Position of Eukaryotic Translation Initiation Factor eIF1A on the 40S Ribosomal Subunit Mapped by Directed Hydroxyl Radical Probing

The universally conserved eukaryotic initiation factor (eIF), eIF1A, plays multiple roles throughout initiation: it stimulates eIF2/GTP/Met-tRNA_i^{Met} attachment to 40S ribosomal subunits, scanning, start codon selection and subunit joining. Its bacterial ortholog IF1 consists of an oligonucleotide/oligosaccharide-binding (OB) domain, whereas eIF1A additionally contains a helical subdomain, N-terminal tail (NTT) and C-terminal tail (CTT). The NTT and CTT both enhance ribosomal recruitment of eIF2/GTP/Met-tRNA_i^{Met}, but have opposite effects on the stringency of start codon selection: the CTT increases, whereas the NTT decreases it. Here, we determined the position of eIF1A on the 40S subunit by directed hydroxyl radical cleavage. eIF1A's OB domain binds in the A site, similar to IF1, whereas the helical subdomain contacts the head, forming a bridge over the mRNA channel. The NTT and CTT both thread under Met-tRNA_i^{Met} reaching into the P-site. The NTT threads closer to the mRNA channel. In the proposed model, the NTT does not clash with either mRNA or Met-tRNA_i^{Met}, consistent with its suggested role in promoting the ‘closed’ conformation of ribosomal complexes upon start codon recognition. In contrast, eIF1A-CTT appears to interfere with the P-site tRNA-head interaction in the ‘closed’ complex and is likely ejected from the P-site upon start codon recognition

Position of eukaryotic translation initiation factor eIF1A on the 40S ribosomal subunit mapped by directed hydroxyl radical probing

The universally conserved eukaryotic initiation factor (eIF), eIF1A, plays multiple roles throughout initiation: it stimulates eIF2/GTP/Met-tRNAiMet attachment to 40S ribosomal subunits, scanning, start codon selection and subunit joining. Its bacterial ortholog IF1 consists of an oligonucleotide/oligosaccharide-binding (OB) domain, whereas eIF1A additionally contains a helical subdomain, N-terminal tail (NTT) and C-terminal tail (CTT). The NTT and CTT both enhance ribosomal recruitment of eIF2/GTP/Met-tRNAiMet, but have opposite effects on the stringency of start codon selection: the CTT increases, whereas the NTT decreases it. Here, we determined the position of eIF1A on the 40S subunit by directed hydroxyl radical cleavage. eIF1A's OB domain binds in the A site, similar to IF1, whereas the helical subdomain contacts the head, forming a bridge over the mRNA channel. The NTT and CTT both thread under Met-tRNAiMet reaching into the P-site. The NTT threads closer to the mRNA channel. In the proposed model, the NTT does not clash with either mRNA or Met-tRNAiMet, consistent with its suggested role in promoting the ‘closed’ conformation of ribosomal complexes upon start codon recognition. In contrast, eIF1A-CTT appears to interfere with the P-site tRNA-head interaction in the ‘closed’ complex and is likely ejected from the P-site upon start codon recognition

Position of eukaryotic translation initiation factor eIF1A on the 40S ribosomal subunit mapped by directed hydroxyl radical probing

The universally conserved eukaryotic initiation factor (eIF), eIF1A, plays multiple roles throughout initiation: it stimulates eIF2/GTP/Met-tRNAiMet attachment to 40S ribosomal subunits, scanning, start codon selection and subunit joining. Its bacterial ortholog IF1 consists of an oligonucleotide/oligosaccharide-binding (OB) domain, whereas eIF1A additionally contains a helical subdomain, N-terminal tail (NTT) and C-terminal tail (CTT). The NTT and CTT both enhance ribosomal recruitment of eIF2/GTP/Met-tRNAiMet, but have opposite effects on the stringency of start codon selection: the CTT increases, whereas the NTT decreases it. Here, we determined the position of eIF1A on the 40S subunit by directed hydroxyl radical cleavage. eIF1A's OB domain binds in the A site, similar to IF1, whereas the helical subdomain contacts the head, forming a bridge over the mRNA channel. The NTT and CTT both thread under Met-tRNAiMet reaching into the P-site. The NTT threads closer to the mRNA channel. In the proposed model, the NTT does not clash with either mRNA or Met-tRNAiMet, consistent with its suggested role in promoting the ‘closed’ conformation of ribosomal complexes upon start codon recognition. In contrast, eIF1A-CTT appears to interfere with the P-site tRNA-head interaction in the ‘closed’ complex and is likely ejected from the P-site upon start codon recognition

Derivation of pesticide aged sorption parameters from laboratory incubation data

The results of the incubation laboratory experiment showed that the decomposition of cyantraniliprole is bi-phasic and the rapid decomposition in the period after the application of the pesticide is accompanied by a subsequent slowdown of this process. The use of the biexponential equation increased the accuracy of the description of the dynamics of decomposition of cyantraniliprole, as evidenced by the static indices. The bi-exponential equation coefficients were used to calculate the parameters of non-equilibrium sorption. The obtained parameters served as input data for the PEARL model. Modelling the migration of cyantraniliprole with considering aged sorption, showed a significant decrease in the predicted concentrations of the pesticide in percolate

