mRNA distribution in skeletal muscle is associated with mRNA size

Skeletal muscle myofibers are large and elongated cells with multiple and evenly distributed nuclei. Nuclear distribution suggests that each nucleus influences a specific compartment within the myofiber and implies a functional role for nuclear positioning. Compartmentalization of specific mRNAs and proteins has been reported at the neuromuscular and myotendinous junctions, but mRNA distribution in non-specialized regions of the myofibers remains largely unexplored. We report that the bulk of mRNAs is enriched around the nucleus of origin and that this perinuclear accumulation depends on recently transcribed mRNAs. Surprisingly, mRNAs encoding large proteins – giant mRNAs – are spread throughout the cell and do not exhibit perinuclear accumulation. Furthermore, by expressing exogenous transcripts with different sizes we found that size contributes to mRNA spreading independently of mRNA sequence. Both these mRNA distribution patterns depend on microtubules and are independent of nuclear dispersion, mRNA expression level and stability, and the characteristics of the encoded protein. Thus, we propose that mRNA distribution in non-specialized regions of skeletal muscle is size selective to ensure cellular compartmentalization and simultaneous long-range distribution of giant mRNAs.

Intracellular Routing and Recognition of Lipid-Based mRNA Nanoparticles

Messenger RNA (mRNA) is being extensively used in gene therapy and vaccination due to its safety over DNA, in the following ways: its lack of integration risk, cytoplasmic expression, and transient expression compatible with fine regulations. However, clinical applications of mRNA are limited by its fast degradation by nucleases, and the activation of detrimental immune responses. Advances in mRNA applications, with the recent approval of COVID-19 vaccines, were fueled by optimization of the mRNA sequence and the development of mRNA delivery systems. Although delivery systems and mRNA sequence optimization have been abundantly reviewed, understanding of the intracellular processing of mRNA is mandatory to improve its applications. We will focus on lipid nanoparticles (LNPs) as they are the most advanced nanocarriers for the delivery of mRNA. Here, we will review how mRNA therapeutic potency can be affected by its interactions with cellular proteins and intracellular distribution.

Web crawling and mRNA sequencing analyze mechanisms of photobiomodulation

Background Photobiomodulation (PBM) is praised as a promising physical therapy, which has many advantages, such as noninvasive, painless. However, the mechanisms are not fully elucidated. Methods Using web crawling, mRNA sequence and bioinformatics analysis to select genes, functional annotation, and mechanisms. The expressions of inflammatory cytokines were measured using RT-qPCR. Results A total of 146 human genes and 57 pathways were identified about PBM. The 630nm LED-stimulated-MH7A cells were sequenced for further analyzing the mechanism of PBM. 2950 differentially expressed genes were identified, and the gene ontology term enrichment analysis and Kyoto encyclopedia of genes and genomes pathway analysis were performed to better understand functions and pathways. The 12 pathways were matched with the KEGG results of PBM and MH7A cells. A protein-protein interaction network was performed among genes in 12 pathways, and 10 outstanding proteins were identified. Importantly, the 9 genes were predicted with potential research value.And we also demonstrated that expression of inflammatory factors (IL-6, IL-1β, IL-8, and MMP-3) was reduced; meanwhile, the expression of anti-inflammatory factor IL-10 was promoted after 630nm LED. In conclusion, using web crawling, bioinformatics analysis, and mRNA sequence, we obtained 9 key genes and 10 important pathways about PBM. Importantly, we demonstrated the anti-inflammatory effect of 630nm LED red light by RT-qPCR.

Sequence and expression analysis of glucokinase mRNA from herbivorous Giant gourami (Osphronemus goramy)

Sari DN, Nasrullah H, Ekasari J, Suprayudi MA, Alimuddin A. 2021. Sequence and expression analysis of glucokinase mRNA from herbivorous Giant gourami (Osphronemus goramy). Biodiversitas 22: 741-750. Glucokinase (GCK) is one of the enzymes that play important roles in carbohydrate metabolism and high glucose homeostatic in fish. The information about the GCK mRNA sequence and its expression is limited in Giant gourami, one of the most important herbivorous aquaculture species in Indonesia. The present study aimed to characterize the GCK mRNA and analyze its mRNA expression and plasma glucose levels after high glucose injection in Giant gourami. We also compared its sequence variability among carnivorous and herbivorous fish. The GCK mRNA was identified using polymerase chain reaction (PCR) method from the fish liver. Its mRNA level was analyzed by real-time PCR (qPCR). Giant gourami GCK mRNA sequence was 2104 nucleotide long, encoding 478 amino acids, and shared high similarity with other fish. GCK was mainly expressed in the liver. The mRNA level of GCK was highly up-regulated after 6 hours of high glucose injection, in-line with the plasma glucose in the blood. There are no major differences observed in the GCK amino acid sequences among Giant gourami and other fish. The knowledge gained from this study could be used as a reference for further exploration of metabolic regulation in Giant gourami.

