Monoclonal antibodies that recognize plant cell wall glycans are used for high-resolution imaging, providing important information about the structure and function of cell wall polysaccharides. To characterize the binding epitopes of these powerful molecular probes a library of eleven plant arabinoxylan oligosaccharides was produced by automated solid-phase synthesis. Modular assembly of oligoarabinoxylans from few building blocks was enabled by adding (2-naphthyl)methyl (Nap) to the toolbox of orthogonal protecting groups for solid-phase synthesis. Conjugation-ready oligosaccharides were obtained and the binding specificities of xylan-directed antibodies were determined on microarrays.

Interactions between glycans and glycan binding proteins are essential for numerous processes in all kingdoms of life. Glycan microarrays are an excellent tool to examine protein–glycan interactions. Here, we present a microbe-focused glycan microarray platform based on oligosaccharides obtained by chemical synthesis. Glycans were generated by combining different carbohydrate synthesis approaches including automated glycan assembly, solution-phase synthesis, and chemoenzymatic methods. The current library of more than 300 glycans is as diverse as the mammalian glycan array from the Consortium for Functional Glycomics and, due to its microbial focus, highly complementary. This glycan platform is essential for the characterization of various classes of glycan binding proteins. Applications of this glycan array platform are highlighted by the characterization of innate immune receptors and bacterial virulence factors as well as the analysis of human humoral immunity to pathogenic glycans.

Summary LSH, a protein related to the SNF2 family of chromatin-remodelling ATPases, is essential for the correct establishment of DNA methylation levels and patterns in plants and mammalian cells. However, some of the phenotypes resulting from LSH deficiency cannot be explained easily by defects in DNA methylation. Here we show that LSH-deficient mouse and human fibroblasts show reduced viability after exposure to ionizing radiation and repair DNA double-strand breaks less efficiently than wild-type cells. A more detailed characterisation of this phenotype revealed that, in the absence of LSH, the histone variant H2AX is not efficiently phosphorylated in response to DNA damage. This results in impaired recruitment of MDC1 and 53BP1 proteins to DNA double-strand breaks and compromises phosphorylation of checkpoint kinase CHK2. Furthermore, we demonstrate that the ability of LSH to hydrolyse ATP is necessary for efficient phosphorylation of H2AX at DNA double-strand breaks and successful repair of DNA damage. Taken together, our data reveal a previously unsuspected role of LSH ATPase in the maintenance of genome stability in mammalian somatic cells, which is independent of its function in de novo DNA methylation during development.