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Intertwining of DNA molecules frequently results in the formation of ‘ultrafine bridges’ between sister chromatids that need to be resolved during segregation of the chromatids into daughter cells. Although it has been established that these DNA bridges are coated by the helicase PICH, it has remained unknown how PICH assists in their resolution. A study now reveals that PICH directs the formation of positive DNA supercoiling in the presence of type I topoisomerases to promote the subsequent disentanglement of these DNA helices by type II topoisomerases. Remarkably, PICH might be able to reconfigure DNA topology by extruding loops of DNA while it moves along the double helix.
Chromatin organization in the nucleus plays an important role in cell-type-specific gene expression. A new study reports reconstruction of the 3D genome in single sensory neurons and provides insights into the regulation of genes encoding odorant receptors.
Bacteriophage-encoded anti-CRISPR (Acr) proteins were previously thought to inhibit CRISPR-mediated immunity by acting as physical barriers against the binding or cleavage of DNA. Two new studies report that recently discovered type V Acr proteins use enzymatic activities to shut down the Cas12a endonuclease, providing a multi-turnover ‘off switch’ for CRISPR-based immunity and technology.
Ubiquitin and ubiquitin-like proteins (UBLs) are essential regulators of a multitude of cellular processes, including autophagy. It is known that these proteins relay their effects by covalently modifying their substrate molecules. As an exception to this norm, Pang et al. report a novel phenomenon in which the UBL ATG12 interacts with its substrate ATG5 in a non-covalent fashion to promote autophagy in apicomplexan parasites and some yeasts.
Last year, several studies reported that proteins form biomolecular condensates at gene enhancers. Nair et al. now show that these condensates undergo physical changes over time, which affects their nuclear localization and the transcriptional output of their target genes.
Autophagy is a highly contextual modulator of tumorigenesis. A new study shows that autophagy can serve as a tumor suppressor to mediate cell death at replicative crisis.
Structural information on the respiratory supercomplex III2IV2 from budding yeast and from Mycobacterium smegmatis has become available, with cryo-EM work from four different groups.
A growing body of evidence suggests that cotranslational folding occurs from bacteria to mammalian cells, in particular for multi-domain proteins. In the assembly of yeast proteasomes, the initial interaction of Rpt1 and Rpt2 subunits has been found to take place on the translating ribosomes, coordinated by elongation pausing and involving the formation of Not1-containing compartments.
The Ninth International Conference on the Hsp90 Chaperone Machine concluded in October 2018, in Leysin, Switzerland. The program highlighted findings in various areas, including integrated insights into the molecular mechanism of Hsp90, cochaperones, and clients’ structure and function.
