Development of Magoh protein-overexpressing HEK cells for optimized therapeutic protein production

In the pharmaceutical industry, the need for high levels of protein expression in mammalian cells has prompted the search for new strategies, including technologies to obtain cells with improved mechanisms that enhance its transcriptional activity, folding, or protein secretion. Chinese Hamster Ovary (CHO) cells are by far the most used host cell for therapeutic protein expression. However, these cells produce specific glycans that are not present in human cells and therefore potentially immunogenic. As a result, there is an increased interest in the use of human-derived cells for therapeutic protein production. For many decades, human embryonic kidney (HEK) cells were exclusively used for research. However, two products for therapeutic indication were recently approved in the United States. It was previously shown that tethered Magoh, an Exon-junction complex core component, to specific mRNA sequences, have had significant positive effects on mRNA translational efficiency. In this study, a HEK Magoh-overexpressing cell line and clones, designated here as HEK-MAGO, were developed for the first time. These cells exhibited improved characteristics in protein expression, reaching -two- to threefold increases in rhEPO protein production in comparison with the wild-type cells. Moreover, this effect was promoter independent highlighting the versatility of this expression platform.

De-immunized and Functional Therapeutic (DeFT) versions of a long lasting recombinant alpha interferon for antiviral therapy

Interferon α (IFN-α) exerts potent antiviral, immunomodulatory, and antiproliferative activity and have proven clinical utility in chronic hepatitis B and C virus infections. However, repeated IFN-α administration induces neutralizing antibodies (NAb) against the therapeutic in a significant number of patients. Associations between IFN-α immunogenicity and loss of efficacy have been described. So as to improve the in vivo biological efficacy of IFN-α, a long lasting hyperglycosylated protein (4N-IFN) derived from IFN-α2b wild type (WT-IFN) was developed. However, in silico analysis performed using established in silico methods revealed that 4N-IFN had more T cell epitopes than WT-IFN. In order to develop a safer and more efficient IFN therapy, we applied the DeFT (De-immunization of Functional Therapeutics) approach to producing functional, de-immunized versions of 4N-IFN. Using the OptiMatrix in silico tool in ISPRI, the 4N-IFN sequence was modified to reduce HLA binding potential of specific T cell epitopes. Following verification of predictions by HLA binding assays, eight modifications were selected and integrated in three variants: 4N-IFN(VAR1), (VAR2) and (VAR3). Two of the three variants (VAR1 and VAR3) retained anti-viral function and demonstrated reduced T-cell immunogenicity in terms of T-cell proliferation and Th1 and Th2 cytokine levels, when compared to controls (commercial NG-IFN (non-glycosylated), PEG-IFN, WT-IFN and 4N-IFN). It was previously demonstrated that N-glycosylation improved IFN-α pharmacokinetic properties. Here, we further reduce immunogenicity as measured in vitro using T cell assays and cytokine profiling by modifying the T cell epitope content of a protein (de-immunizing). Taking into consideration the present results and previously reported immunogenicity data for commercial IFN-α2b variants, 4N-IFN(VAR1) and 4N-IFN-4N(VAR3) appear to be promising candidates for improved IFN-α therapy of HCV and HBV.

Functional interconnections of Arabidopsis exon junction complex proteins and genes at multiple steps of gene expression

The exon junction complex (EJC) is deposited on mRNA after splicing and participates in several aspects of RNA metabolism, from intracellular transport to translation. In this work, the functional and molecular interactions of Arabidopsis homologues of Mago, Y14, and PYM, three EJC components that participate in intron-mediated enhancement of gene expression in animals, have been analysed. AtMago, AtY14, and AtPYM are encoded by single genes that show similar expression patterns and contain common regulatory elements, known as site II, that are required for expression. AtPYM and AtY14 are phosphorylated by plant extracts and this modification regulates complex formation between both proteins. In addition, overexpression of AtMago and AtY14 in plants produces an increase in AtPYM protein levels, while overexpression of AtPYM results in increased formation of a complex that contains the three proteins. The effect of AtMago and AtY14 on AtPYM expression is most likely to be due to intron-mediated enhacement of AtPYM expression, since the AtPYM gene contains a leader intron that is required for expression. Indeed, transient transformation asssays indicated that the three proteins are able to increase expression from reporter constructs that contain leader introns required for the expression of different genes. The results indicate that the plant homologues of Mago, Y14, and PYM are closely interconnected, not only through their function as EJC components but also at different steps of their own gene expression mechanisms, probably reflecting the importance of their interaction for the correct expression of plant genes.

Common sets of promoter elements determine the expression characteristics of three Arabidopsis genes encoding isoforms of mitochondrial cytochrome c oxidase subunit 6b

The promoters of the three Arabidopsis nuclear genes encoding mitochondrial cytochrome c oxidase subunit 6b (AtCOX6b) have similar expression patterns, with preferential expression in anthers and meristems, and are induced by sucrose and etiolation. Additionally, induction of AtCOX6b-1 by GA(3) and AtCOX6b-3 by 6-benzylaminopurine was observed. Site II elements (TGGGCC/T) present in the three promoters bind common nuclear proteins and are important for basal and induced expression. Induction by sucrose requires, in addition, the integrity of elements with the sequence TACTAA. The results imply the participation of common regulatory factors in the expression of the three Arabidopsis COX6b genes.

Transcriptional coordination of the biogenesis of the oxidative phosphorylation machinery in plants

Publicly available microarray experiments were used to analyze Arabidopsis thaliana genes whose expression is correlated with that of nuclear genes encoding components of the oxidative phosphorylation machinery (OxPhos genes). This analysis indicated the existence of coordination in the expression of genes encoding components of the five respiratory complexes. For these genes, preferential expression was observed in anthers and roots, especially in the elongation zone, while reduced or very low relative expression was evident in leaves and mature pollen grains. A global induction of OxPhos genes by carbohydrates, photo-destruction of chloroplasts, inhibition of cellulose synthesis, release from dormancy and germination, among other conditions, was also observed. Cluster analysis of the response of Arabidopsis genes to a set of 15 treatments allowed the identification of DNA motifs, known as site II, that are frequently present in the upstream regions of genes with responses like those of OxPhos genes. Mutagenic analysis of site II motifs in several genes encoding respiratory chain components showed that they actively participate in transcription of these genes. We conclude that an important number of nuclear genes encoding components of the five respiratory complexes show coordinated expression under various circumstances, and that site II elements and the putative proteins that interact with them are, together with as yet unidentified factors, important actors in this coordinated response.