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Bacterial type III secretion machines have adapted to carry out numerous functions, ranging from locomotion to protein delivery into nucleated cells. One of the most intriguing issues is the source of energy that fuels their activities. Despite recent advances, there are still many questions to be resolved.
Circadian rhythms are generated by cell-autonomous molecular clocks in organisms ranging from cyanobacteria to humans. Recent research on the mechanisms of molecular clocks call for a reflection on the cause and necessity of complexity in biological systems.
DNA damage activates signaling cascades driven by the ATM–ATR protein kinases, culminating in the recruitment of repair proteins to the damage site through poorly understood mechanisms. Now a flurry of papers reveals how ATM-dependent phosphorylation of mediator and chromatin-associated proteins at sites of double-strand breaks promotes ubiquitylation of local nucleosomes, thereby eliciting a powerful signal for recruitment of repair complexes to the damage site.
