Measuring magnetic correlations in nanoparticle assemblies

We illustrate how to extract correlations between magnetic moments in assemblies of nanoparticles from, e. g., electron holography data providing the combined knowledge of particle size distribution, inter-particle distances, and magnitude and orientation of each magnetic moment within a nanoparticle superstructure, We show, based on simulated data, how to build a radial/angular pair distribution function f(r, theta) encoding the spatial and angular difference between every pair of magnetic moments. A scatter-plot of f(r, theta) reveals the degree of structural and magnetic order present, and hence provides a measure of the strength and range of magnetic correlations

UBQLN4 Represses Homologous Recombination and Is Overexpressed in Aggressive Tumors

Genomic instability can be a hallmark of both human genetic disease and cancer. We identify a deleterious UBQLN4 mutation in families with an autosomal recessive syndrome reminiscent of genome instability disorders. UBQLN4 deficiency leads to increased sensitivity to genotoxic stress and delayed DNA double-strand break (DSB) repair. The proteasomal shuttle factor UBQLN4 is phosphorylated by ATM and interacts with ubiquitylated MRE11 to mediate early steps of homologous recombination-mediated DSB repair (HRR). Loss of UBQLN4 leads to chromatin retention of MRE11, promoting non-physiological HRR activity in vitro and in vivo. Conversely, UBQLN4 overexpression represses HRR and favors non-homologous end joining. Moreover, we find UBQLN4 overexpressed in aggressive tumors. In line with an HRR defect in these tumors, UBQLN4 overexpression is associated with PARP1 inhibitor sensitivity. UBQLN4 therefore curtails HRR activity through removal of MRE11 from damaged chromatin and thus offers a therapeutic window for PARP1 inhibitor treatment in UBQLN4-overexpressing tumors