The Saccharomyces cerevisiae RRM3 gene encodes a 5' to 3' DNA helicase. While replication of most of the yeast genome was not dependent upon Rrm3p, in its absence, replication forks paused and often broke at an estimated 1400 discrete sites, including tRNA genes, centromeres, inactive replication origins, and transcriptional silencers. These replication defects were associated with activation of the intra-S phase checkpoint. Activation of the checkpoint was critical for viability of rrm3Delta cells, especially at low temperatures. Each site whose replication was affected by Rrm3p is assembled into a nonnucleosomal protein-DNA complex. At tRNA genes and the silent mating type loci, disruption of these complexes eliminated dependence upon Rrm3p. These data indicate that the Rrm3p DNA helicase helps replication forks traverse protein-DNA complexes, naturally occurring impediments that are encountered in each S phase.

In diverse organisms, the Mre11 complex and phosphoinositide 3-kinase-related kinases (PIKKs), such as Tel1p and Mec1p from S. cerevisiae, are key mediators of DNA repair and DNA damage checkpoints that also function at telomeres. Here, we use chromatin immunoprecipitation (ChIP) to determine if Mre11p, Tel1p, or Mec1p affects telomere maintenance by promoting recruitment of telomerase subunits to S. cerevisiae telomeres. We find that recruitment of Est2p, the catalytic subunit of telomerase, and Est1p, a telomerase accessory protein, was severely reduced in mre11Delta and tel1Delta cells. In contrast, the levels of Est2p and Est1p binding in late S/G2 phase, the period in the cell cycle when yeast telomerase lengthens telomeres, were indistinguishable in wild-type (WT) and mec1Delta cells. These data argue that Mre11p and Tel1p affect telomere length by promoting telomerase recruitment to telomeres, whereas Mec1p has only a minor role in telomerase recruitment in a TEL1 cell.

Multiple pedagogical approaches, such as experimental experiences or computer-based activities, have been shown to increase student learning and engagement. We have developed a laboratory module that includes both a traditional "live" experimental component and a student-designed "virtual" computer simulation component. This laboratory employs the mating pathway of Saccharomyces cerevisiae (yeast) to demonstrate four fundamental cell and molecular biology concepts: cell signaling, cytoskeleton, cell cycle, and cell cycle checkpoints. In the live laboratory, students add mating pheromone to cultures, then measure changes in cell division and morphology characteristics of the S. cerevisiae mating response. We also developed a "virtual" complement to this laboratory. Using the principles of Design Thinking and Agile methodology, we collaborated with an undergraduate Computer Science course to generate two computer simulations which can support the live laboratory or provide a virtual laboratory experience. We assessed how both the live and virtual laboratories contributed to learning gains in analytical skills and course content. Students who performed the simulation alone or the simulation plus live lab demonstrated learning gains, with greater gains for the live lab, but students who performed neither lab did not. Attitudinal assessment demonstrated increased student engagement and self-efficacy after performing the live and virtual labs. © 2018 by The International Union of Biochemistry and Molecular Biology, 46:361-372, 2018.

Course-based undergraduate research experiences (CUREs) have been shown to increase student retention and learning in the biological sciences. Most CURES cover only one aspect of gene regulation, such as transcriptional control. Here we present a new inquiry-based lab that engages understanding of gene expression from multiple perspectives. Students carry out a forward genetic screen to identify regulators of the stationary phase master regulator RpoS in the model organism Escherichia coli and then use a series of reporter fusions to determine if the regulation is at the level of transcription or the post-transcription level. This easy-to-implement course has been run both as a 9-week long project and a condensed 5-6 week version in three different schools and types of courses. A majority of the genes found in the screen are novel, thus giving students the opportunity to contribute to original findings to the field. Assessments of this CURE show student gains in learning in many knowledge areas. In addition, attitudinal surveys suggest the students are enthusiastic about the screen and their learning about gene regulation. In summary, this lab would be an appropriate addition to an intermediate or advanced level Molecular Biology, Genetics, or Microbiology curriculum. © 2017 by The International Union of Biochemistry and Molecular Biology, 45(5):449-458, 2017.

Undergraduate biology laboratories emphasize hands‐on skills. Typically, descriptions of manual techniques are delivered via written instruction. Custom‐produced prelab instructional videos, which augment prelab instruction, have come into wider use in recent years. However, institutional and economic barriers can interfere with video production at all colleges and universities. In such cases, professionally produced laboratory instructional videos provide an attractive alternative. We hypothesized that students who watch short, professionally produced instructional videos before performing a laboratory would feel more confident and achieve greater learning gains than students whose prelab instruction was limited to handouts. For this proof of concept study, we investigated the value added when students watched a brief video, twice per lab, in an intermediate molecular biology course at a small, liberal arts university, and in a nonmajors biology course at a large, public research university. Both video and nonvideo comparison groups were administered a pre‐ and postlab exams. A postlab self‐efficacy survey was also administered to video groups. Our results reveal that in three out of the four laboratory classes, students who watched professional instruction videos performed significantly better in both pre‐ and postlab exams. For these students, we observed up to a two‐fold increase in test scores on scientific concepts and techniques. For all classes, most of the video group students reported that the video contributed to their confidence, comprehension of concepts, and understanding of how to conduct the lab. We conclude that professional instructional videos may address production barriers and have the potential to effectively enhance undergraduate science curricula and significantly improve students' performance.