Teaching biology students data exploration and visualization in a data-driven world.

As biologists accumulate or encounter increasingly large and complex data sets, our field creates the need for students to develop skills in data exploration and visualization. Many biology courses lack the time for students to develop the skills needed to parse complex datasets and visualize them appropriately. We developed a new upper-level undergraduate biology course to focused on data exploration and communication without requiring previous coding experience. We emphasized data visualization principles and best practices and taught students how to manage and visualize data via Tableau and R. We also explored scientific ethics, how to refute misinformation, and inequities that can occur in data collection and usage.

R Markdown as a dynamic interface for teaching: Modules from math and biology classrooms.

Advancing technologies, including interactive tools, are changing classroom pedagogy across academia. Here, we discuss the R Markdown interface, which allows for the creation of partial or complete interactive classroom modules for courses using the R programming language. R Markdown files mix sections of R code with formatted text, including LaTeX, which are rendered together to form complete reports and documents. These features allow instructors to create classroom modules that guide students through concepts, while providing areas for coding and text response by students. Students can also learn to create their own reports for more independent assignments. After presenting the features and uses of R Markdown to enhance teaching and learning, we present examples of materials from two courses. In a Computational Modeling course for math students, we used R Markdown to guide students through exploring mathematical models to understand the principle of herd immunity. In a Data Visualization and Communication course for biology students, we used R Markdown for teaching the fundamentals of R programming and graphing, and for students to learn to create reproducible data investigations. Through these examples, we demonstrate the benefits of R Markdown as a dynamic teaching and learning tool.

Identification of Rifampicin Resistance Mutations in Escherichia coli, Including an Unusual Deletion Mutation.

Rifampicin is an effective antibiotic against mycobacterial and other bacterial infections, but resistance readily emerges in laboratory and clinical settings. We screened Escherichia coli for rifampicin resistance and identified numerous mutations to the gene encoding the ß-chain of RNA polymerase (rpoB), including an unusual 9-nucleotide deletion mutation. Structural modeling of the deletion mutant indicates locations of potential steric clashes with rifampicin. Sequence conservation in the region near the deletion mutation suggests a similar mutation may also confer resistance during the treatment of tuberculosis.

A beacon in the cytoplasm: Tracking translation of single mRNAs.

Translation is carefully regulated to control protein levels and allow quick responses to changes in the environment. Certain questions about translation in vivo have been unattainable until now. In this issue, Pichon et al. (2016. J. Cell Biol http://dx.doi.org/10.1083/jcb.201605024) describe a new technique to allow real-time monitoring of translation on single mRNAs.

Coupling between the DEAD-box RNA helicases Ded1p and eIF4A.

Eukaryotic translation initiation involves two conserved DEAD-box RNA helicases, eIF4A and Ded1p. Here we show that S. cerevisiae eIF4A and Ded1p directly interact with each other and simultaneously with the scaffolding protein eIF4G. We delineate a comprehensive thermodynamic framework for the interactions between Ded1p, eIF4A, eIF4G, RNA and ATP, which indicates that eIF4A, with and without eIF4G, acts as a modulator for activity and substrate preferences of Ded1p, which is the RNA remodeling unit in all complexes. Our results reveal and characterize an unexpected interdependence between the two RNA helicases and eIF4G, and suggest that Ded1p is an integral part of eIF4F, the complex comprising eIF4G, eIF4A, and eIF4E.

U2 toggles iteratively between the stem IIa and stem IIc conformations to promote pre-mRNA splicing.

To ligate exons in pre-messenger RNA (pre-mRNA) splicing, the spliceosome must reposition the substrate after cleaving the 5' splice site. Because spliceosomal small nuclear RNAs (snRNAs) bind the substrate, snRNA structures may rearrange to reposition the substrate. However, such rearrangements have remained undefined. Although U2 stem IIc inhibits binding of U2 snRNP to pre-mRNA during assembly, we found that weakening U2 stem IIc suppressed a mutation in prp16, a DExD/H box ATPase that promotes splicing after 5' splice site cleavage. The prp16 mutation was also suppressed by mutations flanking stem IIc, suggesting that Prp16p facilitates a switch from stem IIc to the mutually exclusive U2 stem IIa, which activates binding of U2 to pre-mRNA during assembly. Providing evidence that stem IIa switches back to stem IIc before exon ligation, disrupting stem IIa suppressed 3' splice site mutations, and disrupting stem IIc impaired exon ligation. Disrupting stem IIc also exacerbated the 5' splice site cleavage defects of certain substrate mutations, suggesting a parallel role for stem IIc at both catalytic stages. We propose that U2, much like the ribosome, toggles between two conformations--a closed stem IIc conformation that promotes catalysis and an open stem IIa conformation that promotes substrate binding and release.

Multiple functions for the invariant AGC triad of U6 snRNA.

The invariant AGC triad of U6 snRNA plays an essential, unknown role in splicing. The triad has been implicated in base-pairing with residues in U2, U4, and U6. Through a genetic analysis in S. cerevisiae, we found that most AGC mutants are suppressed both by restoring pairing with U2, supporting the significance of U2/U6 helix Ib, and by destabilizing U2 stem I, indicating that this stem regulates helix Ib formation. Intriguingly, one of the helix Ib base pairs is required specifically for exon ligation, raising the possibility that the entirety of helix Ib is required only for exon ligation. We also found that U4 mutations that reduce complementarity in U4 stem I enhance U2-mediated suppression of an AGC mutant, suggesting that U4 stem I competes with the AGC-containing U4/U6 stem I. Implicating an additional, essential function for the triad, three triad mutants are refractory to suppression--even by simultaneous restoration of pairing with U2, U4, and U6. An absolute requirement for a purine at the central position of the triad parallels an equivalent requirement in a catalytically important AGC triad in group II introns, consistent with a role for the AGC triad of U6 in catalysis.