RESUMO
The binding of SARS-CoV-2 nucleocapsid (N) protein to both the 5'- and 3'-ends of genomic RNA has different implications arising from its binding to the central region during virion assembly. However, the mechanism underlying selective binding remains unknown. Herein, we performed the high-throughput RNA-SELEX (HTR-SELEX) to determine the RNA-binding specificity of the N proteins of various SARS-CoV-2 variants as well as other {beta}-coronaviruses and showed that N proteins could bind two unrelated sequences, both of which were highly conserved across all variants and species. Interestingly, both these sequence motifs are virtually absent from the human transcriptome; however, they exhibit a highly enriched, mutually complementary distribution in the coronavirus genome, highlighting their varied functions in genome packaging. Our results provide mechanistic insights into viral genome packaging, thereby increasing the feasibility of developing drugs with broad-spectrum anti-coronavirus activity by targeting RNA binding by N proteins.
RESUMO
Objective To investigate the effects of cyclic stretch on migration of MC3T3-E1 cells and its related mechanism. Methods The strain loading system was used to stretch MC3T3-E1 cells cultured in vitro with 15% amplitude, to simulate the mechanical condition in vivo. The wound healing assay was used to detect the migration of MC3T3-E1 cells. Western blotting was used to test Runx2 expression. RNA interfering was used to decrease Runx2 expression. Results Cyclic mechanical stretch with 15% amplitude, 1.25 Hz frequency and lasting for 24 hours could promote the migration of MC3T3-E1 cells and increase the expression level of Runx2. Runx2 interference inhibited the migration of MC3T3-E1 cells in static culture condition. Interference with Runx2 expression in MC3T3-E1 cells could partially reduce the positive effect of cyclic mechanical stretch on cell migration. Conclusions Cyclic stretch can promote the migration of MC3T3-E1 cells, and Runx2 may play an important role in this process. This study provides experimental basis for finding innovative clinical treatment method to promote fracture healing.
RESUMO
Objective To investigate the synergistic effects of pathologically elevated cyclic stretch and platelet-derived microvesicles (PMVs) on migration of vascular smooth muscle cells (VSMCs) and the potential role of calcium in this process. Methods The FX-5000T strain loading system was used to apply cyclic stretch to VSMCs with magnitudes of 5% and 15%, which simulated physiological and hypertensive situation respectively in vitro; wound healing assay was used to analyze VSMCs migration; Ca2+-free medium was used to remove extracellular calcium; 2-APB (an antagonist of IP3R) was used to inhibit the release of intercellular stored calcium; GSK219 (an antagonist of TRPV4) and Nifedipine (an inhibitor of L-type voltage-gated calcium channel) were applied to block the activity of respective calcium channel; thrombin was used to stimulate platelets in vitro which simulated the hypertensive activation of PMVs in vivo. ResultsCompared with 5% cyclic stretch, 15% cyclic stretch significantly promoted VSMC migration. Removal of extracellular calcium inhibited VSMCs migration, but the application of GSK219 and Nifedipine did not affect the migration up-regulated by 15% cyclic stretch; while 2-APB which inhibited the release of intracellular stored calcium could also repress VSMCs migration under 15% cyclic stretch. PMVs further promoted VSMC migration under 15% cyclic stretch condition, and both extracellular calcium and intercellular stored calcium were involved in this process. Conclusions Both intracellular and extracellular calcium play important roles in VSMC migration induced by 15% cyclic stretch, and PMVs synergistically participate in the above process. The study is aimed to provide new mechanobiological insights into the molecular mechanism and clinical targets of vascular remodeling in hypertension.
