Volume 11 Issue 2, February 2004

A new study refines the current understanding of the precise nature by which a glycoprotein folding sensor contributes to the accuracy of a post-translational checkpoint in eukaryotic gene expression.

ATP synthase research has reached a milestone as single-molecule techniques are used to examine the direction and stepping of the proton gradient–driven rotation, to determine the effect of forced rotation on ATP synthesis and to synchronously monitor rotation and nucleotide kinetics.

The mechanism of transmembrane β-barrel protein insertion into an intracellular membrane is essentially unknown. Two recent studies reveal that the process is protein-mediated and identify a protein complex that is involved.

Two recent structural studies on the GTPases of the bacterial signal recognition particle–receptor complex reveal how direct interactions between the two ribonucleotides in a shared GTP-binding cavity contribute to the assembly and the GTPase-activated disassembly of this targeting complex.

BLM, the helicase implicated in Bloom's syndrome, and its yeast counterpart Sgs1 function in complexes with a type I topoisomerase to resolve double Holliday junctions to form non-crossover products. These data provide a direct explanation for the highly elevated sister chromatid exchange frequency in Bloom's syndrome cells.

The degradation of eukaryotic mRNAs plays important roles in the modulation of gene expression, quality control of mRNA biogenesis and antiviral defenses. In the past five years, many of the enzymes involved in this process have been identified and mechanisms that modulate their activities have begun to be identified. In this review, we describe the enzymes of mRNA degradation and their properties. We highlight that there are a variety of enzymes with different specificities, suggesting that individual nucleases act on distinct subpopulations of transcripts within the cell. In several cases, translation factors that bind mRNA inhibit these nucleases. In addition, recent work has begun to identify distinct mRNP complexes that recruit the nucleases to transcripts through different mRNA-interacting proteins. These properties and complexes suggest multiple mechanisms by which mRNA degradation could be regulated.