Functional Significance of Branch Points in Mirtrons

MicroRNAs are a heterogeneous group of small regulatory RNAs generated by many pathways. Mirtrons (miR) are a class of microRNAs produced by splicing, and some mirtrons contain a 3’ tail located downstream from the self-complementary hairpin. During RNA splicing, a loop-like “lariat” intermediate structure is created when the 5’ end of the RNA is attached to an adenine called the branch point. The goal of this project is to uncover the contribution of branch point location to the processing of tailed mirtrons into functional gene regulators. This project approaches this issue from two directions. First, branch points were identified by generating all possible lariat signatures from specific intronic samples using LaSSO and aligning the signatures to a genome-wide Drosophila RNA-sequence library using Bowtie2. Second, a polymerase chain reaction (PCR) based branch point mapping strategy was used to experimentally isolate, mutate, and verify the branch point location of miR-1017. Additionally, a synthetic miR-1017 mutant was cloned without any adenine nucleotides in the 3’ tail. We examined the mutation’s effects on Drosophila S2 cells with transfection and Northern analysis. Northern analysis showed that the mutated branch point actually increased the production of mature mirtrons and removing the branch point abrogated expression entirely, indicating that mirtron maturation may be very dependent on branch point and its location

Pharmacokinetic-based failure of a detergent virucidal for severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) nasal infections: A preclinical study and randomized controlled trial

BACKGROUND: The nose is the portal for severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) infection, suggesting the nose as a target for topical antiviral therapies. The purpose of this study was to assess both the in vivo and in vitro efficacy of a detergent-based virucidal agent, Johnson and Johnson's Baby Shampoo (J&J), in SARS-CoV-2-infected subjects. METHODS: Subjects were randomized into three treatment groups: (1) twice daily nasal irrigation with J&J in hypertonic saline, (2) hypertonic saline alone, and (3) no intervention. Complementary in vitro experiments were performed in cultured human nasal epithelia. The primary outcome measure in the clinical trial was change in SARS-CoV-2 viral load over 21 days. Secondary outcomes included symptom scores and change in daily temperature. Outcome measures for in vitro studies included change in viral titers. RESULTS: Seventy-two subjects completed the clinical study (n = 24 per group). Despite demonstrated safety and robust efficacy in in vitro virucidal assays, J&J irrigations had no impact on viral titers or symptom scores in treated subjects relative to controls. Similar findings were observed administering J&J to infected cultured human airway epithelia using protocols mimicking the clinical trial regimen. Additional studies of cultured human nasal epithelia demonstrated that lack of efficacy reflected pharmacokinetic failure, with the most virucidal J&J detergent components rapidly absorbed from nasal surfaces. CONCLUSION: In this randomized clinical trial of subjects with SARS-CoV-2 infection, a topical detergent-based virucidal agent had no effect on viral load or symptom scores. Complementary in vitro studies confirmed a lack of efficacy, reflective of pharmacokinetic failure and rapid absorption from nasal surfaces