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Eukaryotic cells have numerous non–membrane bound bodies whose functions are often unclear. On page 403 of this issue, Strzelecka and colleagues provide evidence that the ability to form Cajal bodies increases the rate of small nuclear ribonucleoprotein (snRNP) biogenesis and/or function. This supports the hypothesis that some cellular bodies form to increase the rates of assembly of multicomponent cellular machines.
Two recent papers break major new ground on the issues of NHEJ, backup pathways for NHEJ and how these relate to the chromosomal translocation process.
In this issue, a long-awaited report sheds new light on the strange performance of bacterial flagellar filaments. We now have high-resolution data on two different, 'switched' versions of the structure.
Synaptotagmins and SNAREs are known to couple Ca2+ sensing to membrane fusion during Ca2+-triggered exocytosis, but unraveling the mechanism of this coupling has proven extremely difficult. Two studies in this issue now provide crucial insights into the nature of synaptotagmin-SNARE interactions and reveal unsuspected similarities between synaptotagmins and viral fusion proteins.
Myotonic dystrophy is caused by expanded CTG repeats, and the expression of these repeats as RNA leads to the sequestration of the splicing factor muscleblind-like (MBNL1) to the CUG RNA. Two mouse models for myotonic dystrophy—mice expressing expanded CUG repeats and mice lacking functional MBNL1—now reveal ∼100 new mis-splicing events and a new class of aberrantly regulated mRNAs.
γ-secretase cleaves multiple substrates with essential roles from development to neurodegeneration, and its aberrant processing underlies human disorders including Alzheimer's disease (AD). Tian et al. now identify a domain in the β-amyloid precursor protein (APP) that inhibits γ-secretase activity and show that certain familial AD–linked APP mutations within this domain impair this inhibition, resulting in increased β-amyloid generation. The study thus reveals a novel mechanism whereby γ-secretase's activity is influenced by its own substrate.
An X-ray crystal structure of an organic anion transporter identifies it as an ion channel instead. Its similarity to an unrelated family of water channels raises evolutionary questions that have been recently bubbling up around membrane proteins.