Influence of hydrodynamic dispersion and nonequilibrium sorption on the prediction of pesticide concentrations in lysimetric leachate

The article discusses issues related to the development of pesticide modeling in the environment and its use in order to regulate the circulation of pesticides. As the study of the literature and the author's experience in using mathematical models shows, the main problem and source of errors in modeling is the quality of the input data for the soil block of the model, as well as those characterizing the properties of the pesticide. Using the results of a carefully conducted lysimetric experiment to study the migration of cyantraniliprole outside the soil profile, as well as auxiliary studies, the influence of hydrodynamic dispersion on the behavior of the insecticide and the results of modeling is shown. The parameters of its non-equilibrium sorption by the soil were calculated according to the data of the laboratory experiment investigating the dynamics of decomposition of cyantraniliprole. The article confirms the need to take these processes into account when modeling the transport of pesticides

PP1 and PP2A phosphatases: cooperating partners in modulating retinoblastoma protein activation

The family of Retinoblastoma/pocket proteins is one of the master regulators of the eukaryotic cell cycle. It includes the retinoblastoma protein (Rb) and the related p107 and p130 proteins. The importance of the Rb pathway for homeostasis and tumor suppression is evident from the fact that inactivating mutations in Rb are frequently associated with many cancers. Retinoblastoma proteins regulate the cell cycle by controlling activity of the E2F family of transcription factors. The activity of Rb proteins themselves is modulated by their phosphorylation status at several Ser/Thr residues: phosphorylation by cyclin-dependent kinases (CDKs) inactivates Rb proteins and positively influences the transcription of genes necessary for cell cycle progression. While the mechanisms of CDK-mediated inactivation of Rb proteins are understood in great detail, our knowledge of the process that counteracts Rb phosphorylation is still quite limited. This review focuses on the Ser/Thr phosphatases that are responsible for dephosphorylation and thus activation of Rb proteins. Two major scenarios are considered: 1) when pocket proteins are dephosphorylated during regular cell cycle progression and 2) when rapid dephosphorylation is dictated by external stress or growth inhibitory conditions, such as oxidative stress, UV radiation or other DNA-damaging stimuli, and cell differentiation factors. It turns out that both PP1 and PP2A phosphatases can efficiently modulate pocket protein activity in a highly context-dependent manner and are tightly regulated by the presence of different regulatory subunits or interacting proteins.status: publishe

Study of cyantraniliprole sorption in soils of Russia

The sorption of the new insecticide cyantraniliprole was studied by the batch equilibrium method. The study of quantitative characteristics of cyantraniliprole sorption by the soils of different types showed that this process is well described by linear isotherms. According to obtained values of Koc, cyantraniliprole belongs to medium-mobility active substances of pesticides. The sorption value of cyantraniliprole was closely correlated with the content of organic carbon and clay. The regression equation of the dependence of Kd on soil organic carbon content was obtained

Migration of cyantraniliprole in fractured soils: calibration of pesticide leaching model by using experimental data

The phenomenon of preferential migration of substances can increase the risk of pesticides. In the first year of the experiment, in 7 days after application cyantraniliprole penetrated to a depth of 25 cm in agrosoddy-podzolic soil. In the next year on the 7th day after application the pesticide was detected at a depth of 15 cm. The pesticide migrated deeper than the unconfigured PERL model took into account. The calibration of the PERL model by using experimental data (soil experimental support) allowed to reduce the error of prediction. The obtained data can be used to create new standard soil and climate scenarios for pesticide leaching models

PP2A-Mediated Dephosphorylation of p107 Plays a Critical Role in Chondrocyte Cell Cycle Arrest by FGF

FGF signaling inhibits chondrocyte proliferation, a cell type-specific response that is the basis for several genetic skeletal disorders caused by activating FGFR mutations. This phenomenon requires the function of the p107 and p130 members of the Rb protein family, and p107 dephosphorylation is one of the earliest distinguishing events in FGF-induced growth arrest. To determine whether p107 dephoshorylation played a critical role in the chondrocyte response to FGF, we sought to counteract this process by overexpressing in RCS chondrocytes the cyclin D1/cdk4 kinase complex. CyclinD/cdk4-expressing RCS cells became resistant to FGF-induced p107 dephosphorylation and growth arrest, and maintained significantly high levels of cyclin E/cdk2 activity and of phosphorylated p130 at later times of FGF treatment. We explored the involvement of a phosphatase in p107 dephosphorylation. Expression of the SV40 small T-Ag, which inhibits the activity of the PP2A phosphatase, or knockdown of the expression of the PP2A catalytic subunit by RNA interference prevented p107 dephosphorylation and FGF-induced growth arrest of RCS cells. Furthermore, an association between p107 and PP2A was induced by FGF treatment. Our data show that p107 dephosphorylation is a key event in FGF-induced cell cycle arrest an