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Certain pathogens and bacterial toxins exhibit exquisite host specificity, the determinants of which often remain mysterious. A recent report shows that the human specificity of the pore-forming toxin intermedilysin (ILY), a member of the cholesterol-dependent cytolysins (CDCs), is due to its specific interaction with the human cluster of differentiation protein CD59.
Three recent reports identify the roles of specific ribonucleases necessary for efficient termination of transcription by RNA polymerase II. In one case, the primary cleavage event is carried out by a ribozyme encoded in the pre-mRNA itself.
Structural studies by the Ramakrishnan and Agris groups allow us to directly observe how the ribosome's decoding site accommodates non-Watson-Crick base pairs in the third position of the codon-anticodon triplet while maintaining the one-amino-acid-per-codon framework that is central to life.
Organisms such as yeast and humans are capable of both nonhomologous end joining (NHEJ) and homologous recombination (HR), but bacteria have typically been assumed to be capable only of HR. A recent study shows that mycobacteria accomplish NHEJ using just two proteins (homologs of the eukaryotic Ku and DNA ligase IV), whereas eukaryotes require many factors.
A combined structural and biochemical analysis of an essential stress protein in Escherichia coli provides the first detailed insights into a bacterial translation mechanism designed to cope with cold shock conditions.
Recent characterization of two distinct signals leading to IRF-3 activation in response to double-stranded RNA recognition by Toll-like receptor 3 provides new mechanistic information on the regulatory events that link the detection of viral invasion by the cell with the development of the antiviral response.
Retrovirus particles contain a dimeric form of their genomic RNA. A recent study suggests a mechanism that might underlie the selective incorporation of dimeric RNAs into assembling virus particles.
A new report provides evidence that the TFIIB-RNAPII interaction depends on the presence of additional factors and highlights the importance of structural characterization of the entire preinitiation complex.
The implication of arginine methylation in mRNA biogenesis from transcription to mRNA export has been documented by various groups, but the precise role of methylation in this process is still unknown. A recent study demonstrates that in Saccharomyces cerevisiae methylation modulates the interaction and recruitment of components of the RNA packaging and export machinery.
The human Kv1.1 potassium channel undergoes RNA editing in its pore domain. Editing replaces an isoleucine with a valine that results in rapid recovery from fast inactivation.
A second high-affinity binding site for the I-TevI homing endonuclease has been discovered. Surprisingly, the DNA sequence recognized is the protein's own operator; at this site, the endonuclease represses its own transcription instead of cleaving the DNA and inducing intron homing.
Ubiquitin-like proteins, including NEDD8, regulate a wide range of cellular processes and are mobilized by parallel biochemical pathways. A recent crystal structure explains how the NEDD8-specific E1 enzyme specifically recruits its cognate E2 enzyme by binding to a flexible N-terminal extension.
A recent study of adenylate kinase reveals that conformational dynamics in control product release and determine the rate-limiting step in the overall catalytic reaction.