Adaptive evolution at mRNA editing sites in soft-bodied cephalopods

Background The bulk of variability in mRNA sequence arises due to mutation—change in DNA sequence which is heritable if it occurs in the germline. However, variation in mRNA can also be achieved by post-transcriptional modification including mRNA editing, changes in mRNA nucleotide sequence that mimic the effect of mutations. Such modifications are not inherited directly; however, as the processes affecting them are encoded in the genome, they have a heritable component, and therefore can be shaped by selection. In soft-bodied cephalopods, adenine-to-inosine RNA editing is very frequent, and much of it occurs at nonsynonymous sites, affecting the sequence of the encoded protein. Methods We study selection regimes at coleoid A-to-I editing sites, estimate the prevalence of positive selection, and analyze interdependencies between the editing level and contextual characteristics of editing site. Results Here, we show that mRNA editing of individual nonsynonymous sites in cephalopods originates in evolution through substitutions at regions adjacent to these sites. As such substitutions mimic the effect of the substitution at the edited site itself, we hypothesize that they are favored by selection if the inosine is selectively advantageous to adenine at the edited position. Consistent with this hypothesis, we show that edited adenines are more frequently substituted with guanine, an informational analog of inosine, in the course of evolution than their unedited counterparts, and for heavily edited adenines, these transitions are favored by positive selection. Our study shows that coleoid editing sites may enhance adaptation, which, together with recent observations on Drosophila and human editing sites, points at a general role of RNA editing in the molecular evolution of metazoans.

The Evolution of Imprinted microRNAs and Their RNA Targets

Mammalian genomes contain many imprinted microRNAs. When an imprinted miRNA targets an unimprinted mRNA their interaction may have different fitness consequences for the loci encoding the miRNA and mRNA. In one possible outcome, the mRNA sequence evolves to evade regulation by the miRNA by a simple change of target sequence. Such a response is unavailable if the targeted sequence is strongly constrained by other functions. In these cases, the mRNA evolves to accommodate regulation by the imprinted miRNA. These evolutionary dynamics are illustrated using the examples of the imprinted C19MC cluster of miRNAs in primates and C2MC cluster in mice that are paternally expressed in placentas. The 3′ UTR of PTEN, a gene with growth-related and metabolic functions, appears to be an important target of miRNAs from both clusters.

Adaptive evolution at mRNA editing sites in soft-bodied cephalopods

The bulk of variability in mRNA sequence arises due to mutation – change in DNA sequence which is heritable if it occurs in the germline. However, variation in mRNA can also be achieved by post-translational modification including mRNA editing, changes in mRNA nucleotide sequence that mimic the effect of mutations. Such modifications are not inherited directly; however, as the processes affecting them are encoded in the genome, they have a heritable component, and therefore can be shaped by selection. In soft-bodied cephalopods, adenine-to-inosine RNA editing is very frequent, and much of it occurs at nonsynonymous sites, affecting the sequence of the encoded protein. Here, we show that mRNA editing of individual nonsynonymous sites in cephalopods originates in evolution through substitutions at regions adjacent to these sites. As such substitutions mimic the effect of the substitution at the edited site itself, we hypothesize that they are favored by selection if the inosine is selectively advantageous to adenine at the edited position. Consistent with this hypothesis and with observations on Drosophila and human editing sites, we show that edited adenines are more frequently substituted with guanine, an informational analogue of inosine, in the course of evolution than their unedited counterparts, and for heavily edited adenines, these transitions are favored by positive selection. Thus, our study shows that coleoid editing sites may enhance adaptation, which, together with distinct evolutionary features of Drosophila and human editing sites, points at a general role of RNA editing in the molecular evolution of metazoans.

Thermodynamic control of −1 programmed ribosomal frameshifting

mRNA contexts containing a ‘slippery’ sequence and a downstream secondary structure element stall the progression of the ribosome along the mRNA and induce its movement into the −1 reading frame. In this study we build a thermodynamic model based on Bayesian statistics to explain how −1 programmed ribosome frameshifting can work. As training sets for the model, we measured frameshifting efficiencies on 64 dnaX mRNA sequence variants in vitro and also used 21 published in vivo efficiencies. With the obtained free-energy difference between mRNA-tRNA base pairs in the 0 and −1 frames, the frameshifting efficiency of a given sequence can be reproduced and predicted from the tRNA−mRNA base pairing in the two frames. Our results further explain how modifications in the tRNA anticodon modulate frameshifting and show how the ribosome tunes the strength of the base-pair interactions.

Structural insights into the mammalian late-stage initiation complexes

SUMMARYIn higher eukaryotes, the mRNA sequence in direct vicinity of the start codon, called the Kozak sequence (CRCCaugG, where R is a purine), is known to influence the rate of the initiation process. However, the molecular basis underlying its role remains poorly understood. Here, we present the cryo-electron microscopy (cryo-EM) structures of mammalian late-stage 48S initiation complexes (LS48S IC) in the presence of two different native mRNA sequences, β-globin and histone 4 (H4) at overall resolution of 3Å and 3.5Å, respectively. Our high-resolution structures unravel key interactions from the mRNA to eukaryotic initiation factors (eIF): 1A, 2, 3, 18S rRNA, and several 40S ribosomal proteins. In addition, we were able to study the structural role of ABCE1 in the formation of native 48S ICs. Our results reveal a comprehensive map of the ribosome/eIFs –mRNA and –tRNA interactions and suggest the impact of mRNA sequence on the structure of the LS48S IC.