Articles in 2008

A family of magnetic microstructures that should enable similar multiplexing capabilities in the magnetic resonance imaging (MRI) of biological samples have been developed. It is shown that careful control of the geometry of these magnetic particles yields well-defined spectral signatures in the radio-frequency spectrum used for MRI, effectively giving them characteristic 'colours' that can be readily distinguished from one another.

Acyl-homoserine lactone (AHL) quorum sensing allows population-dependent control of gene expression in numerous bacterial species. Many AHL quorum-sensing systems are known, all of which use fatty acid groups to provide AHL specificity. This paper reports the discovery that some bacteria make a non-fatty AHL by using enzymes related to the fatty AHL synthase pathway, thus greatly expanding the realm of signal possibilities.

The crystal structure of a ligand-free opsin at 2.9 Å resolution is reported; the entrance pathway for 11-cis-retinal and the exit pathway for all-trans-retinal are apparent.

Some of the TGF-β family of growth factors are responsible for contractility in vascular smooth muscle cells. This paper demonstrates that in response to ligand, TGF-β and bone morphogenetic proteins (BMP) promote the processing of a microRNA, miR-21, which regulates several genes involved in contractility. This occurs through a direct interaction of TGF-β and BMP with the DROSHA miRNA processing complex.

A report giving direct evidence of moonlets embedded in the bright core of Saturn's F ring, and showing that most of the F ring's morphology results from the continual gravitational and collisional effects of small satellites, often combined with the perturbing effect of Prometheus.

Malaria parasites must reproduce sexually to transmit to vectors, but very little is understood about their reproductive strategies. This paper details that malaria parasites adjust their sex ratios in response to unrelated conspecifics, as predicted by evolutionary theory.

Bacteroides fragilis is a member of the human intestinal microbiota. It is reported that a single molecule produced by this bacterium, polysaccharide A, can suppress the intestinal inflammatory response and thus protect from experimental colitis.

A genomic analysis of the reprogramming of murine fibroblasts and B lymphocytes was performed. It is shown that fully reprogrammed cells display gene expression and epigenetic states that are highly similar to embryonic stem cells. But in stable partially reprogrammed cell lines, there is reactivation of a distinct subset of stem cell-related genes and incomplete repression of lineage-specifying transcription factors.

Theriot and colleagues use fish keratocytes to study variations in cell shape that occur during motility. They report a model that quantitatively accounts for their experimental measurements and provides an explanation for the observed morphology of motile cells.

Supernovae are usually discovered through their 'delayed' light, which becomes visible some hours after the actual event. Now Soderberg et al. report the discovery of a supernova at the time of the explosion, marked by an extremely luminous X-ray outburst.

The 26S proteasome is a multisubunit complex that selectively degrades ubiquitin conjugated proteins. Two studies (this Article and the Letter Dikic doi:10.1038/nature06924) show that a known component of the proteasome, Rpn13, functions as a novel ubiquitin binding receptor, and structural studies reveal a novel mode of ubiquitin recognition. Rpn13 is also a receptor for a deubiquitinating enzyme, suggesting a linkage between ubiquitin chain recognition and disassembly.

DNA damage can be reversed by the homologous pairing of an undamaged DNA with a damaged DNA. Pavletich and colleagues report the structure of the E. coli strand-exchange protein, RecA, bound to DNA, offering new insight into the process by which homologous DNAs are paired.

Invertebrate rhodopsins are light-activated G-protein-coupled receptors, whose activity is coupled to Gq-type G-proteins. This paper reports the crystal structure of squid rhodopsin, at 2.5 Å, in which a putative G-protein-binding site is resolved.

Natural physical and biological systems change in regions of temperature increase. Such changes have occurred on all continents and in most oceans since at least 1970. This paper presents statistical evidence that these changes cannot be explained by natural climate variations alone, and concludes that anthropogenic climate change is affecting physical and biological systems globally and on some continents.

A study showing that homophilic E-cadherin complexes partition in very stable microdomains. Stability and lateral mobility of these microdomains depend on two distinct actin populations: small, stable actin patches stabilize homophilic E-cadherin clusters, whereas a rapidly turning over, contractile network constrains lateral diffusion by a tethering mechanism.

The PML tumour suppressor gene is involved in the development of some forms of leukaemia. New research has identified a role for PML in the quiescence and maintenance of haematopoietic stem cells and of leukaemia-initiating cells. PML can be targeted by arsenic trioxide and was shown to eliminate leukaemia-initiating cells, supporting its use as an anti-leukemia therapy.

HIV-1 reverse transcriptase (RT) is an important drug target. RT has two activities, DNA synthesis, and cleavage of a DNA–RNA hybrid. These activities require that RT bind to both DNA and RNA. Single-molecule technology is used to show that the enzyme binds to RNA and DNA in different orientations, and provide insight into how it can flip between these orientations and activities without dissociating from the substrate.