U1 snRNA rewrites the "script".

Expression of eukaryotic mRNAs requires the collaboration of a host of RNA processing factors acting upon the transcript. Berg et al. describe how a pre-mRNA splicing factor modulates the activity of the polyadenylation machinery to regulate mRNA length, with important implications for isoform expression in activated neuronal and immune cells.

Dynamic histone acetylation is critical for cotranscriptional spliceosome assembly and spliceosomal rearrangements.

Assembly of the spliceosome onto pre-mRNA is a dynamic process involving the ordered exchange of snRNPs to form the catalytically active spliceosome. These ordered rearrangements have recently been shown to occur cotranscriptionally, while the RNA polymerase is still actively engaged with the chromatin template. We previously demonstrated that the histone acetyltransferase Gcn5 is required for U2 snRNP association with the branchpoint. Here we provide evidence that histone acetylation and deacetylation facilitate proper cotranscriptional association of spliceosomal snRNPs. As with GCN5, mutation or deletion of Gcn5-targeted histone H3 residues leads to synthetic lethality when combined with deletion of the genes encoding the U2 snRNP components Lea1 or Msl1. Gcn5 associates throughout intron-containing genes and, in the absence of the histone deacetylases Hos3 and Hos2, enhanced histone H3 acetylation is observed throughout the body of genes. Deletion of histone deacetylaces also results in persistent association of the U2 snRNP and a severe defect in the association of downstream factors. These studies show that cotranscriptional spliceosome rearrangements are driven by dynamic changes in the acetylation state of histones and provide a model whereby yeast spliceosome assembly is tightly coupled to histone modification.

Instructional Models for Course-Based Research Experience (CRE) Teaching.

The course-based research experience (CRE) with its documented educational benefits is increasingly being implemented in science, technology, engineering, and mathematics education. This article reports on a study that was done over a period of 3 years to explicate the instructional processes involved in teaching an undergraduate CRE. One hundred and two instructors from the established and large multi-institutional SEA-PHAGES program were surveyed for their understanding of the aims and practices of CRE teaching. This was followed by large-scale feedback sessions with the cohort of instructors at the annual SEA Faculty Meeting and subsequently with a small focus group of expert CRE instructors. Using a qualitative content analysis approach, the survey data were analyzed for the aims of inquiry instruction and pedagogical practices used to achieve these goals. The results characterize CRE inquiry teaching as involving three instructional models: 1) being a scientist and generating data; 2) teaching procedural knowledge; and 3) fostering project ownership. Each of these models is explicated and visualized in terms of the specific pedagogical practices and their relationships. The models present a complex picture of the ways in which CRE instruction is conducted on a daily basis and can inform instructors and institutions new to CRE teaching.

Genomic diversity of bacteriophages infecting Microbacterium spp.

The bacteriophage population is vast, dynamic, old, and genetically diverse. The genomics of phages that infect bacterial hosts in the phylum Actinobacteria show them to not only be diverse but also pervasively mosaic, and replete with genes of unknown function. To further explore this broad group of bacteriophages, we describe here the isolation and genomic characterization of 116 phages that infect Microbacterium spp. Most of the phages are lytic, and can be grouped into twelve clusters according to their overall relatedness; seven of the phages are singletons with no close relatives. Genome sizes vary from 17.3 kbp to 97.7 kbp, and their G+C% content ranges from 51.4% to 71.4%, compared to ~67% for their Microbacterium hosts. The phages were isolated on five different Microbacterium species, but typically do not efficiently infect strains beyond the one on which they were isolated. These Microbacterium phages contain many novel features, including very large viral genes (13.5 kbp) and unusual fusions of structural proteins, including a fusion of VIP2 toxin and a MuF-like protein into a single gene. These phages and their genetic components such as integration systems, recombineering tools, and phage-mediated delivery systems, will be useful resources for advancing Microbacterium genetics.

Introduction to cotranscriptional RNA splicing.

The discovery that many intron-containing genes can be cotranscriptionally spliced has led to an increased understanding of how splicing and transcription are intricately intertwined. Cotranscriptional splicing has been demonstrated in a number of different organisms and has been shown to play roles in coordinating both constitutive and alternative splicing. The nature of cotranscriptional splicing suggests that changes in transcription can dramatically affect splicing, and new evidence suggests that splicing can, in turn, influence transcription. In this chapter, we discuss the mechanisms and consequences of cotranscriptional splicing and introduce some of the tools used to measure this process.