Minigene-like inhibition of protein synthesis mediated by hungry codons near the start codon

Rare AGA or AGG codons close to the initiation codon inhibit protein synthesis by a tRNA-sequestering mechanism as toxic minigenes do. To further understand this mechanism, a parallel analysis of protein synthesis and peptidyl-tRNA accumulation was performed using both a set of lacZ constructs where AGAAGA codons were moved codon by codon from +2, +3 up to +7, +8 positions and a series of 3–8 codon minigenes containing AGAAGA codons before the stop codon. β-Galactosidase synthesis from the AGAAGA lacZ constructs (in a Pth defective in vitro system without exogenous tRNA) diminished as the AGAAGA codons were closer to AUG codon. Likewise, β-galactosidase expression from the reporter +7 AGA lacZ gene (plus tRNA, 0.25 μg/μl) waned as the AGAAGAUAA minigene shortened. Pth counteracted both the length-dependent minigene effect on the expression of β-galactosidase from the +7 AGA lacZ reporter gene and the positional effect from the AGAAGA lacZ constructs. The +2, +3 AGAAGA lacZ construct and the shortest +2, +3 AGAAGAUAA minigene accumulated the highest percentage of peptidyl-tRNAArg4. These observations lead us to propose that hungry codons at early positions, albeit with less strength, inhibit protein synthesis by a minigene-like mechanism involving accumulation of peptidyl-tRNA

Factors of the epidemiological triad that influence the persistence of human papilloma virus infection in women with systemic lupus erythematosus

We studied the epidemiologic triad-related factors influencing human papilloma virus (HPV) persistence in Mexican women with systemic lupus erythematosus (SLE). Patients aged ?18 years with SLE (American College of Rheumatology criteria), with and without HPV persistence, were selected. Groups were analyzed by (1) host: clinical disease characteristics; (2) agent: (I) infectious (prevalence, incidence, HPV genotype and co-infections (?2 HPV genotypes or mycoplasmas)), (II) chemical (contraceptives and immunosuppressive drugs) and (III) physical (vitamin D deficiency) and (3) environment. A total of 121 SLE patients were selected over a two-year period. (1) Host: mean age 45.8 years and disease duration 12.7 years. (2) Agent: (I) infectious. HPV infection prevalence in the second sample was 26.4%, high-risk HPV genotypes 21.5% and co-infections 7.4%. HPV infection incidence was 13.2%, persistence 13.2% and clearance 15.7%. (II) Chemical: use of oral hormonal contraceptives 5% and immunosuppressive treatment 97.5%. (III) Physical: Vitamin D levels were similar in both groups. (3) Environment: (I) natural. A total of 60.6% of patients were residents of Puebla City. (II) Social: The mean education level was 10.9. Poverty levels were: III degree 52.4%, IV degree 28% and II degree 17%. (III) Cultural behavioral: Onset of sexual life was 20.5 years, 10% had ?3 sexual partners and 51.2% were postmenopausal. In conclusion, no factor of the epidemiologic triad was associated with HPV infection prevalence. © The Author(s) 2018

lambda bar minigene-mediated inhibition of protein synthesis involves accumulation of peptidyl-tRNA and starvation for tRNA.

Expression of the bacteriophage lambda two-codon, AUG AUA, barI minigene (bar+) leads to the arrest of protein synthesis in cells defective in peptidyl-tRNA hydrolase (Pth). It has been hypothesized that translation of the bar+ transcript provokes premature release and accumulation of peptidyl-tRNA (p-tRNA). Inhibition of protein synthesis would then result from either starvation of sequestered tRNA or from toxicity of accumulated p-tRNA. To test this hypothesis and to investigate the cause of arrest, we used a coupled in vitro transcription-translation system primed with DNA containing bar+ and the beta-lactamase-encoding gene of the vector as a reporter. The results show that expression of bar+ minigene severely inhibits beta-lactamase polypeptide synthesis by Pth-defective extracts and partially inhibits synthesis by wild-type extracts. Fractions enriched for Pth, or a homogeneous preparation of Pth, prevented and reversed bar+-mediated inhibition. A mutant minigene, barA702, which changes the second codon AUA (Ile) to AAA (Lys), was also toxic for Pth-defective cells. Expression of barA702 inhibited in vitro polypeptide synthesis by Pth-defective extracts and, as with bar+, exogenous Pth prevented inhibition. Addition of pure tRNALys prevented inhibition by barA702 but not by bar+. Expression of bar+ and barA702 led to release and accumulation of p-tRNAIle and p-tRNALys respectively but bar+ also induced accumulation of p-tRNALys. Finally, bar+ stimulated association of methionine with ribosomes probably as fMet-tRNAfMet and the accumulation of methionine and isoleucine in solution as peptidyl-tRNA (p-tRNA). These results indicate that minigene-mediated inhibition of protein synthesis involves premature release of p-tRNA, misincorporation of amino acyl-tRNA, accumulation of p-tRNAs and possibly sequestration of tRNAs

A Novel Emergency Gas-to-Power System Based on an Efficient and Long-Lasting Solid-State Hydride Storage System: Modeling and Experimental Validation

In this paper, a gas-to-power (GtoP) system for power outages is digitally modeled and experimentally developed. The design includes a solid-state hydrogen storage system composed of TiFeMn as a hydride forming alloy (6.7 kg of alloy in five tanks) and an air-cooled fuel cell (maximum power: 1.6 kW). The hydrogen storage system is charged under room temperature and 40 bar of hydrogen pressure, reaching about 110 g of hydrogen capacity. In an emergency use case of the system, hydrogen is supplied to the fuel cell, and the waste heat coming from the exhaust air of the fuel cell is used for the endothermic dehydrogenation reaction of the metal hydride. This GtoP system demonstrates fast, stable, and reliable responses, providing from 149 W to 596 W under different constant as well as dynamic conditions. A comprehensive and novel simulation approach based on a network model is also applied. The developed model is validated under static and dynamic power load scenarios, demonstrating excellent agreement with the experimental results