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Members of the sirtuin protein family link gene silencing and heterochromatin formation to NAD+-dependent histone deacetylation. Two papers now implicate O-acetyl-ADP-ribose, the metabolite produced by this reaction, as a small-molecule effector that binds to heterochromatic proteins.
The exosome is a complex composed of 3′→5′ exoribonucleases involved in RNA processing and degradation. The first high-resolution structure of the exosome core reveals a doughnut-like arrangement of six RNase PH–type subunits.
Translation termination, once thought to be the least complex of the steps in protein synthesis, is emerging as a process subject to considerable regulation. The prevalent mode for this regulation seems to be eRF-tweaking, the modulation of release factor activity by proteins involved in other gene expression pathways.
A recent study on the signaling conformation of the common receptor for the interleukin-6 family of cytokines, gp130, provides new insights into the activation mechanism of the 'tall' cytokine receptors.
RNA is present in a large complex containing the Rae1 protein, which promotes centrosome-independent spindle assembly in Xenopus laevis egg extracts. Because this activity does not require translation, it suggests a direct role for RNA during cell division.
Recent studies show that Hsp70 chaperones associate with ribosomes not only in yeast but also in humans. Differences seem to exist among species regarding the identities of Hsp70 homologs involved as well as the mechanisms of their ribosomal recruitment and activation.
A recent study reveals that the eukaryotic ribosomal protein L30 binds to the selenocysteine recoding RNA element and may function to tether the recoding machinery to the translating ribosome.
Work presented in this issue reveals the structure of a SNARE transmembrane domain and supports a model of exocytosis via hemifusion. Hemifusion may thus be a common intermediate in many, if not all, biological fusion reactions.
A new study shows that CtBP, a transcription corepressor, may mediate its effect by blocking histone acetylation, a mark of active transcription. This activity is modulated by NADH binding, thereby supporting a link between cellular metabolism and gene expression.
The Mre11 protein complex plays important roles in maintaining genome stability. Inter-molecular bridging by the Rad50 protein has now been shown to be critical to this complex's function.
A key to understanding bacterial pathogenicity is the mechanism by which water-soluble protein toxins assemble on cell membranes to form oligomeric bilayer-spanning pores. The recent reconstructions from cryo-electron micrographs of three-dimensional pore and prepore structures of the cholesterol-dependent toxin pneumolysin shed new light on the later steps of the assembly of large toxin pores.
Two recent reports describe potentially novel therapeutic approaches for treating tumors arising from mutations in the tumor suppressor genes BRCA1 and BRCA2. These studies support the idea that selective killing of tumor cells can be achieved by targeting a specific DNA repair pathway on which an individual tumor type has become dependent.
A noncoding regulatory RNA in Escherichia coli, SgrS, downregulates the message for the glucose transporter, limiting accumulation of toxic sugar phosphates. Now a new study finds that SgrS can work only when the target message is brought to the membrane by transmembrane coding regions.
A recent study suggests a novel role for the second extracellular loop of GPCRs: it may orchestrate a network of interactions that stabilize the inactive conformation of the receptor and control the on-off transition.
