Riboswitches reside in the untranslated region of RNA and regulate genes involved in the biosynthesis of essential metabolites through binding of small molecules. Since their discovery at the beginning of this century, riboswitches have been regarded as potential antibacterial targets. Using fragment screening, high-throughput screening and rational ligand design guided by X-ray crystallography, lead compounds against various riboswitches have been identified. Here, we review the current status and suitability of the thiamine pyrophosphate (TPP), flavin mononucleotide (FMN), glmS, guanine, and other riboswitches as antibacterial targets and discuss them in a biological context. Further, we highlight challenges in riboswitch drug discovery and emphasis the need to develop riboswitch specific high-throughput screening methods.

Figure S1. (a-c) Specificity of the antibody was verified in sections of paraffin-embedded HEK cells transiently transfected with human b) and , respectively. The sections were subjected to immunofluorescence; (a) HEK cells transfected with human IL-20 stained with polyclonal rabbit anti-IL-20 and detected with Alexa 488 (green); (b) HEK cells transfected with human IL-20 and stained with a preimmune serum control from the rabbit in which the polyclonal rabbit anti-IL-20 was generated and detected with Alexa 488 (green); (c) HEK cells transfected with human IL-19 were stained with polyclonal rabbit anti-IL-20, and the nuclei were marked with Hoechst (blue). Stained for IL-20 (green); (d-g) localization of IL-20 protein in lesional psoriatic skin (LS). Paraffin-embedded punch biopsies from LS were subjected to immunofluorescence. (d) Stained for IL-20 (green); (e) same tissue as (d) stained with pre-immune-rabbit serum; (f) stained for IL-20 (green) and nuclear DNA (blue); (g) same tissue as (f), the anti-IL-20 has been pre-absorbed with antigen (IL-20), also stained for nuclear DNA (blue). Figure S2. Immunofluorescence stainings for IL-20 and double immunofluorescence stainings for IL-20 and selected CD markers in untreated lesional psoriatic skin. Figure S3. Effect of treatment with calcipotriol (10 patients, mild-to-moderate psoriasis) left panel, or cyclosporin A (10 patients, moderate-severe psoriasis) right panel, before (day 0) and after treatment for 14 and 28 days and compared with non-lesional skin also at day 0.Data S1. Experimental design. Table S1. Antibodies used for staining paraffinembedded punch biopsies. Abstract: Vitiligo is an acquired depigmentation disorder characterized by the loss of functional melanocytes from the epidermis. Two major theories of vitiligo pathogenesis include autoimmunity and oxidative stress-mediated toxicity in melanocytes. The present study aimed to evaluate both the hypotheses in vitiligo patients and to investigate their role in the disease onset and progression. Antimelanocyte antibody levels and lipid peroxidation (LPO) levels were evaluated in 427 patients and 440 controls; antithyroid peroxidase (TPO) antibody levels were estimated in 102 patients and 72 controls. Patients showed a significant increase in LPO and antimelanocyte antibody levels compared to controls. Antimelanocyte antibody and LPO levels were higher in active vitiligo compared to stable. Only 9.8% of patients showed the presence of anti-TPO antibodies in their circulation. Oxidative stress may be the initial triggering event to precipitate vitiligo in Gujarat population, which is exacerbated by contributing autoimmune factors together with oxidative stress.

The mycobacterial cell wall is a chemically complex array of molecular entities that dictate the pathogenesis of Mycobacterium tuberculosis. Biosynthesis and maintenance of this dynamic entity in mycobacterial physiology is still poorly understood. Here we demonstrate a requirement for M. tuberculosis MmpL11 in the maintenance of the cell wall architecture and stability in response to surface stress. In the presence of a detergent like Tyloxapol, a mmpL11 deletion mutant suffered from a severe growth attenuation as a result of altered membrane polarity, permeability and severe architectural damages. This mutant failed to tolerate permissible concentrations of cis-fatty acids suggesting its increased sensitivity to surface stress, evident as smaller colonies of the mutant outgrown from lipid rich macrophage cultures. Additionally, loss of MmpL11 led to an altered cellular fatty acid flux in the mutant: reduced incorporation into membrane cardiolipin was associated with an increased flux into the cellular triglyceride pool. This increase in storage lipids like triacyl glycerol (TAG) was associated with the altered metabolic state of higher dormancy-associated gene expression and decreased sensitivity to frontline TB drugs. This study provides a detailed mechanistic insight into the function of mmpL11 in stress adaptation of mycobacteria.

Rapid development within the fields of both fragment-based drug discovery (FBDD) and medicinal targeting of RNA provides possibilities for combining technologies and methods in novel ways. This review provides an overview of fragment-based screening (FBS) against RNA targets, including a discussion of the most recently used screening and hit validation methods such as NMR spectroscopy, X-ray crystallography, and virtual screening methods. A discussion of fragment library design based on research from small-molecule RNA binders provides an overview on both the currently limited guidelines within RNA-targeting fragment library design, and future possibilities. Finally, future perspectives are provided on screening and hit validation methods not yet used in combination with both fragment screening and RNA targets.

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