Biology subjects

Biziaev, N.

Publications and source records attributed to Biziaev, N..

4 recordsLinked to original sources

bioRxiv2026

Molecular mechanisms of PDCD4-mediated modulation of translation initiation and termination

PDCD4 is a tumor suppressor, known to affect protein translation by binding to a component of the eIF4F complex, eIF4A, and reducing its helicase activity, which is necessary for the 48S preinitiation complex formation and scanning of the 5 untranslated region of mRNA. PDCD4 has also been shown to interact with the ribosome and with translation initiation factors eIF4G, eIF4G2, eIF3, and PABP, all of which participate both in initiation and the closed-loop structure that couples initiation and termination. To investigate whether PDCD4 modulates initiation and termination through these interactions, we used a reconstituted mammalian translation system and pre-termination complexes purified from rabbit reticulocyte lysate. We found that PDCD4 suppresses early initiation events prior to eIF4F complex binding to the cap structure on mRNA. Moreover, inhibition of the helicase activity of eIF4A by PDCD4 is lost when the 40S subunit is present. Inhibition of 48S complex formation was also observed in the presence of the truncated eIF4G fragment p50 or the eIF4G2 isoform, both of which interact with eIF4A but lack the eIF4E-binding domain. PDCD4-mediated inhibition of initiation persisted regardless of the presence of PABP. During translation termination, PDCD4 did not affect eIF4A activity, indicating that its regulatory function toward eIF4A is stage-specific and restricted to initiation. Finally, we discovered that PDCD4 additively stimulates peptide release together with eIF3, eIF4G2, and PABP, but competes with eIF4F. Thus, PDCD4 employs a complex molecular mechanism targeting multiple translation factors to regulate different stages of protein synthesis.

molecular biology↗

bioRxiv2024

Eukaryotic initiation factors eIF4F and eIF4B promote translation termination upon closed-loop formation

Eukaryotic translation initiation factor eIF4F, comprising subunits eIF4G, eIF4E, and eIF4A, plays a pivotal role in the 48S preinitiation complex assembly and ribosomal scanning. Additionally, eIF4B enhances the helicase activity of eIF4A. eIF4F also interacts with PABP bound to the poly(A) tail of mRNA, thereby forming a closed-loop structure. PABP, in turn, interacts with eRF3, stimulating translation termination. Here, we employed a reconstituted mammalian system to directly demonstrate that eIF4F potently enhances translation termination. Specifically, eIF4A and eIF4B promote the loading of eRF1 into the A site of the ribosome, while eIF4G1 stimulates the GTPase activity of eRF3 and facilitates the dissociation of release factors following peptide release. We also identified MIF4G as the minimal domain required for this activity and show that eIF4G2/DAP5 can also promote termination. Our findings provide compelling evidence that the closed-loop mRNA structure facilitates translation termination, with PABP and eIF4F directly involved in this process.

molecular biology↗

bioRxiv2024

Peptidyl-tRNA hydrolysis rate influences the efficiency of nonsense-mediated mRNA decay

Nonsense variants underlie many genetic diseases. The phenotypic impact of nonsense variants is determined by nonsense-mediated mRNA decay (NMD), which degrades transcripts with premature termination codons (PTCs). Despite its clinical importance, the factors controlling transcript-specific and context-dependent variation in NMD activity remain poorly understood. Through analysis of human genetic datasets, we discovered that the amino acid preceding the PTC strongly influences NMD activity. Notably, glycine codons promote robust NMD efficiency and show striking enrichment before PTCs but depletion before normal termination codons (NTCs). This glycine-PTC enrichment is particularly pronounced in genes tolerant to loss-of-function variants, suggesting evolutionary selection or neutrality conferred by efficient elimination of truncated proteins from non-essential genes. Using biochemical assays and massively parallel reporter analysis, we demonstrated that the peptide release rate during translation termination varies substantially with the identity of the preceding amino acid and serves as the primary determinant of NMD activity. We propose a "window of opportunity" model where translation termination kinetics modulate NMD efficiency. By revealing how sequence context shapes NMD activity through translation termination dynamics, our findings provide a mechanistic framework for improved clinical interpretation of nonsense variants.

molecular biology↗

bioRxiv2020

Nsp1 of SARS-CoV-2 Stimulates Host Translation Termination

The Nsp1 protein of SARS-CoV-2 regulates the translation of host and viral mRNAs in cells. Nsp1 inhibits host translation initiation by occluding the entry channel of the 40S ribosome subunit. The structural study of SARS-CoV-2 Nsp1-ribosomal complexes reported post-termination 80S complex containing Nsp1 and the eRF1 and ABCE1 proteins. Considering the presence of Nsp1 in the post-termination 80S ribosomal complex simultaneously with eRF1, we hypothesized that Nsp1 may be involved in translation termination. Using a cell-free translation system and reconstituted in vitro translation system, we show that Nsp1 stimulates translation termination in the stop codon recognition stage at all three stop codons. This stimulation targets the release factor 1 (eRF1) and does not affect the release factor 3 (eRF3). The activity of Nsp1 in translation termination is provided by its N-terminal domain and the minimal required part of eRF1 is NM domain. We assume that biological meaning of Nsp1 activity in translation termination is binding with the 80S ribosomes translating host mRNAs and removal them from the pool of the active ribosomes.

molecular biology↗