Peter Schattner

The tRNAscan-SE, snoscan and snoGPS web servers for the detection of tRNAs and snoRNAs

Transfer RNAs (tRNAs) and small nucleolar RNAs (snoRNAs) are two of the largest classes of non-protein-coding RNAs. Conventional gene finders that detect protein-coding genes do not find tRNA and snoRNA genes because they lack the codon structure and statistical signatures of protein-coding genes. Previously, we developed tRNAscan-SE, snoscan and snoGPS for the detection of tRNAs, methylation-guide snoRNAs and pseudouridylation-guide snoRNAs, respectively. tRNAscan-SE is routinely applied to completed genomes, resulting in the identification of thousands of tRNA genes. Snoscan has successfully detected methylation-guide snoRNAs in a variety of eukaryotes and archaea, and snoGPS has identified novel pseudouridylation-guide snoRNAs in yeast and mammals. Although these programs have been quite successful at RNA gene detection, their use has been limited by the need to install and configure the software packages on UNIX workstations. Here, we describe online implementations of these RNA detection tools that make these programs accessible to a wider range of research biologists. The tRNAscan-SE, snoscan and snoGPS servers are available at , and , respectively.

The principles of guiding by RNA: chimeric RNA–protein enzymes

The non-protein-coding transcriptional output of the cell is far greater than previously thought. Although the functions, if any, of the vast majority of these RNA transcripts remain elusive, out of those for which functions have already been established, most act as RNA guides for protein enzymes. Common features of these RNAs provide clues about the evolutionary constraints that led to the development of RNA-guided proteins and the specific biological environments in which target specificity and diversity are most crucial to the cell.

Regions of extreme synonymous codon selection in mammalian genes

Recently there has been increasing evidence that purifying selection occurs among synonymous codons in mammalian genes. This selection appears to be a consequence of either cis-regulatory motifs, such as exonic splicing enhancers (ESEs), or mRNA secondary structures, being superimposed on the coding sequence of the gene. We have developed a program to identify regions likely to be enriched for such motifs by searching for extended regions of extreme codon conservation between homologous genes of related species. Here we present the results of applying this approach to five mammalian species (human, chimpanzee, mouse, rat and dog). Even with very conservative selection criteria, we find over 200 regions of extreme codon conservation, ranging in length from 60 to 178 codons. The regions are often found within genes involved in DNA-binding, RNA-binding or zinc-ion-binding. They are highly depleted for synonymous single nucleotide polymorphisms (SNPs) but not for non-synonymous SNPs, further indicating that the observed codon conservation is being driven by negative selection. Forty-three percent of the regions overlap conserved alternative transcript isoforms and are enriched for known ESEs. Other regions are enriched for TpA dinucleotides and may contain conserved motifs/structures relating to mRNA stability and/or degradation. We anticipate that this tool will be useful for detecting regions enriched in other classes of coding-sequence motifs and structures as well.

Functionality and substrate specificity of human box H/ACA guide RNAs

A large number of box H/ACA RNAs have been identified in human cells, and have been predicted to account for nearly all pseudouridylation sites in human rRNAs. However, the function of these mammalian H/ACA RNAs in directing pseudouridylation has been verified experimentally in only two cases. In this study, we used three in vitro reconstitution systems, including yeast and mammalian systems, to test the function of seven H/ACA RNAs guiding16 pseudouridylation sites. Our results verified 12 of these sites; four predictions were incorrect. Further analyses indicated that three components, including the stability of the hairpin structure harboring the pseudouridylation pocket, the stability of guide sequence-target RNA base-pairing interaction, and the distance between the target uridine and the box H or ACA, were critical for the guide function, as changes in these components were sufficient to alter the functionality and specificity of the pseudouridylation pocket. The dynamic functional changes in response to changes in these three important components were further tested in vivo, and the results were completely consistent with the in vitro results. Finally, we compared our results with predictions made by two computer programs, as well as predictions made by human experts using visual inspection. We found that the predictions of one program (snoGPS) agreed with our experimental results with 100% sensitivity (12/12) and 75% specificity (3/4).

Genomics made easier: An introductory tutorial to genome datamining

Integrated genome databases--such as the UCSC, Ensembl and NCBI MapViewer databases--and their associated data querying and visualization interfaces (e.g. the genome browsers) have transformed the way that molecular biologists, geneticists and bioinformaticists analyze genomic data. Nevertheless, because of the complexity of these tools, many researchers take advantage of only a fraction of their capabilities. In this tutorial, using examples from medical genetics and alternative splicing, I describe some of the biological questions that can be addressed with these techniques. I also show why doing so typically is more effective than using alternative methods and indicate some of the resources available for learning more about the advanced capabilities of these powerful tools.

The Case for ‘Story-driven’ Biology Education

Can learning molecular biology and genetics be enjoyable? Of course it can. Biologists know their field is exciting and fascinating and that learning how cells and molecules shape the living world is extraordinarily interesting. But can students who are not already inclined towards science also be convinced that learning molecular biology is worthwhile? For example, students taking biology simply to satisfy an academic distribution requirement, or ones with previous negative school experiences that made them believe that science is boring and irrelevant? Is it possible to persuade such students that learning molecular biology and genetics can be fun? Of course, one might assert that the role of science educators is not to make learning fun, but to simply introduce concepts in a clear and coherent manner. However, I would claim that without motivating students, the amount of comprehension and retention will be limited. And there is evidence that introductory biology and genetics courses for nonmajors are far from ideal. For example, a 2008 study using a ‘genetic literacy test’ found that scores among non-science majors increased only 6% points, from 43 to 49%, after taking an introductory biology and genetics course (Bowling et al. 2008). Realising that increasing student motivation might improve student understanding and test scores, educators have begun to include content intended to better motivate students. Nevertheless, I believe that the steps taken to date have been limited and that alternate approaches, with greater emphasis on motivating and even entertaining students, would improve both student motivation and test performance.