Discovery of High Affinity Cyclic Peptide Ligands for Human ACE2 with SARS-CoV-2 Entry Inhibitory Activity.

The development of effective antiviral compounds is essential for mitigating the effects of the COVID-19 pandemic. Entry of SARS-CoV-2 virions into host cells is mediated by the interaction between the viral spike (S) protein and membrane-bound angiotensin-converting enzyme 2 (ACE2) on the surface of epithelial cells. Inhibition of this viral protein-host protein interaction is an attractive avenue for the development of antiviral molecules with numerous spike-binding molecules generated to date. Herein, we describe an alternative approach to inhibit the spike-ACE2 interaction by targeting the spike-binding interface of human ACE2 via mRNA display. Two consecutive display selections were performed to direct cyclic peptide ligand binding toward the spike binding interface of ACE2. Through this process, potent cyclic peptide binders of human ACE2 (with affinities in the picomolar to nanomolar range) were identified, two of which neutralized SARS-CoV-2 entry. This work demonstrates the potential of targeting ACE2 for the generation of anti-SARS-CoV-2 therapeutics as well as broad spectrum antivirals for the treatment of SARS-like betacoronavirus infection.

The H2A.Z and NuRD associated protein HMG20A controls early head and heart developmental transcription programs.

Specialized chromatin-binding proteins are required for DNA-based processes during development. We recently established PWWP2A as a direct histone variant H2A.Z interactor involved in mitosis and craniofacial development. Here, we identify the H2A.Z/PWWP2A-associated protein HMG20A as part of several chromatin-modifying complexes, including NuRD, and show that it localizes to distinct genomic regulatory regions. Hmg20a depletion causes severe head and heart developmental defects in Xenopus laevis. Our data indicate that craniofacial malformations are caused by defects in neural crest cell (NCC) migration and cartilage formation. These developmental failures are phenocopied in Hmg20a-depleted mESCs, which show inefficient differentiation into NCCs and cardiomyocytes (CM). Consequently, loss of HMG20A, which marks open promoters and enhancers, results in chromatin accessibility changes and a striking deregulation of transcription programs involved in epithelial-mesenchymal transition (EMT) and differentiation processes. Collectively, our findings implicate HMG20A as part of the H2A.Z/PWWP2A/NuRD-axis and reveal it as a key modulator of intricate developmental transcription programs that guide the differentiation of NCCs and CMs.

Anti-Proliferative Effects of Hesa-A on Human Cancer Cells with Different Metastatic Potential.

BACKGROUND: During the past few years, Hesa-A, a herbal-marine mixture, has been used to treat cancer as an alternative medicine in Iran. Based on a series of studies, it is speculated that Hesa-A possesses special cytotoxic effects on invasive tumors. To test this hypothesis, we investigated the selective anticancer effects of Hesa-A on several cancer cell lines with different metastatic potential. MATERIALS AND METHODS: Hesa-A was prepared in normal saline as a stock solution of 10 mg/ml and further diluted to final concentrations of 100 µg/ml, 200 µg/ ml, 300 µg/ml and 400 µg/ml. MTT-based cytotoxicity assays were performed with A549 (lung non small cancer), MCF-7 (breast adenocarcinoma), SKOV3 (ovarian cancer), and PC-3 (prostate adenocarcinoma) cells. RESULTS: All treated cancer cells showed significant (P<0.01) or very significant (P<0.0001) differences in comparison to negative control at almost all of the tested doses (100-400 µg/ml). At the lower dose (100 µg/ml), Hesa-A reduced cell viability to 66%, 45.3%, 35.5%, 33.2% in SKOV3, A549, PC-3 and MCF-7 cells, respectively. Moreover, at the highest dose (400 µg/ml), Hesa-A resulted in 88.5%, 86.6% , 84.9% and 79.3% growth inhibition in A549, MCF-7, PC-3 and SKOV3 cells, respectively. CONCLUSIONS: Hesa-A exert potent cytotoxic effects on different human cancer cells, especially those with a high metastatic potential.