Beta-arrestin goes nuclear

Arrestins have important roles in the cytoplasm and at the plasma membrane, including the desensitization and internalization of G protein-coupled receptors (GPCRs). In this issue of Cell, Kang et al. (2005) provide evidence that beta-arrestin 1 moves to the nucleus in response to GPCR stimulation, where it regulates gene expression by facilitating histone acetylation at specific gene promoters.     

Ciliate biology: dynamin goes nuclear

Dynamin and dynamin-related proteins (DRPs) mediate an array of membrane fission processes. A Tetrahymena DRP has adopted a new role, assisting in nuclear differentiation, a finding that further highlights these proteins - and this ciliate - as biological innovators.     

Antiviral immunity. Viral restriction goes nuclear

Ustilago maydis Cmu1 is a virulence factor that can move through plant cells, redirecting plant metabolic pathways to favour fungal infection.     

Complementary miRNA pairs suggest a regulatory role for miRNA:miRNA duplexes

microRNAs (miRNAs) are 21-22-nucleotide noncoding RNAs that are widely believed to regulate complementary mRNA targets. However, due to the modest amount of pairing involved, only a few out of the hundreds of known animal miRNAs have thus far been connected to mRNA targets. Here, we considered the possibility that miRNAs might regulate non-mRNA targets, namely other miRNAs. To do so, we conducted a systematic assessment of the nearly complete catalogs of animal miRNAs for potential miRNA:miRNA complements. Our analysis uncovered several compelling examples that strongly suggest a function for miRNA duplexes, thus adding a potential layer of regulatory sophistication to the small RNA world. Interestingly, the most striking examples involve miRNAs complementary to members of the K-box family and Brd-box family, two classes of miRNAs previously implicated in regulation of Notch target genes. We emphasize that patterns of nucleotide constraint indicate that miRNA complementarity is not a simple consequence of miRNA:miRNA* complementarity; however, our findings do suggest that the potential regulatory consequences of the latter also deserve investigation.     

Rhizobium goes genomic

A report from the Rhizobium Functional Genomics Workshop, Sevilla, Spain, 15-16 September 2000.