Riboswitches are regulatory noncoding RNAs found in bacteria, fungi and plants, that modulate gene expressions through structural changes in response to ligand binding. Understanding how ligands interact with riboswitches in solution can shed light on the molecular mechanisms of this ancient regulators. Previous studies showed that riboswitches undergo global conformation changes in response to ligand binding to relay information. Here, we report conformation switching models of the recently discovered tetrahydrofolic acid-responsive second class of tetrahydrofolate (THF-II) riboswitches in response to ligand binding. Using a combination of selective 2′-hydroxyl acylation, analyzed by primer extension (SHAPE) assay, 3D modeling and small-angle X-ray scattering (SAXS), we found that the ligand specifically recognizes and reshapes the THF-II riboswitch loop regions, but does not affect the stability of the P3 helix. Our results show that the THF-II riboswitch undergoes only local conformation changes in response to ligand binding, rearranging the Loop1-P3-Loop2 region and rotating Loop1 from a ~120° angle to a ~75° angle. This distinct conformation changes suggest a unique regulatory mechanism of the THF-II riboswitch, previously unseen in other riboswitches. Our findings may contribute to the fields of RNA sensors and drug design.

We report here the synthesis, characterization, and antibacterial evaluation of transition metal complexes of Ni, Cu, Co, Mn, Zn, and Cd (6a–f), using a Schiff base ligand (5) derived from naproxen (an anti-inflammatory drug) and 5-bromosalicylaldehyde by a series of reactions. The ligand and the synthesized complexes were characterized by elemental analysis, UV-Visible, FTIR, and XRD techniques. The ligand 5 behaves as a bidentate donor and coordinates with metals in square planar or tetrahedral fashion. In order to evaluate its bioactivity profile, we screened the Schiff base ligand and its metal complexes (6a–f) against different species of bacteria and the complexes were found to exhibit significant antibacterial activity. The complexes showed more potency against Bacillus subtilis as compared to the other species. Moreover, we modeled these complexes’ binding affinity against COX1 protein using computational docking.

The success of messenger RNA (mRNA) vaccines in controlling COVID-19 has warranted further developments in new technology. Currently, their quality control process largely relies on low-resolution electrophoresis for detecting chain breaks. Here, we present an approach using multi-primer reverse transcription sequencing (MPRT-seq) to identify degradation fragments in mRNA products. Using this in-house-made mRNA containing two antigens and untranslated regions (UTRs), we analyzed the mRNA completeness and degradation pattern at a nucleotide resolution. We then analyzed the sensitive base sequence and its correlation with the secondary structure. Our MPRT-seq mapping shows that certain sequences on the 5′ of bulge–stem–loop structures can result in preferential chain breaks. Our results agree with commonly used capillary electrophoresis (CE) integrity analysis but at a much higher resolution, and can improve mRNA stability by providing information to remove sensitive structures or sequences in the mRNA sequence design.

Tandem SAM-II/SAM-V riboswitch belongs to a class of riboswitches found in the marine bacterium ‘Candidatus Pelagibacter ubique’. Previous studies have demonstrated that these riboswitches have the potential for digital modulation of gene expression at both the transcriptional and translational levels. In this study, we investigate the conformational changes in the tandem SAM-II/SAM-V riboswitch binding to S-adenosylmethionine (SAM) using selective 2′-hydroxyl acylation analyzed by the primer extension (SHAPE) assay, small-angle X-ray scattering (SAXS), and oligos depressing probing. Our findings reveal that the linker between SAM-II/SAM-V aptamers blocks the SAM response of the SAM-II domain. This result proposes a new mechanism for gene expression regulation, where the ligand-binding functions of tandem riboswitches can be selectively masked or released through a linker.