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Medical student use of lecture video (live-streaming and/or recorded) at a regional medical school campus that utilized distance educational technology to deliver first-year pre-clinical lecture content, was examined. Additionally, medical student video lecture use was compared to student performance on summative exams and final course grades. All learners achieved desired scientific competencies across all courses irrespective of their use of live-streamed or recorded video formats. Throughout the course of the year, medical student video use partitioned into one of two groups: students that only watched lecture in live-streaming format, and those that watched lecture only in recorded format. Interestingly, those medical students that predominantly preferred view lectures using the live-streaming format tended to achieve better summative test scores and final course grades compared to their peers that primarily utilized recorded video to obtain lecture content. Retrospectively, dimensions of personality scores were compared between the two groups (live-streaming viewers versus recorded viewers), and, of the five dimensions of personality, only the domain of conscientiousness differed between the two groups. This study suggests that, while medical students reached academic milestones utilizing either recorded or live-streamed video for obtaining lecture content during their first-year pre-clinical courses, there may be factors of learner personality influencing video use preference which in turn enhances student performance on summative exams and final course grades. These findings may have implications in curriculum design for other distance educational formats emphasizing classical scientific competencies in post-undergraduate study that rely on video delivery of lecture content.

Nonsense-mediated mRNA decay (NMD) performs two functions in eukaryotes, one in controlling the expression level of a substantial subset of genes and the other in RNA surveillance. In the vast majority of genes, nonsense mutations render the corresponding transcripts prone to surveillance and subject to rapid degradation by NMD. To examine whether some classes of nonsense transcripts escape surveillance, we asked whether NMD acts on mRNAs that undergo subcellular localization prior to translation. In Saccharomyces cerevisiae, wild-type ASH1 mRNA is one of several dozen transcripts that are exported from the mother-cell nucleus during mitotic anaphase, transported to the bud tip on actin cables, anchored at the bud tip, and translated. Although repressed during transport, translation is a prerequisite for NMD. We found that ash1 nonsense mutations affect transport and/or anchoring independently of NMD. The nonsense transcripts respond to NMD in a manner dependent on the position of the mutation. Maximal sensitivity to NMD occurs when transport and translational repression are simultaneously impaired. Overall, our results suggest a model in which ash1 mRNAs are insensitive to NMD while translation is repressed during transport but become sensitive once repression is relieved.

SIP1 gene encodes proteins that interact with the yeast Snf1p kinase involved in gene expression of elements participating in non-glucose carbon utilization. The abundance ratio of two distinct size classes of SIP1 transcripts exhibits a marked shift, depending on the carbon source in the growth medium, which favors the longer transcripts in glucose-grown cells. Steady-state levels of SIP1 are comparatively insensitive to changes in the relative abundance.

In Saccharomyces cerevisiae, Ash1p is a specific repressor of transcription that localizes exclusively to daughter cell nuclei through the asymmetric localization of ASH1 mRNA. This localization requires four cis-acting localization elements located in the ASH1 mRNA, five trans-acting factors, one of which is a myosin, and the actin cytoskeleton. The RNA-binding proteins that interact with these cis-elements remained to be identified. Starting with the 3′ most localization element of ASH1 mRNA in the three-hybrid assay, element E3, we isolated a clone corresponding to the C-terminus of She3p. We also found that She3p and She2p interact, and this interaction is essential for the binding of She3p with element E3 in vivo. Moreover, She2p was observed to bind the E3 RNA directly in vitro and each of the ASH1 cis-acting localization elements requires She2p for their localization function. By tethering a She3p-MS2 fusion protein to a reporter RNA containing MS2 binding sites, we observed that She2p is dispensable for She3p-MS2-dependent RNA localization. [ABSTRACT FROM AUTHOR]

Degradation of mRNA is a vital aspect of gene expression. In yeast, Dcp1p, Dcp2p, Lsm1-7p, and Xrn1p are required for mRNA decay and are localized within discrete cytoplasmic foci; in the May 2 issue of Science, Sheth and Parker provide compelling evidence that these foci represent sites for mRNA decay. [Copyright &y& Elsevier]

Nonsense-mediated mRNA decay (NMD) performs two functions in eukaryotes, one in controlling the expression level of a substantial subset of genes and the other in RNA surveillance. In the vast majority of genes, nonsense mutations render the corresponding transcripts prone to surveillance and subject to rapid degradation by NMD. To examine whether some classes of nonsense transcripts escape surveillance, we asked whether NMD acts on mRNAs that undergo subcellular localization prior to translation. In Saccharomyces cerevisiae, wild-type ASHI mRNA is one of several dozen transcripts that are exported from the mother-cell nucleus during mitotic anaphase, transported to the bud tip on actin cables, anchored at the bud tip, and translated. Although repressed during transport, translation is a prerequisite for NMD. We found that ashi nonsense mutations affect transport and/or anchoring independently of NMD. The nonsense transcripts respond to NMD in a manner dependent on the position of the mutation. Maximal sensitivity to NMD occurs when transport and translational repression are simultaneously impaired. Overall, our results suggest a model in which ashi mRNAs are insensitive to NMD while translation is repressed during transport but become sensitive once repression is relieved. [ABSTRACT FROM AUTHOR]

Pseudomonas aeruginosa delivers the toxin ExoU to eukaryotic cells via a type III secretion system. Intoxication with ExoU is associated with lung injury, bacterial dissemination and sepsis in animal model and human infections. To search for ExoU targets in a genetically tractable system, we used controlled expression of the toxin in Saccharomyces cerevisiae. ExoU was cytotoxic for yeast and caused a vacuolar fragmentation phenotype. Inhibitors of human calcium-independent (iPLA(2)) and cytosolic phospholipase A(2) (cPLA(2)) lipase activity reduce the cytotoxicity of ExoU. The catalytic domains of patatin, iPLA(2) and cPLA(2) align or are similar to ExoU sequences. Site-specific mutagenesis of predicted catalytic residues (ExoUS142A or ExoUD344A) eliminated toxicity. ExoU expression in yeast resulted in an accumulation of free palmitic acid, changes in the phospholipid profiles and reduction of radiolabeled neutral lipids. ExoUS142A and ExoUD344A expressed in yeast failed to release palmitic acid. Recombinant ExoU demonstrated lipase activity in vitro, but only in the presence of a yeast extract. From these data we conclude that ExoU is a lipase that requires activation or modification by eukaryotic factors.