Whether host DNA receptors have any capacity to distinguish self from nonself at the molecular level is an outstanding question in the innate immunity of mammals. Here, by using quantitative assays and electron microscopy, we show that cooperatively assembling into filaments on dsDNA may serve as an integral mechanism by which human IFN-inducible protein-16 (IFI16) engages foreign DNA. IFI16 is essential for defense against a number of different pathogens, and its aberrant activity is also implicated in several autoimmune disorders, such as Sjögren syndrome. IFI16 cooperatively binds dsDNA in a length-dependent manner and clusters into distinct protein filaments even in the presence of excess dsDNA. Consequently, the assembled IFI16·dsDNA oligomers are clearly different from the conventional noninteracting entities resembling beads on a string. The isolated DNA-binding domains of IFI16 engage dsDNA without forming filaments and with weak affinity, and it is the non-DNA-binding pyrin domain of IFI16 that drives the cooperative filament assembly. The surface residues on the pyrin domain that mediate the cooperative DNA binding are conserved, suggesting that related receptors use a common mechanism. These results suggest that IFI16 clusters into signaling foci in a switch-like manner and that it is capable of using the size of naked dsDNA as a molecular ruler to distinguish self from nonself.cooperative filament formation | inflammasome R ecognition of foreign intracellular DNA is a widely conserved defense mechanism by which the innate immune system of mammals detects and responds to invading pathogens (1, 2). Using such a universal molecule as a major danger signal for detecting pathogens must be regulated in a stringent yet efficient manner. However, only a few deciding factors are known for the host innate immune system to selectively engage foreign DNA (i.e., nonself-DNA) while minimizing interactions with self-DNA, which include the compartmentalization of mammalian cells and the size of foreign DNA. These features, however, only raise more questions than provide answers. For example, the footprints of intracellular DNA receptors usually fall below 20 bp, and yet a long foreign DNA fragment [e.g., poly(dA:dT); ≥1,000 bp] is required to induce a robust innate immune response even in a normally DNA-free environment like the cytoplasm (1, 2). On the other hand, foreign DNA-sensing pathways also exist in the host nucleus in which DNA receptors must not respond to abundant self-DNA to prevent spurious activities (1, 2). Indeed, one of the major unresolved questions in understanding the DNA-sensing pathways of mammals is whether the host intracellular DNA receptors have any capacity to distinguish self-from nonself-DNA at the molecular level (2).Human IFN inducible protein-16 (IFI16) is an intracellular DNA receptor of innate immunity that belongs to the family of absent-in-melanoma-2 (AIM2)-like receptors (ALRs) (1-4). IFI16 senses DNA from invading pathogens in both the nucleus and cytoplasm [e.g., vaccinia virus...

ABCG2 is a secretory efflux uric acid transporter of the kidney proximal tubule and gut that plays a key role in uric acid excretion. Genetic defect in ABCG2 leads to significant increases in serum urate levels (SUA) causing hyperuricemia and gout. A single common variant, Q141K, is responsible for the majority of ABCG2 associated gout risk. The Q141K mutation is a loss of function mutation associated with a severe reduction in protein abundance and transport function. Previously we hypothesized the Q141K mutation leads to instability in the nucleotide‐binding domain and here we present the specific molecular mechanism of the defect and a proof of concept of its correction using small molecules. We found using a ABCG2 structural model and targeted amino acid substitutions that the Q141K mutations leads to a localized disruption in packing that affects abundance and can be partially rescued with a secondary substitution at H155A. However the use of the signature motif suppressor mutation, G188E, provides full rescue of the Q141K abundance by stabilizing the NBD dimer sandwich, a finding consistent with a Q141K defect in NBD dimer formation. Finally we show that a small molecule, VRT‐325, known to bind directly to the NBD of ABC transporters can rescue both abundance and function of Q141K ABCG2.