An efficient NMR experiment for analyzing sugar-puckering in unlabeled DNA: application to the 26-kDa dead ringer-DNA complex

Small-molecule antagonism of the interaction of the RAGE cytoplasmic domain with DIAPH1 reduces diabetic complications in mice

The macro- and microvascular complications of type 1 and 2 diabetes lead to increased disease severity and mortality. The receptor for advanced glycation end products (RAGE) can bind AGEs and multiple proinflammatory ligands that accumulate in diabetic tissues. Preclinical studies indicate that RAGE antagonists have beneficial effects on numerous complications of diabetes. However, these antagonists target the extracellular domains of RAGE, which bind distinct RAGE ligands at diverse sites in the immunoglobulin-like variable domain and two constant domains. The cytoplasmic tail of RAGE (ctRAGE) binds to the formin, Diaphanous-1 (DIAPH1), and this interaction is important for RAGE signaling. To comprehensively capture the breadth of RAGE signaling, we developed small-molecule antagonists of ctRAGE-DIAPH1 interaction, termed RAGE229. We demonstrated that RAGE229 is effective in suppressing RAGE-DIAPH1 binding, Förster resonance energy transfer, and biological activities in cellular assays. Using solution nuclear magnetic resonance spectroscopy, we defined the molecular underpinnings of the interaction of RAGE229 with RAGE. Through in vivo experimentation, we showed that RAGE229 assuaged short- and long-term complications of diabetes in both male and female mice, without lowering blood glucose concentrations. Last, the treatment with RAGE229 reduced plasma concentrations of TNF-α, IL-6, and CCL2/JE-MCP1 in diabetic mice, in parallel with reduced pathological and functional indices of diabetes-like kidney disease. Targeting ctRAGE-DIAPH1 interaction with RAGE229 mitigated diabetic complications in rodents by attenuating inflammatory signaling.

Nuclear magnetic resonance analysis of protein-DNA interactions

Recent methodological and instrumental advances in solution-state nuclear magnetic resonance have opened up the way to investigating challenging problems in structural biology such as large macromolecular complexes. This review focuses on the experimental strategies currently employed to solve structures of protein-DNA complexes and to analyse their dynamics. It highlights how these approaches can help in understanding detailed molecular mechanisms of target recognition.

The structure of the Dead ringer-DNA complex reveals how AT-rich interaction domains (ARIDs) recognize DNA

The AT-rich interaction domain (ARID) is a DNA-binding module found in many eukaryotic transcription factors. Using NMR spectroscopy, we have determined the first ever three-dimensional structure of an ARID--DNA complex (mol. wt 25.7 kDa) formed by Dead ringer from Drosophila melanogaster. ARIDs recognize DNA through a novel mechanism involving major groove immobilization of a large loop that connects the helices of a non-canonical helix-turn-helix motif, and through a concomitant structural rearrangement that produces stabilizing contacts from a beta-hairpin. Dead ringer's preference for AT-rich DNA originates from three positions within the ARID fold that form energetically significant contacts to an adenine-thymine base step. Amino acids that dictate binding specificity are not highly conserved, suggesting that ARIDs will bind to a range of nucleotide sequences. Extended ARIDs, found in several sequence-specific transcription factors, are distinguished by the presence of a C-terminal helix that may increase their intrinsic affinity for DNA. The prevalence of serine amino acids at all specificity determining positions suggests that ARIDs within SWI/SNF-related complexes will interact with DNA non-sequence specifically.