NMR Model of the Entire Membrane-Interacting Region of the HIV-1 Fusion Protein and Its Perturbation of Membrane Morphology.

HIV-1 envelope glycoprotein (Env) is a transmembrane protein that mediates membrane fusion and viral entry. The membrane-interacting regions of the Env, including the membrane-proximal external region (MPER), the transmembrane domain (TMD), and the cytoplasmic tail (CT), not only are essential for fusion and Env incorporation but also can strongly influence the antigenicity of the Env. Previous studies have incrementally revealed the structures of the MPER, the TMD, and the KS-LLP2 regions of the CT. Here, we determined the NMR structure of the full-length CT using a protein fragment comprising the TMD and the CT in bicelles that mimic a lipid bilayer, and by integrating the new NMR data and those acquired previously on other gp41 fragments, we derived a model of the entire membrane-interacting region of the Env. The structure shows that the CT forms a large trimeric baseplate around the TMD trimer, and by residing in the headgroup region of the lipid bilayer, the baseplate causes severe exclusion of lipid in the cytoleaflet of the bilayer. All-atom molecular dynamics simulations showed that the overall structure of the MPER-TMD-CT can be stable in a viral membrane and that a concerted movement of the KS-LLP2 region compensates for the lipid exclusion in order to maintain both structure and membrane integrity. Our structural and simulation results provide a framework for future research to manipulate the membrane structure to modulate the antigenicity of the Env for vaccine development and for mutagenesis studies for investigating membrane fusion and Env interaction with the matrix proteins.

The NF-Y splicing signature controls hybrid EMT and ECM-related pathways to promote aggressiveness of colon cancer.

Aberrant splicing events are associated with colorectal cancer (CRC) and provide new opportunities for tumor diagnosis and treatment. The expression of the splice variants of NF-YA, the DNA binding subunit of the transcription factor NF-Y, is deregulated in multiple cancer types compared to healthy tissues. NF-YAs and NF-YAl isoforms differ in the transactivation domain, which may result in distinct transcriptional programs. In this study, we demonstrated that the NF-YAl transcript is higher in aggressive mesenchymal CRCs and predicts shorter patients' survival. In 2D and 3D conditions, CRC cells overexpressing NF-YAl (NF-YAlhigh) exhibit reduced cell proliferation, rapid single cell amoeboid-like migration, and form irregular spheroids with poor cell-to-cell adhesion. Compared to NF-YAshigh, NF-YAlhigh cells show changes in the transcription of genes involved in epithelial-mesenchymal transition, extracellular matrix and cell adhesion. NF-YAl and NF-YAs bind similarly to the promoter of the E-cadherin gene, but oppositely regulate its transcription. The increased metastatic potential of NF-YAlhigh cells in vivo was confirmed in zebrafish xenografts. These results suggest that the NF-YAl splice variant could be a new CRC prognostic factor and that splice-switching strategies may reduce metastatic CRC progression.

Gaseous Heptanethiol Removal by a Fe3+-Phenanthroline-Kaolinite Hybrid Material.

Kaolinite functionalized by the µ-oxo Fe3+-phenanthroline complex (Fe+3Phen) was selected to test its ability to efficiently remove and store gaseous heptanethiol (HPT). Spectroscopic techniques, elemental analysis, and thermal analysis coupled with evolved gas mass spectrometry were employed to characterize the material before and after the exposure to the gas and to define the adsorption process. The amount of HPT trapped by the functionalized kaolinite after 60 days is 0.10940 moles per 100 g of kaolinite which, considering the amount of adsorbed Fe+3Phen (0.00114 moles per 100 g of kaolinite), means a thiol/Fe3+Phen molar ratio of about 100:1, a value much higher than those found in the past for Fe+3Phen functionalized montmorillonite and sepiolite. In addition, the process was found to be efficient also beyond 60 days. This significant removal of the smelly gas was explained by considering a continuous catalytic activity of Fe3+ toward the oxidation of thiol to disulfide.