characterizing their conformational changes in cells is crucial for unraveling their functions. Here, using cryo-electron microscopy, 451,700 ribosome particles from Saccharomyces cerevisiae cell lamellae were obtained to solve the 60S region to 2.9-Å resolution by in situ single-particle analysis.
View Article and Find Full Text PDFRibosome customization and functional diversification among P-stalk proteins regulate late poxvirus protein synthesis.
Cell Rep
January 2025
Department of Microbiology-Immunology, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA. Electronic address:
Growing evidence suggests that ribosomes selectively regulate translation of specific mRNA subsets. Here, quantitative proteomics and cryoelectron microscopy demonstrate that poxvirus infection does not alter ribosomal subunit protein (RP) composition but skews 40S rotation states and displaces the 40S head domain. Genetic knockout screens employing metabolic assays and a dual-reporter virus further identified two RPs that selectively regulate non-canonical translation of late poxvirus mRNAs, which contain unusual 5' poly(A) leaders: receptor of activated C kinase 1 (RACK1) and RPLP2.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!