Nuclear pore complexes (NPCs) gate the only conduits for nucleocytoplasmic transport in eukaryotes. Their gate is formed by nucleoporins containing large intrinsically disordered domains with multiple phenylalanine-glycine repeats (FG domains). In combination, these are hypothesized to form a structurally and chemically homogeneous network of random coils at the NPC center, which sorts macromolecules by size and hydrophobicity. Instead, we found that FG domains are structurally and chemically heterogeneous. They adopt distinct categories of intrinsically disordered structures in non-random distributions. Some adopt globular, collapsed coil configurations and are characterized by a low charge content. Others are highly charged and adopt more dynamic, extended coil conformations. Interestingly, several FG nucleoporins feature both types of structures in a bimodal distribution along their polypeptide chain. This distribution functionally correlates with the attractive or repulsive character of their interactions with collapsed coil FG domains displaying cohesion toward one another and extended coil FG domains displaying repulsion. Topologically, these bipartite FG domains may resemble sticky molten globules connected to the tip of relaxed or extended coils. Within the NPC, the crowding of FG nucleoporins and the segregation of their disordered structures based on their topology, dimensions, and cohesive character could force the FG domains to form a tubular gate structure or transporter at the NPC center featuring two

The Escherichia coil RNA polymerase oL-subunit binds through its carboxy-terminal domain (o~CTD) to a recognition element, the upstream (UP) element, in certain promoters. We used genetic and biochemical techniques to identify the residues in aCTD important for UP-element-dependent transcription and DNA binding. These residues occur in two regions of oLCTD, close to but distinct from, residues important for interactions with certain transcription activators. We used NMR spectroscopy to determine the secondary structure of ,vCTD. aCTD contains a nonstandard helix followed by four c~-helices. The two regions of ~CTD important for DNA binding correspond to the first a-helix and the loop between the third and fourth oL-helices. The o~CTD DNA-binding domain architecture is unlike any DNA-binding architecture identified to date, and we propose that aCTD has a novel mode of interaction with DNA. Our results suggest models for c~CTD-DNA and c~CTD-DNA-activator interactions during transcription initiation.

This study aims to uncover how specific bacteria and bile acids (BAs) contribute to steatosis induced by diet and farnesoid X receptor (FXR) deficiency in both genders. A control diet (CD) and Western diet (WD), which contains high fat and carbohydrate, were used to feed wild type (WT) and FXR knockout (KO) mice followed by phenotyping characterization as well as BA and microbiota profiling. Our data revealed that male WD-fed FXR KO mice had the most severe steatosis and highest hepatic and serum lipids as well as insulin resistance among the eight studied groups. Gender differences in WD-induced steatosis, insulin sensitivity, and predicted microbiota functions were all FXR-dependent. FXR deficiency enriched Desulfovibrionaceae, Deferribacteraceae, and Helicobacteraceae, which were accompanied by increased hepatic taurine-conjugated cholic acid and β-muricholic acid as well as hepatic and serum lipids. Additionally, distinct microbiota profiles were found in WD-fed WT mice harboring simple steatosis and CD-fed FXR KO mice, in which the steatosis had a potential to develop into liver cancer. Together, the presented data revealed FXR-dependent concomitant relationships between gut microbiota, BAs, and metabolic diseases in both genders. Gender differences in BAs and microbiota may account for gender dissimilarity in metabolism and metabolic diseases.